Astronomy & Space
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▷ Astronomy
  1. A cloud, gentle and ghostlike, drifts overhead like nature's quiet reverie—yet hidden within its misty embrace lies a staggering truth: it weighs over a million tonnes. That's the heft of 200,000 elephants suspended in a skybound sponge stretching a cubic kilometer wide. And still, it floats. its density is just 0.4% lighter than the surrounding air—and the lift of warm updrafts, this colossal vapor mass defies gravity with elegance. A cloud isn't just beautiful; it's a silent powerhouse, gliding above us with the grace of something far lighter than it truly is.
  2. Astronomy, the study of celestial objects and phenomena, is one of the oldest fields of human inquiry, with evidence of astronomical observations dating back tens of thousands of years. Long before it became a formal scientific discipline, humans in prehistoric times were already observing the night sky, tracking the movements of stars, planets, and lunar phases for navigation, agriculture, and spiritual purposes. While modern astronomy—grounded in physics and mathematics—is relatively recent, our fascination with the cosmos is deeply rooted in human history and culture.
  3. Early astronomical records trace back to the Babylonians, with surviving texts like the MUL.APIN dating to around 1200 BCE, and systematic observations beginning by 750 BCE, laying the foundation for mathematical astronomy. Interest in celestial phenomena was also evident in ancient Chinese, Central American, and North European cultures. The Chinese developed sophisticated calendars and observatories as early as 2300 BCE, linking celestial events to imperial governance through the Mandate of Heaven. Central American civilizations, such as the Maya, created precise calendars and tracked planetary movements for agricultural and ritual purposes. In Northern Europe, structures like Stonehenge and artifacts such as the Nebra sky disk (c. 1600 BCE) suggest astronomical alignments and early sky mapping. Across these cultures, astronomy served practical, spiritual, and political roles, including timekeeping, navigation, agriculture, and divination, making it one of humanity's earliest scientific endeavors.
  4. The word astronomy originates from the Greek term ἀστρονομία, which combines ἄστρον (astron), meaning "star," and νόμος (nomos), meaning "law" or "culture." Thus, astronomy can be translated as the "law of the stars" or, depending on interpretation, the "culture of the stars". This etymology reflects the discipline's ancient roots in observing and understanding celestial patterns, which early civilizations used to regulate calendars, navigation, and spiritual beliefs.
  5. Astronomers have recently made a series of remarkable discoveries that deepen our understanding of the cosmos. They identified a rare distant object, 2020 VN40, orbiting in perfect sync with Neptune, offering new insights into the dynamics of the outer solar system. In a young star's disk, they uncovered a monster-sized exoplanet, up to ten times the size of Jupiter, previously hidden in a swirl of gas and dust. They also confirmed the existence of a fossil galaxy, KiDS J0842+0059, located 3 billion light-years away, which has remained virtually unchanged for 7 billion years, acting as a cosmic time capsule. Adding to the intrigue, astronomers discovered three new moons—one around Uranus and two around Neptune, some of the faintest ever detected. Perhaps most dramatic is the detection of a planet rapidly disintegrating, BD+05 4868 Ab, shedding a comet-like tail of minerals as it orbits its star every 30.5 hours, and predicted to vanish within 1–2 million years. These findings showcase the extraordinary diversity and dynamism of our universe.
  6. Astronomers began seriously searching for Planet Nine after compelling evidence of its existence was unveiled on January 20, 2016 by researchers at Caltech. This hypothetical super-Earth-sized planet is estimated to have a mass about 10 times that of Earth, a diameter two to four times larger, and a mass roughly 5,000 times that of Pluto. It is believed to follow a highly elongated orbit that lies far beyond Neptune, taking approximately 10,000 to 20,000 years to complete a single revolution around the Sun. Though it has not yet been directly observed, its gravitational influence appears to explain the unusual clustering of orbits among distant trans-Neptunian objects, suggesting that a substantial and still-hidden member of our solar system may be shaping the outer reaches of planetary space.
  7. Astronomers have recently discovered a potential new dwarf planet in the outer reaches of our solar system, named 2017 OF201. This celestial body has an extreme orbit, taking 25,000 years to complete a single trip around the Sun. It is estimated to be about one-third the size of Pluto and may challenge the hypothesis of a hidden ninth planet beyond Neptune. Scientists suggest that the Kuiper Belt and beyond may not be as empty as previously thought. The object's orbit is highly elongated, bringing it as close as 4.14 billion miles from the Sun and as far as 157 billion miles away. Below are some newly found planets. These discoveries highlight the ongoing exploration and understanding of planets beyond our solar system.
    • Six new exoplanets have been discovered, including HD 36384 b, TOI-198 b, TOI-2095 b, TOI-2095 c, TOI-4860 b, and MWC 758 c, bringing the total confirmed exoplanets to 5,502.
    • Two new rocky planets, HD 260655 b and HD 260655 c, are among the closest-known rocky planets found outside our solar system.
    • Four small planets have been confirmed around Barnard's Star, which is one of the closest stars to Earth.
    • A super-Earth has been confirmed in the habitable zone of a nearby Sun-like star.
  8. Astronauts do get temporarily taller in space due to spinal elongation caused by the microgravity environment. In the absence of Earth's gravity, the spinal vertebrae decompress and expand, allowing astronauts to grow up to 3% taller—which translates to about 2 inches (5 centimeters) for someone who is 6 feet tall. However, this change is not permanent. Once astronauts return to Earth, the gravitational pull compresses their spines back to normal, and their height typically returns to its original measurement within a few months. This phenomenon has been well-documented by NASA and is part of ongoing research into the effects of space travel on the human body.
  9. Astronauts do not shower in space the way we do on Earth due to the lack of gravity and limited water supply. Instead, they maintain hygiene using rinseless liquid soap, no-rinse shampoo, and wet wipes. To clean themselves, astronauts typically use a wet washcloth to apply soap and water from pouches, then dry off with a towel. Any excess water tends to float in microgravity, so it's often captured by airflow systems to prevent it from interfering with equipment. This method is efficient and safe, and it allows astronauts to stay clean without the need for a traditional shower setup.
  10. Astronauts do not have traditional laundry facilities aboard the International Space Station (ISS). Instead, they follow a wear-and-discard system. Clothing is worn for extended periods—underwear for several days, and outer garments like shirts and pants for weeks—until they become too dirty or smelly. Workout clothes, which absorb sweat during daily exercise, are usually discarded after a week due to odor and stiffness. Once clothes are no longer usable, they are packed with other waste and loaded onto unmanned cargo spacecraft like Russia's Progress, which are then de-orbited to burn up in Earth's atmosphere. NASA is actively working on solutions for future long-duration missions, such as trips to Mars, where discarding clothes won't be feasible. In partnership with Tide, NASA is testing low-water, space-safe detergents that could allow astronauts to wash and reuse clothing in microgravity.
  11. In earlier decades, astronomers often referred to "Goldilocks worlds"—planets located in the habitable zone (HZ) of their stars, where conditions were thought to be "just right" for liquid water to exist on the surface. This zone is defined as the orbital region around a star where temperatures could allow water to remain in liquid form, a key ingredient for life as we know it. However, research over the past two decades has shown that being in the HZ does not guarantee habitability. Factors such as atmospheric composition, planetary mass, magnetic field strength, and stellar activity play critical roles in determining whether a planet can actually support life. For example, Venus and Mars both lie within the Sun's habitable zone, yet neither is currently habitable. This has led scientists to refine the concept of habitability beyond mere location, incorporating a broader range of geophysical and environmental criteria.
  12. The Universe is mostly invisible, with only about 4.9% composed of ordinary atoms—the stuff that makes up stars, planets, and everything we can see. The remaining 95.1% consists of dark matter (about 26.8%) and dark energy (around 68.3%), both of which are invisible and still largely mysterious to scientists. Dark matter exerts gravitational influence but doesn't emit light, while dark energy is thought to drive the accelerated expansion of the universe. Together, they dominate the cosmos, reminding us that most of what exists lies beyond the reach of our eyes and current understanding.
  13. The Universe is both vast and ancient. The observable universe spans an estimated 93 billion light-years in diameter and contains roughly two trillion galaxies, each housing billions of stars—comparable to the 100–400 billion stars found in our own Milky Way. Despite its immense scale, the universe has a surprisingly knowable age: it's estimated to be about 13.8 billion years old, dating back to the Big Bang. These staggering numbers highlight the sheer enormity and deep history of the cosmos we inhabit.
  14. The Universe is full of strange and surprising phenomena. The Milky Way is believed to carry a scent reminiscent of rum and raspberries, thanks to molecules like ethyl formate and other alcohol-like compounds drifting through space. On Venus, a single day lasts longer than a year—its slow rotation takes 243 Earth days, while its orbit around the Sun takes just 225 days. Meanwhile, Uranus spins on its side, a peculiar tilt likely caused by a massive ancient collision. Over on Jupiter, the iconic Great Red Spot—a colossal storm larger than Earth—has been raging for centuries, though it has been noticeably shrinking in recent decades. These oddities remind us that the cosmos is not only vast, but also wonderfully weird.
  15. The Universe encompasses everything that exists—space, matter, and energy—and while it's unimaginably vast, we can only observe a portion of it known as the observable universe, which spans about 93 billion light-years in diameter. Within this expanse are over two trillion galaxies, each a massive system of stars, gas, dust, and dark matter bound by gravity. Our own solar system resides in the Milky Way, a spiral galaxy estimated to contain between 100 and 400 billion stars. The universe is not static; it's expanding, with galaxies drifting farther apart over time. This expansion is accelerating, a phenomenon scientists attribute to the mysterious force known as dark energy. Adding to the cosmic tapestry is the cosmic microwave background radiation, a faint glow that serves as the lingering afterglow of the Big Bang, offering clues to the universe's earliest moments.
  16. The Universe is filled with mind-boggling numbers that stretch the limits of imagination. All the other planets in our solar system could fit in the space between Earth and the Moon, a gap of about 238,855 miles. Beyond our planetary neighborhood, the cosmos holds an almost unfathomable abundance—more stars exist than grains of sand on all of Earth's beaches and deserts combined. And even our nearest stellar neighbor, Proxima Centauri, is staggeringly distant: traveling there at a steady 70 mph would take over 356 billion years, far exceeding the current age of the universe. These figures highlight just how immense and incomprehensibly vast our universe truly is.
  17. The oldest observable thing in the Universe is the cosmic microwave background (CMB) radiation, which is the faint afterglow of the Big Bang, dating back to about 380,000 years after the Universe began. Though not a physical object, the CMB represents the earliest light we can detect, offering a snapshot of the Universe when it first became transparent to radiation. Older than the CMB, but not directly observable, is the initial singularity—a theoretical point of infinite density and temperature from which the Universe is thought to have expanded. However, modern cosmology suggests that cosmic inflation may have preceded the Big Bang, and the singularity itself might not have been a real physical state, but rather a mathematical extrapolation beyond the limits of known physics.
  18. The Universe is filled with bizarre and awe-inspiring phenomena, from terrifying cosmic forces to the strangest planetary oddities. Among the scariest things are rogue black holes, incoming megacomets, and the eventual collision between the Milky Way and Andromeda galaxies, all of which remind us how dynamic and dangerous space can be. Then there are the weirdest planets, like WASP-76b, where it rains molten iron, 55 Cancri e, a possible diamond planet, and J1407b, dubbed "Super Saturn" for its colossal ring system3. Even within our own solar system, oddities abound—Uranus spins sideways, Iapetus has a stark two-tone surface, and Titan hides lakes beneath its icy crust. Add to that the interstellar visitor 'Oumuamua, whose origin and shape remain mysterious, and you've got a cosmic lineup that's as eerie as it is fascinating. As for stars, the Universe hosts hypervelocity stars, infrared-only pulsars, and ancient stars like HD 140283, which challenge our understanding of cosmic time5. Together, these phenomena paint a picture of a Universe that's not just vast—but deeply strange and endlessly captivating.
  19. The Universe is overwhelmingly composed of dark matter and dark energy, two mysterious substances that together account for about 95% of its total mass and energy. Dark matter, which makes up roughly 27%, doesn't emit or absorb light but exerts gravitational influence, helping to hold galaxies together. Dark energy, comprising about 68%, is even more enigmatic—it's believed to drive the accelerated expansion of the universe. Despite their dominant presence, both remain poorly understood, and uncovering their true nature is one of the biggest challenges in modern cosmology.
  20. The ultimate fate of the Universe remains one of the most profound questions in cosmology, with several competing theories. The most widely accepted scenario is the Big Freeze (or heat death), in which the Universe continues to expand forever, gradually cooling as stars burn out and energy becomes evenly distributed, leading to a dark, lifeless cosmos. Another possibility is the Big Rip, where dark energy accelerates expansion so violently that galaxies, stars, and even atoms are eventually torn apart. Though less favored today, the Big Crunch—where gravity reverses expansion and the Universe collapses back into a dense singularity—was once a leading theory, and some models still explore its feasibility. These outcomes span timescales from tens of billions to up to 10⁷⁸ years, depending on the nature of dark energy and the Universe's geometry. While we can't predict the end with certainty, ongoing observations continue to refine our understanding of cosmic destiny.
  21. One of the most astonishing and unsettling facts about the Universe is how little of it we truly understand. According to data from missions like ESA's Planck and NASA's cosmological studies, only about 4.9% of the Universe is made up of ordinary matter—the atoms that form stars, planets, and everything we can see. The rest is composed of mysterious, invisible components: roughly 26.8% is dark matter, which exerts gravitational influence but does not emit or absorb light, and about 68.3% is dark energy, a force responsible for the accelerated expansion of the Universe. These two enigmatic substances dominate the cosmos, yet remain among the greatest puzzles in modern astrophysics.
  22. As of 2024, observational evidence—including data from missions like Planck, WMAP, and BOOMERanG—suggests that the observable Universe is spatially flat, meaning it follows the rules of Euclidean geometry: parallel lines remain parallel, and the angles of a triangle add up to 180 degrees. This flatness is inferred from measurements of the cosmic microwave background and the universe's density and expansion rate, which appear to be finely balanced. However, the global structure of the universe remains unknown; it could be finite or infinite, simply connected like Euclidean space or multiply connected like a torus. In a small closed universe, for example, light could loop around, producing multiple images of the same object, though not necessarily of the same age. While space may be locally flat, its topology on the largest scales is still a profound mystery.
  23. Orbits around black holes are a mesmerizing dance through warped spacetime, governed not by Newton's laws but by the elegant equations of general relativity. Unlike the predictable ellipses traced by planets, these paths can twist and precess due to the immense curvature near the event horizon. The innermost stable circular orbit marks the last safe haven before matter spirals into oblivion, and around rotating black holes, frame-dragging effects can even twist the orbital plane itself. Observations of stars like S0-2 circling the supermassive black hole at the heart of the Milky Way have confirmed these predictions, revealing subtle shifts that only Einstein's theory can explain. In this cosmic ballet, gravity becomes geometry, and motion becomes a probe into the very fabric of the universe.
  24. Black holes come in wildly different sizes, stretching the imagination from cosmic giants to compact enigmas. Supermassive black holes, lurking at the centers of galaxies, can span tens of millions of kilometers and weigh billions of times more than our Sun. These gravitational behemoths sculpt the motion of stars and bend light itself. But not all black holes are so colossal. Stellar-mass black holes, born from the collapse of massive stars, can be astonishingly small—some barely larger than a city. In 2019, astronomers identified one with a diameter of just 19 kilometers, a speck of darkness with the mass of a star compressed into a space smaller than Manhattan. Despite their size, these tiny titans warp spacetime with such intensity that not even light can escape their grasp.
  25. Despite their reputation for cosmic destruction, black holes exert gravity just like any other massive object—no more, no less. A black hole with ten times the mass of the Sun pulls with the same force as a ten-solar-mass star, meaning that nearby objects would orbit it in precisely the same way. In fact, stable orbits around black holes are not only possible, they're observed throughout the universe. Some scientists even speculate that life could exist on planets circling these dark giants, drawing energy from the intense radiation of their accretion disks. The idea isn't just theoretical—popular science fiction has explored it, imagining worlds where time bends and light dances at the edge of oblivion.
  26. Black holes may be invisible, but they leave behind unmistakable footprints in the cosmos. Their gravity is so intense that once light crosses the event horizon—the infamous point of no return—it's lost forever, as the escape velocity exceeds even the speed of light. Yet astronomers have found clever ways to detect these cosmic phantoms. In 2002, the star S2 was observed whipping around an unseen object at the heart of the Milky Way, revealing the presence of Sagittarius A, a supermassive black hole. Then came a historic breakthrough in 2019, when the Event Horizon Telescope—a global network of synchronized radio observatories—captured the first-ever image of a black hole's shadow. The subject was M87, a supermassive black hole 55 million light-years away, encircled by a glowing accretion disk of gas and dust spiraling inward at near-light speeds. This disk, heated by friction and emitting powerful radiation, outlined the black hole's silhouette in a fiery ring, offering humanity its first direct glimpse into the abyss.
  27. Black holes are less like cosmic vacuum cleaners and more like gateways to the unknown—regions where gravity reigns supreme and the familiar rules of physics begin to unravel. While they trap anything that crosses the event horizon, including light, they aren't literal holes in spacetime but rather dense concentrations of mass that warp the geometry around them. What lies inside remains one of the greatest mysteries in astrophysics. Theoretical models suggest a singularity at the core, a point of infinite density where space and time cease to behave normally. Yet some physicists entertain the tantalizing possibility that black holes might be connected to other regions of the universe via wormholes—hypothetical tunnels through spacetime that could, in theory, allow travel across vast cosmic distances or even between universes. Though these ideas remain speculative, they offer a glimpse into the kind of mind-bending possibilities that emerge when general relativity meets quantum mechanics.
  28. Black holes are anything but stationary—they roam the cosmos like celestial nomads, shaped by the same gravitational dynamics that govern stars and planets. In 2015, this mobility was spectacularly confirmed when the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves rippling through spacetime, the aftermath of two black holes locked in a death spiral. These giants, with masses of 29 and 36 times that of the Sun, orbited each other for eons before colliding at nearly half the speed of light, releasing a burst of energy equivalent to three solar masses in the form of gravitational waves. The resulting signal, dubbed GW150914, marked the first direct observation of these elusive ripples and opened a new window into the universe. Far from being cosmic sinkholes, black holes are dynamic, powerful, and capable of shaking the very fabric of reality.
  29. The notion of black holes as cosmic shortcuts is a captivating blend of science and speculation. While most would obliterate anything that dares cross their event horizon, some physicists propose that large, rotating black holes might harbor "weak" singularities—regions where the destructive tidal forces are surprisingly gentle. This opens the door to the possibility of wormholes: theoretical tunnels through spacetime that could link distant galaxies or even parallel universes. In 2015, models suggested that a spacecraft might survive a plunge into a rotating black hole, potentially emerging elsewhere in the cosmos. Though no evidence yet confirms the existence of such portals, the idea continues to fuel both scientific inquiry and the imagination, offering a glimpse into a universe where the boundaries of space and time are not as rigid as once believed.
  30. Spaghettification is as dramatic as it sounds—a gruesome fate reserved for anything venturing too close to a black hole. This phenomenon arises from extreme tidal forces, where gravity's pull varies so sharply over short distances that the difference between the force on the feet and the head becomes catastrophic. As the body falls feet-first, the lower half is yanked harder than the upper, stretching it into a long, thin filament while simultaneously compressing it horizontally. The result is a grotesque transformation into a noodle-like shape, torn apart atom by atom. Interestingly, the severity of spaghettification depends on the black hole's size; smaller stellar-mass black holes produce more intense tidal gradients near the event horizon, making the effect more lethal than in their supermassive counterparts. So while the crushing density might seem like the main threat, it's really gravity's uneven grip that delivers the final twist.
▷ Space
  1. Space may seem silent, but it's not completely so—sound can travel through certain mediums like plasma, allowing faint noises to ripple through the cosmos. The Moon, far from being perfectly round, is actually lemon-shaped due to tidal forces and its early molten state. The Milky Way carries a curious aroma of rum, raspberries, and booze, thanks to molecules like ethyl formate drifting in interstellar clouds. On Mercury, a single day lasts twice as long as its year, with its slow rotation taking 176 Earth days compared to its 88-day orbit around the Sun. And in a fun twist of cosmic geometry, all the other planets in the solar system could fit in the space between Earth and the Moon, emphasizing both the vastness and the strangeness of our celestial neighborhood.
  2. Space is a vast vacuum, meaning it's essentially empty and silent, with temperatures plunging to -270.45°C (-454°F) in some regions. The Sun, a massive star, is large enough to fit about 1.3 million Earths inside it. The universe is constantly expanding, and within it, the Milky Way galaxy—just one of billions—contains hundreds of billions of stars. Orbiting Earth is a growing cloud of space junk, including used rockets and defunct satellites, posing challenges for future missions. Astronauts rely on spacesuits to survive, which provide oxygen, pressure, and temperature control. The Moon plays a crucial role in generating Earth's tides, and footprints left by astronauts on its surface may remain for millions of years due to the lack of wind and water. On Venus, a single day lasts longer than its year, adding to the planet's bizarre characteristics.
  3. Space is a near-perfect vacuum, meaning it contains almost no matter—no air, no atmosphere, and no medium through which sound waves can travel. Because sound requires a material like air, water, or solid to propagate, it cannot exist in the vacuum of space. The boundary of outer space is commonly defined by the Kármán line, located about 100 kilometers (62 miles) above Earth's surface, where the atmosphere becomes too thin to support conventional flight. Beyond this altitude, the shell of air surrounding our planet effectively disappears, marking the transition from Earth's atmosphere to the silent expanse of space.
  4. Space is full of astonishing facts that defy everyday experience. For instance, if two pieces of the same metal touch in the vacuum of space, they can fuse together permanently through a process called cold welding, because there's no atmosphere to form a protective oxide layer. The Pistol Star, one of the brightest known stars in our galaxy, shines with a luminosity 10 million times greater than the Sun3. Speaking of the Sun, it contains a staggering 99.86% of the solar system's total mass, dwarfing all the planets combined. And in a fun twist of cosmic geometry, all the other planets—from Mercury to Neptune—can fit side by side in the space between Earth and the Moon, but only when the Moon is at its farthest point, or apogee.
  5. Space, or outer space, is a near-perfect vacuum, meaning it contains extremely low densities of matter but is not entirely empty. It is permeated by the interstellar medium, a sparse mixture of hydrogen and helium atoms, cosmic dust, and ionized gases, which fills the space between stars and galaxies. Space also contains various forms of radiation, including cosmic rays and the cosmic microwave background, as well as magnetic fields generated by celestial bodies. Despite this, the vast majority of the universe's mass-energy is composed of dark matter and dark energy, which together account for about 95% of the total content of the cosmos. These components are invisible and not yet fully understood: dark matter acts as a gravitational scaffold for galaxies, while dark energy drives the accelerating expansion of the universe.
  6. Space appears black because it is a near-perfect vacuum, containing very little matter to scatter light. Unlike Earth's atmosphere, which diffuses sunlight and creates a blue sky, space lacks the particles needed for such scattering. Although trillions of stars emit light across the universe, their glow does not fill space with brightness due to the vast distances involved and the phenomenon of cosmological redshift—as the universe expands, light from distant stars is stretched to longer wavelengths, often beyond the visible spectrum. Additionally, the finite age of the universe means that light from the most distant stars has not yet reached us, a resolution to Olbers' Paradox. As a result, the night sky remains overwhelmingly dark, punctuated only by the scattered light of nearby stars and galaxies.
  7. Space itself doesn't have a smell in the traditional sense, since it's a vacuum and lacks air molecules to carry scent. However, astronauts returning from spacewalks have consistently reported a distinct odor clinging to their spacesuits and equipment. This smell is often described as a mix of burnt metal, welding fumes, gunpowder, and ozone, with occasional sweet undertones. The scent likely results from atomic oxygen and high-energy particles interacting with suit materials during exposure to space, triggering chemical reactions that produce these odors. Additionally, polycyclic aromatic hydrocarbons (PAHs)—organic molecules common in space—may contribute to the burnt or smoky aroma astronauts notice upon reentering their spacecraft.
  8. Although space is often described as silent due to the lack of air or any medium for sound waves to travel through, it is far from empty or inactive. The cosmos is alive with electromagnetic radiation—including radio waves, X-rays, and gamma rays—that can be detected by scientific instruments, even if they're inaudible to human ears. Space also teems with charged particles, solar wind, and cosmic rays, all streaming across vast distances at incredible speeds. So while space may lack traditional sound, it resonates with energy, motion, and invisible signals that reveal a dynamic and vibrant universe.
  9. There is no sound in space as we experience it on Earth because sound requires a medium—such as air, water, or solid matter—to travel. Space is a vacuum, meaning it is mostly empty and lacks the particles needed for sound waves to propagate. Without a medium to carry vibrations, sound cannot travel through the vast emptiness of space. While certain regions, like dense gas clouds or plasma, can transmit limited vibrations, the majority of space remains silent, making it eerily quiet compared to our sound-filled world.
  10. Speaking in space without assistance is impossible because space is a vacuum, lacking the air or other material medium needed for sound waves to travel. Sound requires particles to propagate, and in the emptiness of space, there are too few to carry vibrations from one source to another. However, astronauts can still communicate using technology, specifically radio systems built into their spacesuits and spacecraft. These systems convert voice into radio waves, which do not require a medium and can travel through the vacuum of space. During spacewalks or operations outside the spacecraft, astronauts rely on these radio communications to talk to each other and to mission control, ensuring safety and coordination despite the silence of the cosmos.
  11. The question of whether space is endless or truly infinite remains open in science. While the observable universe—the part we can see and measure—is finite, spanning about 93 billion light-years in diameter, the overall size and shape of the universe are still unknown. Some cosmological models and evidence suggest the universe could be infinite, extending forever beyond our observational limits. Others propose it may be finite but unbounded, meaning space curves back on itself like the surface of a sphere, with no edges or boundaries. Until more data emerges, the true nature of the universe's extent remains one of the most profound mysteries in cosmology.
  12. Aging still occurs in space, but under specific conditions, it can proceed slightly more slowly due to time dilation, as described by Einstein's theory of relativity. Astronauts aboard the International Space Station (ISS) experience two competing relativistic effects: gravitational time dilation, which tends to accelerate aging due to reduced gravitational influence, and velocity-based time dilation, which slows aging because of their high orbital speed. On the ISS, the velocity effect outweighs the gravitational one, resulting in astronauts aging marginally more slowly—by approximately 0.005 to 0.007 seconds over a six-month mission. However, spaceflight also introduces biological stressors such as microgravity, cosmic radiation, and musculoskeletal degradation, which can mimic or intensify certain aging processes. Thus, while time passes more slowly from a relativistic standpoint, the physiological experience of aging in space remains complex.
  13. Several exoplanets are considered potentially habitable, meaning they lie within their stars' habitable zones where liquid water could exist—a key ingredient for life as we know it. Among the most promising candidates are K2-18b, Gliese 12 b, and TOI-715 b. K2-18b, a sub-Neptune located about 124 light-years away, has drawn particular interest due to the James Webb Space Telescope's detection of methane and carbon dioxide in its atmosphere, suggesting a water-rich interior, though water vapor remains elusive and signs of life are unconfirmed. Gliese 12 b, located just 40 light-years from Earth, is slightly smaller than our planet and may have a temperate surface, but its atmosphere—crucial for habitability—has yet to be confirmed. TOI-715 b, discovered by TESS, is a super-Earth in the conservative habitable zone of a red dwarf star and is considered one of the best candidates for future atmospheric studies. These worlds offer exciting opportunities to explore the conditions that might support life beyond Earth.
  14. The Big Bang theory is the leading explanation for the origin of the universe, which is estimated to be about 13.8 billion years old. Because of the vast distances involved, light from some galaxies takes billions of years to reach us, allowing us to glimpse the distant past. The universe is composed largely of dark matter (about 27%) and dark energy (around 68%), both mysterious and invisible forces that shape its structure and expansion. Among the largest known formations is the Hercules–Corona Borealis Great Wall, a colossal galactic superstructure. The universe also hosts quasars, the brightest and most powerful objects, fueled by supermassive black holes. Despite its richness, the universe is mostly empty space, yet it is constantly changing and evolving. One of its most extreme products are neutron stars, incredibly dense remnants of massive stars that collapsed after supernova explosions. These phenomena reveal the dynamic and awe-inspiring nature of the cosmos.
  15. The Big Bang theory explains the origin of the cosmos, marking the beginning of space and time. Based on measurements of the universe's expansion rate, scientists estimate its age to be about 13.8 billion years, a figure supported by observations of the cosmic microwave background and distant galaxies. However, a controversial new study proposes an alternative model suggesting the universe could be as old as 26.7 billion years, using a hybrid of expansion theory and the "tired light" hypothesis to explain anomalies like mature galaxies appearing too early in cosmic history4. While intriguing, this idea is not widely accepted and challenges the standard cosmological model, which remains the prevailing framework in astrophysics.
  16. In Big Bang models of physical cosmology, the age of the universe is defined as the cosmological time elapsed since the moment when the scale factor—which describes the expansion of space—extrapolates to zero, marking the theoretical beginning of the universe. Based on modern observations and models, including data from the cosmic microwave background and expansion rates, scientists currently estimate the universe to be about 13.79 billion years old. This age reflects our best understanding of cosmic history from the Big Bang to the present.
  17. The oldest black hole discovered to date is estimated to be 13.2 billion years old, having formed approximately 470 million years after the Big Bang. This ancient black hole resides in the distant galaxy UHZ1, and its light has traveled across the cosmos for 13.2 billion years to reach us. Detected through a combination of data from the James Webb Space Telescope and Chandra X-ray Observatory, it emits X-rays—a clear signature of active accretion, meaning it is still growing by consuming surrounding matter. Because of its intense brightness and energetic emissions, it is classified as a quasar, a type of active galactic nucleus powered by a supermassive black hole. This discovery not only confirms that supermassive black holes existed in the early universe, but also challenges existing theories about how such massive objects could form so quickly after the Big Bang.
  18. Black holes are regions of space with incredibly dense mass and gravitational pull so strong that nothing—not even light—can escape once it crosses the event horizon, the boundary surrounding the black hole. Formed from the remnants of massive stars that collapse under their own gravity, black holes warp space and time around them, making them some of the most extreme and mysterious objects in the universe. Their presence is often detected indirectly through their effects on nearby matter and light, such as the bending of light or the acceleration of surrounding stars.
  19. The cosmic microwave background (CMB) radiation reveals the lingering afterglow of the Big Bang, offering a glimpse into the universe's infancy nearly 13.8 billion years ago. This faint, uniform microwave signal permeates all of space and captures a snapshot of the cosmos just 380,000 years after its birth—when atoms first formed and light was finally able to travel freely. Subtle temperature fluctuations within the CMB provide compelling evidence for the Big Bang theory and serve as a cosmic blueprint, helping scientists unravel the early conditions, structure, and evolution of the universe.
  20. The Boomerang Nebula, located about 5,000 light-years from Earth in the constellation Centaurus, is the coldest known natural object in the universe. Its temperature has been measured at around 1 Kelvin (−272.15°C), which is colder than the Cosmic Microwave Background (CMB)—the residual glow from the Big Bang that sets the average temperature of space at about 2.725 Kelvin (−270.4°C). This extreme cold is caused by a rapidly expanding outflow of gas from a dying red giant star, possibly triggered by a smaller companion star plunging into it, ejecting material at speeds far beyond what a single star could produce. The Boomerang Nebula is so cold that it even absorbs the CMB radiation, making it the only known object colder than the background temperature of space itself.
  21. Scientists theorize that a planet made largely of diamond may exist, with the most famous candidate being 55 Cancri e, an exoplanet located about 40 light-years away in the constellation Cancer. This scorching super-Earth is roughly twice the size of Earth and eight times its mass, orbiting so close to its host star that a year lasts only 18 hours. Due to its high density and the carbon-rich composition of its parent star, researchers suggest that its interior could be composed largely of diamond and graphite, potentially making up a third of its mass. Though it sounds like science fiction, this dazzling possibility is rooted in serious astrophysical modeling and reveals just how exotic and diverse planetary systems beyond our own can be.
  22. The International Space Station (ISS) is the third brightest object in the sky, outshone only by the Sun and the Moon. Orbiting Earth at an altitude of about 400 kilometers, the ISS reflects sunlight and can be easily seen with the naked eye as a fast-moving, bright white dot crossing the sky—especially shortly after sunset or before sunrise. Its visibility and brilliance make it a striking reminder of human achievement in space exploration and international cooperation.
  23. A full NASA spacesuit can cost up to $12 million, reflecting the extraordinary engineering required to protect astronauts from the harsh conditions of space, including temperature extremes, radiation, and micrometeorites. Meanwhile, on Mars, sunsets appear blue rather than red due to the planet's thin atmosphere and fine dust particles, which scatter sunlight differently than Earth's atmosphere. These particles allow blue light to penetrate more efficiently, creating a surreal, bluish glow around the setting Sun. Together, these facts highlight both the ingenuity of space exploration and the alien beauty of other worlds.
▷ Planets
  1. The outer planets of our solar system are full of fascinating features. Mars, often called the "Red Planet," gets its distinctive hue from iron oxide—or rust—on its surface. Jupiter is the largest planet, and despite its massive size, it has a day lasting only about 10 hours due to its rapid rotation. Saturn is renowned for its stunning rings made of ice and rock, while Uranus and Neptune are classified as ice giants because of their cold temperatures and icy compositions. Together, Jupiter, Saturn, Uranus, and Neptune make up the four giant planets of our solar system. Most planets have moons orbiting them, but Jupiter holds the record, with the most moons discovered so far—over 90 and counting. These planetary giants showcase the diversity and grandeur of our solar system's architecture.
  2. Our solar system contains a variety of small celestial bodies, including asteroids, some of which are large enough to have their own moons. Saturn's rings, among the most iconic features in the solar system, are composed of countless pieces of ice and rock, ranging from tiny grains to house-sized chunks. Dwarf planets are smaller than regular planets but are round in shape, meeting some of the criteria for planethood. Recognized dwarf planets include Ceres, Pluto, Haumea, Makemake, and Eris. Pluto, once classified as the ninth planet, was redefined as a dwarf planet in 2006. Its largest moon, Charon, is unusually large compared to Pluto itself, making the pair more like a binary system. These small worlds and rocky remnants add depth and complexity to our understanding of the solar system.
  3. Our solar system, located within the Milky Way galaxy, is made up of the Sun, eight planets, their moons, as well as dwarf planets, asteroids, and comets. At its center is the Sun, a star that provides the light and heat essential for life, and is about 109 times the diameter of Earth, composed primarily of hydrogen and helium. Mercury is the closest planet to the Sun, while Venus, despite being second, is the hottest planet due to its thick atmosphere trapping heat. A day on Venus is longer than its year, with its rotation taking more time than its orbit around the Sun. Earth stands out as the only planet known to support life, and it has one moon that influences tides and stabilizes its rotation. This intricate system showcases the diversity and complexity of our cosmic neighborhood.
  4. The English word "sun" originates from the Old English word sunne, which in turn derives from the Proto-Germanic root sunnōn. This root is shared across several Germanic languages, appearing as zon in Dutch and Sonne in German. Ultimately, the term traces back to the Proto-Indo-European root sawel- or suwen, which is associated with the concept of shining or light. These ancient linguistic connections reflect the sun's central role in human culture and language, with variations of the word appearing in many Indo-European tongues, often linked to brightness and illumination.
  5. The Sun is currently about halfway through its lifespan, having existed for approximately 4.6 billion years. As a G-type main-sequence star, it is expected to continue fusing hydrogen into helium in its core for a total of about 10 billion years. This means it has roughly 5 billion years remaining before undergoing significant changes. Once its core hydrogen is depleted, the Sun will expand into a red giant, potentially engulfing the inner planets, including Earth. After shedding its outer layers as a planetary nebula, the remaining core will contract into a white dwarf—a dense, dim stellar remnant that will gradually cool and fade over billions of years.
  6. The Sun is truly an incredible and vital part of the solar system.
    • Age: The Sun is about 4.5 billion years old and is classified as a yellow dwarf star.
    • Composition: The Sun is a hot bright ball of hydrogen and helium at the center of our solar system, and it is becoming increasingly hotter (or more luminous) with time; the Sun is primarily composed of hydrogen (about 75%) and helium (about 24%) with trace amounts of other elements.
    • Size and Mass: The Sun's diameter is approximately 864,000 miles (1,392,000 kilometers), making it about 100 times wider than Earth; about 1.3 million Earths could fit inside the Sun; the Sun accounts for 99.86% of the total mass of our solar system.
    • Distance from Earth: The Sun is about 93 million miles (150 million kilometers) away from Earth; this distance is known as an astronomical unit (AU) and is used to measure distances within our solar system.
    • Energy Production: The Sun's core temperature reaches about 27 million degrees Fahrenheit (15 million degrees Celsius); this intense heat enables nuclear fusion, where hydrogen atoms fuse to form helium, releasing vast amounts of energy.
    • Rotation: The Sun rotates on its axis, but not uniformly; its equator completes one rotation in about 25 Earth days while its poles take about 36 Earth days.
    • Solar Activity: The Sun exhibits various dynamic activities, including solar flares and coronal mass ejections; these events release significant energy and particles into space, sometimes affecting Earth's magnetic field and communication systems.
    • Lifecycle: Currently, the Sun is in the middle of its lifecycle; within around 5 billion years, it will expand into a red giant before shedding its outer layers and leaving behind a dense core known as a white dwarf.
  7. The Sun is actually white, not yellow, although it often appears yellow when viewed from Earth due to the effects of atmospheric scattering. Sunlight contains all visible wavelengths, which combine to form white light. However, as sunlight passes through Earth's atmosphere, shorter wavelengths like blue and violet are scattered more strongly by air molecules—a process known as Rayleigh scattering. This leaves the longer wavelengths—such as yellow, orange, and red—more dominant in the direct path to our eyes, giving the Sun its familiar yellowish hue from the ground. In contrast, astronauts observing the Sun from space see it as a brilliant white object, confirming that its true color is white.
  8. The Sun, though considered an average-sized star, is so massive that approximately 1.3 million Earths could fit inside it if compressed, or about 960,000 if they retained their spherical shape. For a long time, Earth was believed to be the only planet in our solar system with liquid water, a key ingredient for life. However, NASA has since provided compelling evidence that intermittent liquid water flows on Mars as well. Observations from the Mars Reconnaissance Orbiter revealed seasonal dark streaks—known as recurring slope lineae (RSL)—that appear to be caused by briny water seeping down Martian slopes during warmer periods. This discovery has reshaped our understanding of Mars and its potential to harbor life.
  9. The Sun is not an old star, but rather a middle-aged one, having formed about 4.6 billion years ago. It currently resides in the main sequence phase of its life cycle, steadily fusing hydrogen into helium in its core—a process that marks the most stable and enduring stage in a star's evolution. As a G-type main-sequence star, the Sun is expected to live for roughly 10 billion years, placing it at about the midpoint of its lifespan. With approximately 5 billion years remaining, it will eventually exhaust its hydrogen fuel, expand into a red giant, and ultimately shed its outer layers, leaving behind a dense white dwarf. While the Sun is no longer young, it's far from reaching the twilight of its stellar life.
  10. The Sun is believed to have formed about 4.6 billion years ago from a dense region within a giant molecular cloud, triggered by the explosion of a massive star. This hypothetical progenitor star has been named Coatlicue, after the Aztec goddess of life and death. Coatlicue is thought to have been at least 30 times the mass of the Sun, and its stellar winds and eventual supernova explosion enriched the surrounding nebula with short-lived radionuclides like aluminium-26, which are found in meteorites today. These elements, along with the shockwave from the explosion, likely compressed nearby gas and dust, initiating the formation of hundreds of stars—including our Sun.
  11. The Sun is considered an average-sized star in the universe. It has a diameter of about 1.39 million kilometers, which is 109 times wider than Earth, and a mass about 330,000 times greater than Earth's. While it's the largest object in our solar system, many stars are much larger. For example, Stephenson 2-18, UY Scuti, and Westerlund 1-26 are hundreds to thousands of times larger in radius than the Sun. On the other hand, there are also smaller stars, such as red dwarfs, which can be just a fraction of the Sun's size. So in the grand cosmic scale, our Sun is neither the biggest nor the smallest—it's somewhere in the middle.
  12. All the other planets in our solar system can fit side by side between Earth and the Moon—but only when the Moon is at its farthest point from Earth, known as apogee. The average distance to the Moon is about 384,400 kilometers, and when you add up the diameters of Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune, the total comes to roughly 380,000 kilometers, leaving just enough room for them to fit snugly in that space. This surprising fact offers a striking way to visualize both the scale of our solar system and the vast emptiness of space.
  13. There are many stars far larger than our Sun, especially in terms of radius. One of the most notable is UY Scuti, a red hypergiant located in the constellation Scutum, which has an estimated radius about 1,700 times greater than the Sun's. Other colossal stars include Westerlund 1-26, a red supergiant with a radius over 1,500 times that of the Sun; WOH G64, a yellow hypergiant in the Large Magellanic Cloud with a radius around 800 solar radii; and NML Cygni, another red hypergiant with a radius estimated between 1,000 and 1,600 times the Sun's. These stars are not necessarily the most massive, but their enormous volumes make them some of the largest known stars in the universe.
  14. The Moon likely formed about 4.5 billion years ago from a colossal collision between the early Earth and a Mars-sized protoplanet named Theia. This impact ejected vast amounts of debris into orbit, which eventually coalesced to form the Moon. Known as the giant impact hypothesis, this theory is supported by evidence such as the Moon's similar composition to Earth's crust, the high angular momentum of the Earth-Moon system, and computer simulations of early planetary formation. While alternative theories like fission, capture, and co-formation have been proposed, they fail to fully explain the Moon's characteristics and are less widely accepted.
  15. Footprints on the Moon, like those left by Apollo astronauts, can last for millions of years because the Moon has no atmosphere, meaning there's no wind, rain, or flowing water to erode or wash them away. The lunar surface remains largely unchanged, preserving marks in the dust almost perfectly. However, over extremely long timescales, these footprints may eventually be altered by micrometeorite impacts, solar wind, and cosmic radiation, which slowly wear down the surface. Still, in the absence of Earth-like weather and geological activity, these imprints are among the most enduring human artifacts in the solar system.
  16. In the Southern Hemisphere, the Moon flips its familiar face, turning the "Man in the Moon" upside down and revealing a shape that resembles a rabbit—a transformation that's more than just visual trickery. This celestial rotation, caused by viewing the Moon from the opposite side of Earth, has inspired rich cultural interpretations across the globe. In East Asian folklore, for instance, the dark lunar maria form the image of the Jade Rabbit, tirelessly pounding the elixir of life with a mortar and pestle. Same Moon, different lens—each hemisphere casting its own myth upon the night sky.
  17. The Moon, often seen as a silent sentinel in the night sky, is quietly undergoing a transformation: it's shrinking. Over the past several hundred million years, its radius has contracted by roughly 50 meters (164 feet), a subtle change driven by the cooling of its interior. As the Moon loses heat, its crust crumples to accommodate the reduced volume, forming thrust faults—cliff-like ridges that scar its surface like wrinkles on a drying fruit. These structural shifts trigger moonquakes, seismic events that can last far longer than earthquakes on Earth and may pose risks to future lunar missions. Particularly near the lunar south pole, where NASA plans to land astronauts, these quakes could cause landslides or damage equipment. The Moon may seem still, but beneath its surface, it's anything but dormant.
  18. The Moon is a rocky, cratered place, roughly a quarter the size of Earth and an average of 238,855 miles away.
    • Formation and Age: The Moon formed about 4.6 billion years ago, around the same time as the Earth.
    • Size and Distance: Earth has just one moon; the Moon is about one-quarter the size of Earth, with a diameter of 2,160 miles (3,476 kilometers); the Moon orbits Earth at an average distance of 238,900 miles (384,000 kilometers).
    • Visibility: The Moon can be seen with the naked eye most nights as it traces its 27-day orbit around our planet; the Moon does not shine with its own light, it simply reflects light coming from the Sun.
    • Synchronous Rotation: The Moon is tidally locked with Earth, meaning we always see the same side of it from our planet.
    • Gravity: The Moon's gravity is about one-sixth that of Earth's. This is why astronauts can take giant leaps on its surface.
    • No Atmosphere: The Moon has no atmosphere, which means there is no weather, and the sky always appears black.
    • Tides: The gravitational pull of the Moon causes the rise and fall of tides on Earth.
    • Drifting Away: The Moon is slowly drifting away from Earth at a rate of about 3.8 centimeters per year.
    • Lunar Quakes: The Moon experiences quakes, known as moonquakes, caused by the gravitational pull of Earth.
    • Exploration: Only 12 people, all American men, have walked on the Moon; the first was Neil Armstrong in 1969 during the Apollo 11 mission.
    • Natural Satellite: The Moon is Earth's only natural satellite and one that we can easily see most nights.
  19. Titan, Saturn's largest moon, offers a hauntingly Earth-like landscape—only it runs on methane instead of water. Beneath its thick, golden haze lies the only other world in the Solar System with stable liquid rivers, lakes, and seas on its surface, all sculpted by rainfall. But this rain isn't the familiar splash of water; it's liquid methane, falling from methane-rich clouds in a cycle eerily similar to Earth's hydrologic system. Methane evaporates, condenses into clouds, and pours down in frigid storms, carving valleys and filling polar lakes that shimmer like alien oceans. Titan's weather may be bitterly cold, but its dynamic methane cycle makes it one of the most geologically active and fascinating moons in the cosmos.
  20. Earth is the third planet from the Sun and the largest of the terrestrial planets, which include Mercury, Venus, Earth, and Mars; Earth is the only known planet to support life.
    • Name: The name Earth is at least 1,000 years old; all of the planets, except for Earth, were named after Greek and Roman gods and goddesses; however, the name Earth is a Germanic word, which simply means "the ground."; there are, of course, many names for our planet in the thousands of languages spoken by the people of the third planet from the Sun.
    • Liquid Water: Earth is the only known planet to have liquid water on its surface, which is essential for life.
    • Age and Formation: Earth formed about 4.54 billion years ago; life appeared around 3.8 billion years ago, and humans have been around for only about 6 million years.
    • Speedy Traveler: Earth orbits the Sun at an average speed of about 107,182 kilometers per hour (66,627 miles per hour).
    • Day and Year: A day on Earth is 23.9 hours long, and it takes 365.25 days to complete one orbit around the Sun, which is why we have a leap year every four years.
    • Tilt and Seasons: Earth's axis is tilted at 23.4 degrees, which causes the seasons; as Earth orbits the Sun, different parts of the planet receive varying amounts of sunlight; the rotation of the Earth is gradually slowing down.
    • Cosmic Dust: Earth receives between 100 and 300 metric tons of cosmic dust every day.
    • Exploration: Despite being covered by over 70% water, more than 95% of Earth's oceans remain unexplored.
    • Gravity: The gravity between the Earth and the Moon causes the tides on Earth; the Hudson Bay region in Canada has slightly less gravity than other parts of the planet, and the reasons behind this anomaly are unknown.
  21. Earth is constantly bombarded by space dust and meteorites, with tiny particles from space falling to the planet every day. These range from microscopic grains to larger rocks, most of which burn up harmlessly in the atmosphere as meteors. Scientists estimate that tens of thousands of tons of cosmic material reach Earth annually, contributing to our planet's geological and atmospheric evolution. While large impacts are rare, the continuous influx of space debris is a reminder of Earth's dynamic relationship with the cosmos.
  22. Earth is the only planet in our solar system with a single moon, and this Moon plays a crucial role in stabilizing Earth's axial tilt, or wobble. By doing so, it has helped maintain a relatively stable climate over thousands of years, reducing extreme variations that could otherwise occur. This stability has been vital for the development and sustainability of life, making the Moon not just a companion in the sky, but a key factor in Earth's long-term habitability.
  23. Earth is the only known planet with stable liquid water oceans on its surface, covering about 71% of the planet and playing a crucial role in sustaining life. While other celestial bodies—such as Europa, Enceladus, Titan, and even Pluto—are believed to harbor subsurface oceans beneath layers of ice or rock, these hidden reservoirs are vastly different from Earth's expansive and dynamic surface oceans. Earth's oceans are unique not only in their extent but also in their stability, maintained by a delicate balance of atmospheric pressure, temperature, and solar energy. These conditions make Earth's hydrosphere a rare and remarkable feature in the known universe.
  24. Earth's age—an astonishing 4.54 billion years—is etched into its oldest minerals and meteorites, revealed through the precision of radiometric dating. That makes our planet a relatively youthful member of the cosmic family: roughly half the age of the Milky Way Galaxy, which formed between 11 and 13 billion years ago, and about a third as old as the Universe itself, estimated to be between 13.8 and 15 billion years. Earth emerged long after the first stars lit up the void, yet early enough to witness the rise of life, continents, and civilizations—all within a blink of cosmic time.
  25. There are approximately 3 trillion trees on Earth, according to a comprehensive study led by Yale researchers, which used satellite imagery and ground-based inventories to map global tree density. This translates to roughly 422 trees per person, a figure far higher than earlier estimates. In comparison, our own galaxy—the Milky Way—is believed to contain between 100 and 400 billion stars, based on models that estimate stellar mass and distribution. These staggering numbers highlight both the richness of Earth's biosphere and the vastness of the cosmos, offering perspective on the scale of life and matter in the universe.
  26. Earth and Mars orbit the Sun; but Earth is closer to the sun, and therefore races along its orbit more quickly. Earth makes two trips around the Sun in about the same amount of time that Mars takes to make one trip.
  27. According to Universe Today, approximately 1.3 million Earths could fit inside the Sun, based on a comparison of their volumes. This staggering number highlights the Sun's immense size, which is about 109 times the diameter of Earth and accounts for 99.86% of the solar system's total mass. The calculation assumes the Earths are packed tightly without empty space, emphasizing just how vast and dominant our star is within the solar system.
  28. As of March 2025, Saturn holds the title for the most known moons in our solar system, with 274 confirmed natural satellites, according to NASA Science and Popular Science. This number surpasses Jupiter, which was previously thought to have the most moons. Saturn's moons are incredibly diverse, ranging from massive bodies like Titan, which is larger than Mercury, to numerous smaller, irregular moons that follow elliptical or even retrograde orbits. Many of these tiny moons are just a few kilometers across and are believed to be fragments of larger moons shattered by ancient collisions. Saturn's moon system continues to intrigue scientists and offers valuable clues about the evolution of the solar system.
  29. Mars is a fascinating planet and is often called the "Red Planet" because of its reddish appearance, which is due to iron oxide (rust) on its surface.
    • Thin Atmosphere: Mars has a very thin atmosphere composed mostly of carbon dioxide, with traces of nitrogen and argon.
    • Moons: Mars has two small moons, Phobos and Deimos, which are thought to be captured asteroids.
    • Size and Distance: Mars has a radius of about 2,106 miles (3,390 kilometers), making it roughly half the size of Earth. It is about 142 million miles (228 million kilometers) away from the Sun.
    • Seasons and Days: A day on Mars, called a "sol," is about 24.6 hours long, very similar to an Earth day. However, a year on Mars lasts 687 Earth days.
    • Water Ice: Mars has polar ice caps made of water and dry ice (frozen carbon dioxide). There is also evidence that liquid water once flowed on its surface.
    • Largest Volcano: Olympus Mons on Mars is the tallest volcano in the solar system, standing about 13.6 miles (22 kilometers) high.
    • Tallest Mountain: Mars is home to the tallest mountain in the solar system.
    • Dust Storms: Mars experiences the largest dust storms in the solar system, which can cover the entire planet and last for months.
  30. Around 4.5 billion years ago, a Mars-sized object, often referred to as Theia, collided with the early Earth in a cataclysmic impact that ejected vast amounts of debris into space. This material eventually coalesced in Earth's orbit, forming the Moon, which was initially about 16 times closer to Earth than it is today. Over time, due to tidal interactions, the Moon has been gradually drifting away from Earth at a rate of approximately 3.8 centimeters (1.5 inches) per year, a phenomenon confirmed by laser measurements from reflectors placed on the lunar surface during the Apollo missions. This slow recession continues to subtly influence Earth's rotation and the length of our days.
  31. Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, larger only than Mercury. Known as the Red Planet due to its iron-rich surface, Mars is easily visible from Earth with the naked eye, often appearing as a bright reddish "star" in the night sky. The average journey from Earth to Mars takes about 150 to 300 days, depending on the spacecraft's speed and the alignment of the planets. Every 26 months, Mars reaches opposition, its closest point to Earth, which can be as near as 55 million kilometers (34 million miles). These periodic close approaches make Mars a prime target for exploration and observation.
  32. Mars is the planet most commonly associated with an orange color, often referred to as the "Red Planet" due to its rusty-orange appearance caused by iron oxide (rust) in its soil. Jupiter also displays orange hues, particularly in its cloud bands, which are composed of various gases and compounds that produce a mix of colors including orange, white, brown, and red. While Mars has a more uniform surface coloration, Jupiter's orange tones are part of its dynamic and multicolored atmosphere.
  33. Venus may steal the spotlight during its closest approaches to Earth, but Mercury quietly claims the title of our nearest planetary neighbor on average—a revelation that upends conventional wisdom. Due to its rapid orbit and frequent proximity to Earth's path around the Sun, Mercury maintains a mean distance of just 1.04 astronomical units (AU), compared to Venus's 1.14 AU. With one AU measuring roughly 149.6 million kilometers, this subtle shift in perspective reshapes how planetary closeness is truly measured. In the grand choreography of the solar system, Mercury emerges not as a fleeting visitor, but as a steady companion in Earth's cosmic neighborhood.
  34. Venus was the first planet to be explored by a spacecraft, with NASA's Mariner 2 performing the first successful planetary flyby in 1962. It was also the first planet whose surface was reached by a spacecraft from Earth, when the Soviet Venera 7 made a successful soft landing in 1970. Venus has remained a key target in space exploration due to its extreme conditions and Earth-like qualities. More recently, NASA's Parker Solar Probe, although primarily designed to study the Sun, has made multiple flybys of Venus for gravity assists. During its February 2021 flyby, the spacecraft's WISPR instrument captured the first visible light images of Venus's surface from space, revealing glowing features on the planet's nightside through its thick cloud cover. These groundbreaking observations have opened new avenues for understanding Venus's geology and atmospheric composition.
  35. Venus is the second planet from the Sun, orbiting at a distance of approximately 67 million miles (108 million kilometers). Beneath its dense atmosphere lies a rocky surface marked by dome-shaped volcanoes, deep rifts, towering mountains, and vast volcanic plains that stretch across the planet. Venus also features enormous ridged plateaus, hinting at a geologically active past. The planet is permanently cloaked in thick, toxic clouds of sulfuric acid, which begin at altitudes between 28 and 43 miles (45 to 70 kilometers) above the surface. These clouds not only block visible light, making the surface invisible from space, but also emit a pungent odor reminiscent of rotten eggs, thanks to the presence of sulfur compounds—a fitting trait for one of the most hostile environments in the Solar System.
  36. Venus is the hottest planet in the Solar System, with surface temperatures soaring to around 864°F (462°C)—hot enough to melt lead. This extreme heat has made exploration incredibly challenging, with robotic landers surviving only a few hours before succumbing to the harsh conditions. Although Venus is only the second planet from the Sun, its dense atmosphere, composed primarily of carbon dioxide, fuels a runaway greenhouse effect that traps heat with brutal efficiency. In contrast, Mercury, the closest planet to the Sun, remains cooler because it lacks a substantial atmosphere to retain heat. Venus's thick cloud cover and atmospheric pressure—over 90 times that of Earth's—make it a truly hellish world, defying expectations based solely on its distance from the Sun.
  37. Venus is the second planet from the Sun and is Earth's closest planetary neighbor. Venus rotates on its axis backward, compared to most of the other planets in the solar system. This means that, on Venus, the Sun rises in the west and sets in the east, opposite to what we experience on Earth. Venus has a slow axis rotation which takes 243 Earth days to complete its day. The orbit of Venus around the Sun is 225 Earth days, making a year on Venus 18 days less than a day on Venus.
  38. The only planets in our solar system that do not have any moons are Mercury and Venus. These two innermost planets lack natural satellites, likely due to their proximity to the Sun. The Sun's strong gravitational influence makes it difficult for these planets to retain moons; any potential satellites would either crash into the planet or be pulled away by solar gravity. In Mercury's case, its small size and closeness to the Sun make stable moon orbits nearly impossible. Venus, while farther out, may have had a moon in the past, but theories suggest it was lost due to a massive collision that altered the planet's rotation. As of now, Mercury and Venus remain the only moonless planets in the solar system.
  39. A day on Mercury is actually longer than its year due to its extremely slow rotation. Mercury takes about 59 Earth days to complete one full rotation on its axis, while it orbits the Sun in just 88 Earth days. This means that a single solar day—the time from one sunrise to the next—lasts about 176 Earth days on Mercury. Its unique rotational and orbital dynamics create extreme temperature variations and make it one of the most fascinating planets in our solar system.
  40. Jupiter's Great Red Spot is a massive, swirling storm that has raged for centuries, but it is gradually shrinking over time. Once large enough to engulf three Earths, the storm has been steadily contracting since at least the late 1800s and is now only slightly larger than one Earth. Scientists believe the shrinking may be due to a decrease in smaller storms feeding into it, which previously helped sustain its size and energy. Despite its reduced diameter, the storm is growing taller and remains one of the most iconic and powerful features in our solar system.
  41. Jupiter, the largest planet in the solar system, may have up to 600 moons that are 800 meters wide or larger, according to a study by astronomers at the University of British Columbia. By analyzing archival images taken with the Canada-France-Hawaii Telescope, researchers identified 52 potential new moons, 45 of which had not been previously cataloged. These small moons are thought to have irregular and retrograde orbits, meaning they orbit in the opposite direction of Jupiter's rotation. The estimate of 600 moons comes from extrapolating the number of detections in a small portion of the sky around Jupiter to the entire region, suggesting a vast population of tiny, faint satellites yet to be confirmed
  42. Standing on Pluto would be a surreal and precarious experience. The dwarf planet's surface is composed primarily of frozen nitrogen, methane, and carbon monoxide, forming a crust of extremely solid ice mixed with dust and rock. This ice is far colder and more rigid than any naturally occurring ice on Earth, making stable footing difficult. Due to Pluto's low gravity, which is only about 6% that of Earth's, any object or person would feel significantly lighter. Despite its distant, icy allure, Pluto remains a hostile and alien environment, captivating for scientific exploration but utterly inhospitable for human habitation.
  43. Uranus is composed primarily of icy fluids and gases, including water, methane, and ammonia, layered above a small rocky core, making it an ice giant rather than a solid planet like Earth. This composition results in a relatively low density, making Uranus light for its size despite its large volume. The surface gravity on Uranus is about 86% that of Earth's, so an object weighing 200 pounds on Earth would weigh approximately 172 pounds on Uranus, assuming a hypothetical solid surface to stand on. This lower gravity is due to the planet's extended radius and gaseous makeup, contributing to its unique physical characteristics among the outer planets.
  44. Uranus is often referred to as the green planet, though its actual appearance is more of a pale blue-green or turquoise hue. This distinctive coloration is caused by methane gas in its atmosphere, which absorbs the red wavelengths of sunlight and reflects blue and green light back into space. According to NASA Science and The Planetary Society, the presence of methane is the key factor behind Uranus's characteristic color. While the exact shade may vary depending on observational instruments and image processing, the planet's unique tint sets it apart from its neighboring ice giant, Neptune, which appears a deeper blue due to differences in atmospheric composition and cloud structure.
  45. As an ice giant, Uranus is composed mostly of swirling, icy fluids—including water, ammonia, and methane—layered above a small rocky core, with no true ground to walk on. Even if a surface did exist, the planet's extreme conditions would make human survival impossible: temperatures plunge to a frigid -224°C (-371°F), making it the coldest planet in the solar system, and the atmospheric pressure would crush any human-made structure long before reaching the core. According to NASA scientists, Uranus' atmosphere is a dynamic mix of hydrogen, helium, and methane, and recent observations have revealed complex storm systems and cloud layers that deepen the mystery of its internal structure. Despite its inhospitable nature, Uranus remains a fascinating world, offering scientists a unique laboratory to study planetary atmospheres and the evolution of ice giants.
  46. Stars exhibit remarkable peculiarities that reveal the extremes of cosmic physics. Our Sun, for instance, dominates the solar system by accounting for 99.86% of its total mass. A star's temperature determines its color, with cooler stars glowing red and hotter ones appearing blue or white. Among the most exotic stellar objects are neutron stars, whose density is so extreme that a single teaspoon of their material would weigh billions of tons. Even more enigmatic are black holes, which are theorized to emit a faint quantum glow called Hawking radiation. At the other end of the stellar spectrum lies the Pistol Star, one of the most massive and luminous stars known, shining 10 million times brighter than the Sun. These phenomena underscore the incredible diversity and intensity of stellar behavior across the universe.
  47. There are more stars in the observable universe than grains of sand on all the beaches and deserts of Earth—a staggering comparison that highlights the vastness of space. Astronomers estimate that the universe contains over 100 billion galaxies, each with hundreds of billions of stars, totaling around 10²⁴ stars. In contrast, Earth is estimated to have roughly 10²¹ grains of sand. This mind-bending scale reminds us just how immense and awe-inspiring the cosmos truly is, far beyond anything we encounter in everyday life.
  48. Neutron stars are incredibly dense remnants of massive stars that have undergone a supernova explosion. When such a star exhausts its nuclear fuel, its core collapses under gravity, compressing matter to the point where protons and electrons merge into neutrons. The result is a compact object with a mass greater than the Sun but squeezed into a sphere only about 20 kilometers wide. Neutron stars are so dense that a single teaspoon of their material would weigh billions of tons, and they often exhibit extreme magnetic fields and rapid rotation, making them observable as pulsars.
  49. Stars can bend space, and this is a direct consequence of Einstein's general theory of relativity. All objects with mass warp the fabric of space-time, and the more massive the object, the greater the curvature it causes. Even our Sun is massive enough to bend the path of light from distant stars—a phenomenon known as gravitational lensing. This effect was famously confirmed during a solar eclipse in 1919, when starlight passing near the Sun was observed to shift slightly, proving that light follows the curved space-time around massive bodies. While the Sun's bending effect is subtle, more massive stars and black holes can warp space so dramatically that they create strong lensing effects, distorting or even magnifying the light from objects behind them.
  50. The oldest known star in our galaxy is HD 140283, commonly referred to as the Methuselah star, named after the biblical figure known for his long life. It is a metal-poor subgiant located about 190 light-years away in the constellation Libra. Early estimates placed its age at around 14.5 billion years, which appeared to exceed the age of the universe itself—an obvious paradox. However, more precise measurements using data from the Hubble Space Telescope refined its age to approximately 13.7 billion years, aligning it with the current estimated age of the universe (13.8 billion years). This star likely formed shortly after the Big Bang, making it a rare relic from the early universe.
  51. Stars are truly incredible celestial objects that play a crucial role in the universe. Stars are giant balls of hot gas held together by gravity – primarily made of hydrogen with some helium and small amounts of other elements.
    • Life Cycle: Stars have life cycles that can range from a few million to trillions of years; their properties change as they age.
    • Visibility: On a clear, dark night, you can see about 2,000 to 2,500 stars with the naked eye from any given place on Earth.
    • Temperature and Color: The color of a star indicates its temperature; red stars are the coolest while blue stars are the hottest.
    • Star Formation: Stars form in clouds of gas and dust called nebulae; the process begins when these clouds are disturbed, often by a nearby supernova explosion.
    • Mass and Lifespan: The more massive a star, the shorter its lifespan; massive stars may live only tens of millions of years while smaller stars can shine for billions of years.
    • Sun: The Sun, the closest star from Earth, is a middle-aged star at about 4.5 billion years old; it takes about 8.5 minutes for light from the Sun to reach Earth.
    • Star Clusters: Many stars travel through the galaxy in clusters or with companions; however, the Sun moves through the galaxy alone.
    • Historical Observations: The oldest accurately dated star chart appeared in ancient Egyptian astronomy in 1534 BC; Chinese astronomers recorded the first supernova in 185 AD.
    • Distance: The furthest individual star observed is about 100 million light-years away from Earth in the M100 galaxy of the Virgo Cluster.
  52. Stars appear to twinkle due to a phenomenon called scintillation, which occurs when their light passes through Earth's turbulent atmosphere. The atmosphere is composed of layers with varying temperatures and densities, causing the light to refract, bend, and scatter unpredictably as it travels toward our eyes. This results in rapid changes in brightness and position, creating the familiar twinkling effect. Because stars are so far away, they appear as point sources of light, making them especially susceptible to this distortion. In contrast, planets, which appear as tiny disks, are less affected because their light comes from a broader area, averaging out the fluctuations.
  53. There are many stars significantly larger than our Sun, including red supergiants like UY Scuti and Betelgeuse, which have radii hundreds to over a thousand times greater than the Sun's. These colossal stars dwarf our solar companion in sheer size, though not necessarily in mass. Beyond stars, supermassive black holes—such as Sagittarius A* at the center of the Milky Way—possess masses millions to billions of times greater than the Sun. These black holes dominate the gravitational landscape of their host galaxies and represent some of the most massive objects in the universe.
  54. In massive stars, nuclear fusion progresses through increasingly heavier elements—starting with hydrogen into helium, then helium into carbon and oxygen, and eventually up to iron. Each fusion stage occurs in concentric shells around the core, but once iron forms, fusion halts because iron fusion consumes energy rather than releasing it. When a star runs out of fuel, its fate depends on its mass: low-mass stars like the Sun become red giants, shed their outer layers as planetary nebulae, and leave behind white dwarfs; medium-mass stars follow a similar path but may form more massive white dwarfs; high-mass stars, however, undergo core collapse, triggering a supernova that can leave behind a neutron star or black hole. These supernovae scatter heavy elements into space, playing a crucial role in enriching the cosmos and enabling the formation of planets and life.
  55. After millions of years, the immense pressure and temperature in a forming star's core become high enough to initiate nuclear fusion, the process that powers stars. During fusion, hydrogen nuclei are squeezed together to form helium, releasing a tremendous amount of energy in the form of light and heat. This energy creates outward pressure that balances the inward pull of gravity, preventing the star from collapsing further. This delicate balance—known as hydrostatic equilibrium—is what allows a star to shine steadily for billions of years. In stars like the Sun, this fusion primarily occurs through the proton-proton chain reaction, which is the dominant fusion process in stars of similar mass.
  56. The Pistol Star is one of the most massive and luminous stars in our galaxy, with an estimated mass of around 100 times that of the Sun and a radius of approximately 435 solar radii, which translates to about 213 million kilometers (132 million miles)—large enough to extend beyond the orbit of Mars if placed at the center of our solar system. In contrast, the Sun is considered an average-sized star, and the smallest stars, such as red dwarfs, can have masses as low as 8% to 10% of the Sun's mass5. While the Pistol Star is enormous, it is not the largest known star by radius—that title belongs to Stephenson 2-18, which dwarfs even the Pistol Star.
  57. NASA's Parker Solar Probe launched from Florida Sunday, Aug. 12 2018 to begin its journey to the Sun, where it will undertake a landmark mission. The journey will send it skimming through the Sun's atmosphere at a pace of 450,000 mph — fast enough to get from Washington to New York in about a second. It will fly within 4 million miles of the Sun's surface — seven times closer than any spacecraft has gotten before. That heat shield will not only be exposed to sunlight, it must withstand blasts of 2,600 degrees Fahrenheit — while simultaneously maintaining the instruments on the other side at roughly room temperature. Parker Solar Probe will provide new data on solar activity and make critical contributions to our ability to forecast major space-weather events that impact life on Earth.
  58. Determining the absolute youngest star is challenging because star formation is a continuous process, and many stars are still in the early stages of development. Some of the youngest observable stars are found in active star-forming regions such as the Orion Nebula, Cygnus-X, and the Cat's Paw Nebula (NGC 6334), which contains prestellar cores—dense clumps of gas and dust that are just beginning to collapse into stars. One particularly young system is the binary protostar Z Canis Majoris, estimated to be around 1 million years old, making it a cosmic infant compared to stars like our Sun. These regions offer astronomers a glimpse into the earliest phases of stellar evolution, from cold molecular clouds to fully formed stars.
  59. The Milky Way and Andromeda galaxies are on a collision course, expected to begin merging in about 4 billion years—slightly later than the 3.75 billion years some earlier estimates suggested. Andromeda, located approximately 2.5 million light-years away, is hurtling toward the Milky Way at a speed of about 110 kilometers per second, driven by their mutual gravitational attraction. Although the event sounds cataclysmic, the immense distances between individual stars make direct collisions highly unlikely. Instead, the galaxies will gradually blend into a single, massive elliptical galaxy, dramatically transforming the structure of our cosmic neighborhood.
  60. The Milky Way appears as a band of light in the night sky formed from stars and contains between 100 and 400 billion stars and at least 100 billion planets, with the naked eye we can see about 4,000 stars in each hemisphere of the sky. Stars that are discovered today are in general named for where they are in the sky or the person who found them; each star usually has more than one name, there were around 300 stars were named so far.
  61. The Milky Way is a barred spiral galaxy, estimated to be around 13.6 billion years old, making it nearly as ancient as the universe itself. It spans approximately 100,000 light-years in diameter, with a thin disk that contains most of its stars, gas, and dust. However, this disk is not perfectly flat—it is warped, a distortion likely caused by gravitational interactions with nearby satellite galaxies, particularly the Large and Small Magellanic Clouds4. These interactions, combined with the influence of the Milky Way's dark matter halo, create ripples and asymmetries in the galactic structure, offering clues to its dynamic history and evolution.
  62. The Milky Way is not a perfectly flat disk—it is warped and surrounded by a halo of stars and dark matter, a structure that recent studies suggest may be tilted due to past galactic collisions or the influence of a misaligned dark matter halo. Despite its distorted shape, the galaxy continues to form new stars at an average rate of about six to seven per year, though some estimates suggest this number could be higher. Our solar system is located in the Orion Arm, roughly 26,000 light-years from the galactic center, placing Earth about halfway between the core and the outer edge of the Milky Way's disk. This position offers a relatively stable environment, shielded from the intense radiation and gravitational chaos near the center, making it a favorable location for life to flourish.
  63. By approximating the Milky Way Galaxy as a disk with a radius of 50,000 light-years and a thickness of 1,000 light-years, its volume is estimated to be around 6.7 × 10⁵¹ cubic kilometers. The volume of Earth is approximately 1.08 × 10¹² cubic kilometers. Dividing the galaxy's volume by Earth's volume yields roughly 6.7 × 10³⁹, meaning that about 6.7 decillion Earths could fit within the volume of the Milky Way. This calculation is purely geometric and does not reflect the actual number of Earth-like planets, which is estimated to be around 17 billion based on exoplanet surveys.
▷ Miscellaneous
  1. China's Chang'e-6 robotic spacecraft recently brought back lunar soil samples that contained fragments of volcanic rock dating back to 4.2 billion years; the Chang'e-6 probe used a scoop and drill to obtain about 1,935 grams of soil, containing more than 100 basalt fragments. This finding, which is remarkable that a piece of this old rock has assisted scientists in uncovering more about the moon's history, helps solve the mystery of why the moon's far side is so different from its near side, which has more visible volcanic plains.
  2. Russia, through its space agency Roscosmos, continues to operate spacecraft, primarily through its Soyuz missions to the International Space Station (ISS). While Russia's deep space exploration has faced challenges, it has launched numerous satellites and CubeSats for scientific and educational purposes, and maintains a presence in low-Earth orbit with manned missions and satellite deployments.
  3. Voyager 1, launched in 1977, has been exploring the outer reaches of our solar system for decades and is now in interstellar space, having crossed the heliopause—the boundary where the Sun's solar wind and magnetic field no longer dominate. This region marks the transition from the solar system into the vast space between stars, and Voyager 1 is the first human-made object to enter this realm, continuing to send back valuable data about the conditions in interstellar space.
    • Voyager 1 will not last forever, even though it will continue to drift through space indefinitely. Its ability to communicate with Earth will eventually end due to the declining power output of its three radioisotope thermoelectric generators (RTGs), which convert heat from the decay of plutonium-238 into electricity. As the plutonium decays and the thermoelectric components degrade, the spacecraft's available power steadily decreases. By during 2025, Voyager 1 is expected to lose the ability to power its remaining instruments and communication systems. After that, it will become a silent traveler, carrying a golden record as a message to any distant intelligence it may someday encounter. In about 40,000 years, Voyager 1 will be within 1.6 light-years of the star Gliese 445. In about a billion years, it will have traveled to the opposite side of the Milky Way galaxy relative to the Sun.
      • Voyager 1 is powered by three radioisotope thermoelectric generators (RTGs) that convert heat from the radioactive decay of plutonium-238 (Pu-238) into electricity. This fuel does not propel the spacecraft but instead powers its electronics, instruments, and communication systems. Pu-238 has a half-life of about 87.7 years, meaning its energy output gradually declines over time. As the RTGs produce less power, NASA has been shutting down non-essential systems to conserve energy. Eventually—likely by the late 2020s—the remaining power will be insufficient to operate any instruments or transmit signals, and Voyager 1 will become a silent, drifting relic of human exploration.
  4. In addition to Voyager 1, NASA has several other spacecraft still active in space. Voyager 2, launched shortly after Voyager 1 in 1977, is also in interstellar space, traveling in a different direction and continuing to send data back to Earth. Other active NASA missions include the New Horizons probe, which flew by Pluto in 2015 and is now exploring the Kuiper Belt, and the Parker Solar Probe, which is studying the Sun's outer atmosphere.
    • Voyager 2 has been active since 1977 and in contact with Earth, though it is operating on limited power due to the gradual decay of its plutonium-based energy source. To extend the mission's lifespan—potentially into the 2030s—NASA has begun shutting down non-essential systems and some science instruments, including the plasma science instrument, which was turned off in 2024. Despite these reductions, Voyager 2 continues to operate four science instruments and is still sending back valuable data from interstellar space, having crossed the heliopause—the boundary marking the edge of the Sun's influence—in 2018. It remains one of humanity's most distant and enduring explorers.
      • Voyager 2 is fueled by two key sources: hydrazine for attitude control and plutonium-238 for electrical power. At launch, it carried about 100 kilograms (220 pounds) of hydrazine, which is used to operate its thrusters for orientation rather than propulsion. This supply is expected to last until around 2034, although Voyager 2 has used more hydrazine than Voyager 1 due to its extended planetary encounters with Uranus and Neptune. For electricity, Voyager 2 relies on radioisotope thermoelectric generators (RTGs) that convert heat from the decay of plutonium-238 into power. As the plutonium decays, the RTGs produce less energy, gradually limiting the spacecraft's ability to operate instruments and communicate with Earth.
    • Although both Voyager 1 and Voyager 2 traveled beyond the orbit of Pluto, neither spacecraft conducted a close flyby of the dwarf planet. Voyager 1's trajectory was designed to prioritize encounters with Jupiter and Saturn, with a specific focus on a close flyby of Saturn's moon Titan. This encounter altered its path, sending it upward out of the plane of the solar system and making a Pluto flyby impossible. Voyager 2 followed a different trajectory that allowed it to visit Uranus and Neptune, but it too did not pass near Pluto. A dedicated Pluto flyby would later be accomplished by NASA's New Horizons mission in 2015.
  5. The speed of light in a vacuum is an astonishing 299,792,458 meters per second, making it the fastest known phenomenon in the universe. By comparison, sound travels through air at only about 343 meters per second at room temperature. This means light is nearly 874,000 times faster than sound. Moreover, light can move effortlessly through the vacuum of space, while sound depends on a physical medium—such as air, water, or solid materials—to propagate. This fundamental difference explains why we see lightning before we hear thunder and why space is eerily silent despite its cosmic activity.
  6. The sky appears blue due to a phenomenon known as Rayleigh scattering. When sunlight enters Earth's atmosphere, it interacts with air molecules, primarily nitrogen and oxygen, which are much smaller than the wavelength of visible light. These molecules scatter shorter wavelengths—such as blue and violet light—more effectively than longer wavelengths like red or yellow. Although violet light is scattered even more than blue, the sky appears blue because human eyes are more sensitive to blue, and some violet light is absorbed by the upper atmosphere. This scattered blue light reaches observers from all directions, giving the sky its familiar hue on clear days.
  7. Light can travel without air, and this is one of its most fascinating properties. Unlike sound or ocean waves, which require a physical medium like air or water to propagate, light is an electromagnetic wave composed of oscillating electric and magnetic fields. These fields can self-propagate through the vacuum of space, meaning light doesn't need a medium to move. This is why we can see light from distant stars and galaxies, even though it has traveled billions of light-years through empty space. Light also behaves as a particle, called a photon, which carries energy and momentum. This wave-particle duality allows light to move freely in a vacuum at its maximum speed—about 299,792 kilometers per second.
  8. In most regions of space, one hour is practically equivalent to one hour on Earth, because the effects of time dilation—a phenomenon predicted by Einstein's theories of relativity—are usually extremely small. Time dilation occurs due to high velocities (special relativity) or strong gravitational fields (general relativity). For example, astronauts aboard the International Space Station, traveling at about 28,000 km/h, experience time slightly more slowly than people on Earth—aging about 0.007 seconds less over six months. However, these differences are negligible unless one is moving at near-light speeds or near massive objects like black holes, where time can slow dramatically. While time dilation is real and measurable, it has minimal impact on everyday timekeeping in most of space.
  9. In the film Interstellar, Miller's planet is located extremely close to a supermassive black hole named Gargantua, whose immense gravitational field causes severe time dilation—a phenomenon predicted by Einstein's theory of general relativity. As a result, time on the surface of Miller's planet passes much more slowly compared to time experienced farther away, such as by Romilly aboard the Endurance or by people on Earth. Romilly calculated that one hour on Miller's planet would correspond to approximately seven years on Earth, illustrating the dramatic effects of gravitational time dilation near a black hole.


NASA Space Shuttle First Flight # Missions Final Flight
Columbia * April 12, 1981 28 Feb 1, 2003
Challenger * April 4, 1983 10 Jan. 28, 1986
Discovery Aug. 30, 1984 39 Feb 24, 2011
Atlantis October 3, 1985 33 July 8, 2011
Endeavour May 7, 1992 25 May 16, 2011
Spacecraft Builder 1st Launch/Max Crew Length/ Liftoff Mass
Space Shuttle Rockwell Int'l 1981 / 7 122 ft / 240,000 lbs
Soyuz TMA RSC Energia 1966 / 3 24.5 ft / 15,985 lbs
ATV ESA 2008 / 0 35.1 ft /46,000 lbs
SpaceX Dragon SpaceX 2010 / 7 20.4 ft / 26,460 lbs
NASA MPCV Lockheed Martin Unknown / 4 26 ft / 46,848 lbs


Space News, Info & Facts
▷ Space & Astronomy Discussion Forum
Discussion Forum .

▷ Space News, Info & Facts
  1. A Comprehensive Comparison of Heat Shields: Mercury, Gemini, Apollo, Space Shuttle, Orion, Starliner, Dragon Crew, Dream Chaser, X-37, Starship, and International Spacecraft from China, Russia, and India
  2. Supersonic Flight
  3. Pictures from Space
  4. Space Exploration
  5. Space Science-Astronomy and Space Physics
  6. Space Based Astronomy
  7. Space and Astronomy
  8. Astronomy and Space Science: Space Exploration
  9. Astronomy and Space Science: The Telescope
  10. Space Telescope
  11. The Space Shuttle.
  12. The Space Shuttle at Work.
  13. International Space Station | NASA
  14. Life in the Universe: What Are the Odds?
  15. Scientist Calculates Odds Alien Life Is Common in the Universe
  16. The Best Evidence for Life Elsewhere in the Universe
  17. Will Humans Be Living in Space in the Next 50 Years?
  18. Eating in Space | NASA
  19. Amazing Space
  20. Can People Live in Space?
  21. Astronomy & Space: Tour the Cosmos and Beyond
  22. Astrophysics and Space Science
  23. A Little Astrophysics - From the Big Bang to Now - Big Bang Model
  24. Signs of Alien Life Will Be Found by 2025, NASA's Chief Scientist Predicts
  25. My Place in Space
  26. Do You Have What It Takes to Survive in Space?
  27. Space and Survival
  28. Challenges Security Space: Space Reliance in an Era of Competition and Expansion
  29. Taking Flight on Another World - Mars Helicopter
  30. NASA Television
  31. NASA's UFO Report
  32. NASA - Living in Space
  33. NASA's Voyager Will Do More Science With New Power Strategy
  34. NASA Hears 'Heartbeat' From Voyager 2 After Inadvertant Blackout
  35. NASA Listens for Voyager 2 Spacecraft After Wrong Command Cuts Contact
  36. NASA's Voyager 2 Probe 'Leaves the Solar System'
  37. NASA's Voyager 2 Probe Enters Interstellar Space
  38. NASA Solar System Exploration: In Depth - Voyager 2
  39. NASA Finally Makes Contact With Voyager 2 After Longest Radio Silence in 30 Years
  40. NASA's InSight ‘Hears' Its First Meteoroid Impacts on Mars
  41. NASA Has Captured ‘Actual Sound' in Space and It's Honestly Terrifying
  42. NASA Finds Mars Meteor Impacts Left Craters and Shook Planet
  43. NASA's James Webb Space Telescope Launch: Live updates
  44. NASA's James Webb Space Telescope Rolls out for Christmas Launch (12/2021)
  45. NASA Satellites Make Magnetic Discovery in Turbulent Space Near Earth
  46. Webb Telescope to Take Unprecedented Look at Exoplanets
  47. The James Webb Telescope Is Built for Infrared 'First Light'
  48. James Webb Space Telescope | NASA
  49. James Webb Space Telescope Info | NASA
  50. Voyager 2
  51. Voyager 1 and 2: The Interstellar Mission
  52. America's Most Expensive Fighter Jet Totaled in First-Ever Crash
  53. On the Definition and Legal Status of Spacecraft (1963)
  54. The Theory of Interstellar Trade | Princeton University
  55. There May Be Life on Mars, But This NASA Report Doesn't Prove It
  56. Samples from Far Side of the Moon Show History of Ancient Volcanoes
  57. Lunar Samples Record Impact 4.2 Billion Years Ago that ...
  58. Luftwaffe Pictures, Video, Facts & News
  59. Comparison of Space Station Cargo Vehicles
  60. X-37B Orbital Test Vehicle
  61. X-40 Space Maneuver Vehicle
  62. Space Shuttle Avionics System.
  63. Automated Transfer Vehicle (Spacecraft) (Europe)
  64. Progress 7K-TG (Spacecraft) (Russia)
  65. TKS (Spacecraft) (Russia)
  66. Progress-M & Progress-M1 (Spacecraft) (Russia)
  67. Flight Research at Ames, 1940-1997.
  68. Unmanned Space Project Management: Surveyor and Lunar Orbiter.
  69. The Planetary Quarantine Program.
  70. Constellation Program Lessons Learned Volume 1: Executive Summary.
  71. Quest for Performance: The Evolution of Modern Aircraft.
  72. The Long Duration Exposure Facility (LDEF): Mission 1 Experiments.
  73. Voyager 1 and 2, Atlas of Saturnian Satellites.
  74. Far Travelers: The Exploring Machines.
  75. Congress Heard More Testimony About UFOs
  76. Pentagon Received Hundreds of Reports of New UFO Sightings
  77. Are UFOs a Threat to National Security?
  78. Spacecraft Brings Russians, American Back to Earth
  79. Shenzhou (Spacecraft) | Wikipedia
  80. China-Russia Space Cooperation: The Strategic, Military, Diplomatic, and Economic Implications of a Growing Relationship
  81. China's First Astronaut Revealed
  82. Armstrong Fact Sheets | NASA
  83. 'Starship in Space': See Amazing Photos from SpaceX Starship's Flight 9 Test Mission
  84. SpaceX's Starship Spacecraft Lost After Flight 8 Launch
  85. SpaceX Starship: Smooth Launch But Spacecraft Makes Uncontrolled Re-entry
  86. SpaceX's Ninth Starship Test Flight Delivers Mixed Results
  87. SpaceX Starship (video)
  88. Starship: SpaceX's fully-reusable Mars rocket
  89. SpaceX | BBC News
  90. SpaceX Launch
  91. SpaceX Launches Its Most Ambitious Starship Test Flight Yet.
  92. SpaceX Launches Mega Rocket, Lands All Three Boosters
  93. SpaceX Launches a Record 143 Satellites on One Rocket, Aces Landing
  94. SpaceX Catches Giant Starship Booster With 'Chopsticks' on Historic Flight 5 Rocket Launch and Landing
  95. SpaceX Catches Starship Rocket Booster for First Time Ever as It Returns to Earth After Launch
  96. SpaceX's Dragon (Spacecraft) (US) - SpaceX CSR2 Mission
  97. SpaceX Returns 4 Astronauts to Earth; Rare Night Splashdown (5/2/2021)
  98. Crew Dragon Brings Four Astronauts Back to Nighttime Splashdown
  99. In Seven Years, SpaceX Could Land Humans on Mars?
  100. Orbital Sciences Corp's Cygnus (Spacecraft) (US)
  101. Lockheed Martin's Orion (Spacecraft) (US)
  102. Sierra Nevada Corporation (SNC)'s Dream Chaser (Spacecraft) (US)
  103. Cassini Saturn Probe Gets 7-Year Life Extension
  104. Spaceborne Digital Computer Systems.
  105. Satellite - Satellite Basics
  106. Communications Satellite
  107. Overview of Satellite Communications
  108. Satellite Frequency Bands | ESA
  109. An Introduction to 25-328.6 MHz Band
  110. ITU Regulations for Ka-band Satellite Networks
  111. 10 Things Learned About UFOs and Aliens in 2022
  112. 11 Pros and Cons of Space Exploration
  113. 12 Greatest Challenges for Space Exploration
  114. 20 Inventions We Wouldn't Have Without Space Travel
▷ How, Who, What, When, Where, Which & Why
  1. How to Design a Spaceship
  2. How to Land the Space Shuttle... from Space (video)
  3. How to Survive a Year in Space
  4. How to Survive in Space
  5. How to Survive in Space | The Royal Institution
  6. How to Survive in Space | NASA
  7. How to Survive in Space | ESA
  8. How to Survive Living in Space (video)
  9. How to Survive Pandemic Reentry
  10. How Did the Big Bang Happen?
  11. How the Big Bang Theory Works
  12. How Humans Survive in Space?
  13. How Astronomers Decided Where to Point NASA's James Webb Space Telescope
  14. How Ancient Astronomy Mixed Science with Mythology
  15. How Can You Sign up to Send Your Name on the Next Mars Mission?
  16. How Old Is the Universe?
  17. How Long Can a Human Survive in Outer Space?
  18. How Big is Our Universe? | NASA
  19. How Big Is Our Universe? An Exploration through Space and Time | Harvard
  20. How the Universe Is Way Bigger Than You Think | YouTube
  21. How Extremophilic Bacteria Survive in Space for One Year
  22. How Many Types of Galaxy Are There?
  23. How Many Earths Can Fit in the Sun?
  24. How Do You Stay Alive in Space?
  25. How Does Future Planet Count Carbon?
  26. How Rockets Are Made (video)
  27. How Andrei Linde Redefined the Universe
  28. How the Universe Works
  29. How Can Astronomy Improve Life on Earth? | Harvard
  30. How Much Does a Full NASA Space Suit Cost?
  31. What Are the Oldest Objects in the Universe? Ancient Stars, Planets, and Galaxies Explained
  32. What Is a Satellite? | NASA
  33. What Is the James Webb Space Telescope? | NASA
  34. What Is the Hubble Space Telescope? | NASA
  35. What Is the Fermi Gamma-ray Space Telescope? | NASA
  36. What Is Robonaut? | NASA
  37. What Is Robotics? | NASA
  38. What Is Astronomy?
  39. What Is the Big Bang Theory?
  40. 'What Is That?' Navy Pilots Report Unexplained Flying Objects
  41. What Is Space? - A Definition of Our Universe and Beyond
  42. What Is the Probability of Life in Universe?
  43. What Is the Statistical Probability of Life on other Planets?
  44. What Is a Subsurface Ocean & Could It Support Life?
  45. What Is the Difference Among Solar System, Galaxy, Universe?
  46. What Do Sunrises and Sunsets Look Like on Mars?
  47. What Does It Take for a Robot to Survive in Space
  48. What Does It Take to Survive in Space?
  49. What Will Astronauts Need to Survive the Dangerous Journey to Mars?
  50. What Kind of Universe Exists?
  51. What Supplies Do You Need to Survive in Space?
  52. What Materials Can Survive in Space?
  53. What Made Apollo a Success?
  54. What Happens When a Star Dies?
  55. What Happened Before the Big Bang
  56. What Really Happened at Our Universe's Birth? - Big Bang
  57. What Future Holds for Astronomy, Astrophysics, and Space Science
  58. Who Are the Black Astronomers and Astrophysicists?
  59. Who Is the Most Famous Cosmonaut?
  60. Who Discovered that the Sun Was a Star?
  61. Why It's Tough to Survive a Year in Space
  62. Why Man Explores.
  63. Why Go to Mars?
  64. Why Is Astronomy Important?
  65. Why We Will Never Know Everything About Our Universe
  66. Why Complex Life Is Uncommon in the Universe - Rare Earth
  67. Why Do Sunsets On Mars Look Blue?
▷ History, Guides & Tips
  1. Astronomy | Wikipedia
  2. Astronomy: Definition, History, Discoveries, & Facts
  3. The History of Astronomy | Cornell
  4. History of Astronomy | uoregon.edu
  5. History of Astronomy | Britannica
  6. History of Astronomy
  7. History of Astronomy | Wikipedia
  8. History of Astronomy in China
  9. Astronomy in History
  10. A History of Astronomy
  11. A Brief History of Astronomy
  12. A Brief History of the Astronomy Basics - Its Origins & Celestial Motions
  13. A Short History of Geophysical Radar at Arecibo Observatory
  14. A History of Astronomy, Astrophysics and Cosmology
  15. A History of Astrometry Part I: Mapping the Sky from Ancient to Pre-modern Times
  16. Emblems of Exploration - Monographs in Aerospace History
  17. Space Artifacts: Are They Historical Evidence?
  18. SpaceX Poised to Launch Cargo from Historic NASA Pad.
  19. SpaceX, NASA Hail 1st Falcon 9 Rocket Launch from Pad Steeped in History.
  20. Critical Issues in the History of Spaceflight
  21. Cosmic Journey: A History of Scientific Cosmology
  22. NASA History: Innovation at 100
  23. NASA's First 50 Years: Historical Perspectives.
  24. The High Speed Frontier: Case Histories of Four NACA Programs, 1920-1950.
  25. Orders of Magnitude: A History of the NACA and NASA, 1915-1990.
  26. Making the Invisible Visible: A History of the Spitzer Infrared Telescope Facility (1971–2003)
  27. Toward a History of the Space Shuttle: An Annotated Bibliography Part 2, 1992–2011.
  28. History of Research in Space Biology and Biodynamics at the Air Force Missile Development Center, Holloman Air Force Base, New Mexico, 1946-1958.
  29. Elegance in Flight: A Comprehensive History of the F-16XL Experimental Prototype and Its Role in NASA Flight Research
  30. Historical Studies in the Societal Impact of Spaceflight
  31. Ideas Into Hardware: A History of the Rocket Engine Test Facility at the NASA Glenn Research Center.
  32. Wisconsin at the Frontiers of Astronomy: A History of Innovation and Exploration
  33. Present and Future State of the Art in Guidance Computer Memories.
  34. A New Universe to Discover - A Guide to Careers in Astronomy
  35. Researcher's Guide to International Space Station:
  36. SpaceX Starship Users' Guide
  37. Launch: Payload User's Guide.
  38. Researcher's Guide to International Space Station:
  39. On the Moon with Apollo 16: A Guide to the Descartes Region.
  40. Skylab: A Guidebook.
  41. Guide to Magellan Image Interpretation.
  42. Guide to Planets, Stars and Galaxies
  43. Navigating the Stars: A Young Learner's Guide to Astronomy
  44. Astronomy for Kids: A Comprehensive Guide to Explore the Wonders of Outer Space from Home
  45. Beginner's Guide to Aerodynamics
  46. Beginner's Guide to Compressible Aerodynamics
  47. Beginner's Guide to Wind Tunnels
  48. NASA Beginner's Guide to Propulsion
  49. An Astronaut's Tips for Living in Close Quarters | NASA
  50. 5 Tips NASA Astronauts Use When Living in ‘Confinement' in Space to Stay Happy and Productive
  51. 15 Space Travel Tips from an Astronaut


Astronomy, Universe, Info & Facts
  1. Astronomy Timeline
  2. Astronomy
  3. Astronomy 101
  4. Astronomy 101: The Basics of Learning Astronomy
  5. Astronomy & Astrophysics 101: Big Bang
  6. Astronomy Basics
  7. Astronomy Facts
  8. Astronomy | Crash Course
  9. Astronomy FAQs
  10. Astronomy for Beginners
  11. Astronomy: The Study of the Universe
  12. Astronomy in Everyday Life
  13. Astronomy: Everything You Need to Know | Space
  14. Astronomy and Astrophysics in the New Millennium
  15. Astronomy Education Research: Developmental History of the Field and Summary of the Literature
  16. Astronomy Books List
  17. Astronomy Books Online
  18. Astronomy 801: Planets, Stars, Galaxies, and the Universe
  19. Astronomical Events — Astronomy Calendar
  20. Astronomical Myths in India
  21. Astrophysicists Discover that Ultrahot Planets Have Starlike Atmospheres
  22. The Astronomy of the Age of Geometric Altars
  23. Astronomers Discover Rare Distant Object in Sync with Neptune
  24. Astronomers Discover Monster Exoplanet Hiding in 'Stellar Fog' Around Young Star
  25. Astronomers Discover Gliese 12 b, a Potentially Habitable Exoplanet
  26. Astronomers Discover a Planet that's Rapidly Disintegrating, Producing a Comet-like Tail
  27. Babylonian Astronomy
  28. General Astronomy
  29. Impact of Astronomy
  30. An Overview of Astronomy
  31. An Overview of New Worlds, New Horizons in Astronomy and Astrophysics
  32. Big Ideas in Astronomy
  33. Introduction to Cosmology
  34. Introduction to the Universe
  35. Introduction to Astronomy
  36. Introduction to Astronomy and Cosmology
  37. Introduction to Astronomy from Darkness to Blazing Glory
  38. Introduction to Solar System Astronomy
  39. An Introduction to the Sun
  40. An Introduction to Moons, Planets, Solar System, Stars, Galaxies, in our Universe
  41. Cosmology FAQ
  42. Cosmology: Discoveries and Mysteries
  43. Cosmology and 21st-Century Culture
  44. Cosmology and Astronomy | Khan Academy
  45. NASA Just Got a Rare Look Inside Uranus
  46. NASA Planet Hunter Finds Its 1st Earth-Size Habitable-Zone World
  47. NASA Satellite Discovers Second Earth-Sized Planet in Habitable Zone
  48. NASA Gets Unusually Close Glimpse of Black Hole Snacking on Star
  49. NASA Helps Decipher How Some Distant Planets Have Clouds of Sand
  50. NASA Confirms Evidence That Liquid Water Flows on Today's Mars
  51. NASA to Reveal New Video, Images from Mars Perseverance Rover
  52. NASA's Mars Perseverance Rover Provides Front-Row Seat to Landing, First Audio Recording of Red Planet
  53. NASA's Spitzer Confirms Closest Rocky Exoplanet
  54. NASA's Hubble Shows Milky Way Is Destined for Head-On Collision
  55. NASA's Spitzer Space Telescope Ends 16-Year Mission of Discovery
  56. NASA's Perseverance Rover Gives High-Definition Panoramic View of Landing Site
  57. Baby Star 'Burps' Tell Tales of Frantic Feeding, NASA Data Shows
  58. Amazing Space
  59. New 'Baby Picture' of Universe Unveiled
  60. The Tidal Disruption Event AT2021ehb: Evidence of Relativistic Disk Reflection, and Rapid Evolution of the Disk–Corona System
  61. In Depth | Spitzer Space Telescope | NASA Solar System Exploration
  62. Spitzer Space Telescope Images
  63. Spitzer Space Telescope
  64. Spitzer Space Telescope | Wikipedia
  65. Spitzer Space Telescope | Harvard Center for Astrophysics
  66. A Terrestrial Planet Candidate in a Temperate Orbit Around Proxima Centauri
  67. Age of the Universe
  68. Age of the Universe | Wikipedia
  69. New Research Puts Age of Universe at 26.7 billion Years, Nearly Twice as Old as Previously Believed
  70. The Universe Could be 26.7 Billion Years Old, Twice as Old as Current Estimates
  71. Is the Universe Twice as Old as We Thought?
  72. Physical Cosmology and an Exoplanet Orbiting a Solar-Type Star
  73. "In a Beginning..." Quantum Cosmology and Kabbalah
  74. The Road to Precision Cosmology
  75. Visions of Discovery: New Light on Physics, Cosmology, and Consciousness
  76. "The Most Philosophically of All The Sciences": Karl Popper and Physical Cosmology
  77. Our Cosmic Origins
  78. The Start of Scientific Cosmology
  79. The Most Famous Cosmonauts
  80. Famous Astronauts and Cosmonauts
  81. List of Cosmonauts
  82. Life, the Universe, and Everything
  83. From Cosmic Birth to Living Earth
  84. Big Bang | Wikipedia
  85. Stars, Galaxies, and the Universe
  86. The Hidden Lives of Galaxies
  87. Galaxies Through Space and Time
  88. Galaxies Facts and Information
  89. Galaxies in the Local Universe
  90. Galaxies in the Universe
  91. Galaxies and the Milky Way
  92. Galaxies in the Universe: An Introduction
  93. Galaxies Galore
  94. Galaxies | Astronomy
  95. Galaxies | HubbleSite
  96. Stars and Galaxies
  97. Stars, Planets, and Galaxies
  98. Pistol Star, One of our Galaxy's Brightest Stars
  99. The Pistol Star: A Brilliant Star in Milky Way's Core
  100. Milky Way Galaxy: Size, Definition, & Facts
  101. Milky Way Galaxy: Facts About Our Cosmic Neighborhood
  102. Andromeda – Milky Way Collision
  103. The Andromeda and Milky Way Collision, Explained
  104. Connecting the Physics of Stars, Galaxies and the Universe
  105. The Differences Between a Universe, Galaxy & Solar System
  106. The Mysterious Universe (Book)
  107. The Study of the Universe
  108. Fossil Galaxy Discovered Three Billion Light-Years Away
  109. James Jeans and the Mysterious Universe
  110. Formation of the Universe and our Solar System
  111. Beyond Earth
  112. Beyond Earth: A Chronicle of Deep Space Exploration
  113. The Earth in the Solar System
  114. Earth and Space Science – Planets & Stars
  115. The Moon Is Shrinking, Causing Moonquakes at a Potential NASA Landing Site, Study Finds
  116. Shrinking Moon Causing Moonquakes and Faults Near Lunar South Pole
  117. The Moon Is Shrinking—and It Could Affect Future NASA Missions
  118. Solar System, Galaxy and the Universe
  119. Solar System vs. Galaxy vs. Universe
  120. Solar System Scope
  121. Solar System Astronomy Notes
  122. Solar System, Galaxy, Universe: What's the Difference?
  123. Solar Mass
  124. Our Solar System & Earth
  125. Our Solar System: Planets
  126. The Solar System and Beyond
  127. The Solar System and Its Planets
  128. The Origin of the Solar System
  129. The Origin of the Universe
  130. Indigenous Astronomy and the Solar System
  131. Features of Our Solar System
  132. Can You Fit All the Planets Between the Earth and Moon?
  133. Scale of Space: Can You Fit All the Planets Between the Earth and Moon?
  134. You Could Fit All the Planets Between the Earth and the Moon
  135. Planet Earth: An Introduction to Earth Sciences
  136. Planet Found in Habitable Zone Around Nearest Star
  137. Planetary Geology in the 1980s.
  138. Planetary Size and Distance Comparison
  139. Jupiter Now Has a Whopping 79 Moons
  140. Jupiter's Great Red Spot Is Shrinking! But Why?
  141. Jupiter's Great Red Spot Getting Taller as It Shrinks, NASA Team Finds
  142. Hubble Shows that Jupiter's Great Red Spot Is Smaller than Ever Seen Before
  143. Study Helps Solve Mystery Under Jupiter's Coloured Bands
  144. Most Distant Radio Galaxy Ever Discovered
  145. Juno to Remain in Current Orbit at Jupiter
  146. Saturn Moon Riddled with Gushing Geysers, New Images Reveal
  147. Saturn's Icy Moon Enceladus, a Possible Home for Life, Shines in Photo
  148. Enceladus: Saturn's Tiny, Shiny Moon
  149. The Footprints in the Moon Will Last Millions of Years
  150. Are Astronaut Footprints Disappearing from the Moon?
  151. Icy Saturn Moon Pumps Out 15.8 Gigawatts of Heat Power
  152. Space Probe to Plunge into Fiery Corona of the Sun
  153. Looking for Life on a Flat Earth
  154. Black Holes in String Theory
  155. On Brink of Collapse, Famed Puerto Rico Space Telescope (Arecibo Observatory) to Close Down
  156. Genesis of the 1000-foot Arecibo Dish
  157. Testing Proves Its Worth With Successful Mars Parachute Deployment
  158. Science Advice to NASA: Conflict, Consensus, Partnership, Leadership
  159. The Universe
  160. The Universe Through the Eyes of Hubble
  161. The Universe: Size, Shape, and Fate
  162. Universe Facts
  163. Universe at Your Fingertips: An Astronomy Activity and Resource Notebook.
  164. Evolution of the Solar System.
  165. The Evolution of the Universe
  166. Observing the Origin of the Universe
  167. Understanding Our Universe
  168. Secrets of the Universe
  169. Mysteries of the Universe
  170. The Mystery of How Big Our Universe Really Is
  171. Unraveling the Secrets of the Universe
  172. An Expanded View of the Universe
  173. Formation of the Universe and our Solar System
  174. Measuring the Size of the Universe: Galaxy Distance ...
  175. The Future of Universe, Sun, Earth and Humanity
  176. Taking the Measure of the Universe
  177. The Origins of the Universe Facts and Information
  178. Origin and Structure of the Universe
  179. Origin and Evolution of the Universe
  180. Structure and Evolution of the Universe
  181. Unlocking the Secrets of the Universe
  182. Our Place in the Universe
  183. Our Place in the Universe | UCSD
  184. Our Place in Our Galaxy
  185. The Earth and the Universe
  186. From Earth to the Universe
  187. Fun Facts About Our Universe
  188. Highlights of Hubble's Exploration of the Universe
  189. Difference Between Space and Universe
  190. Pre-Big Bang, Space-time Structure, Asymptotic Universe
  191. A Visual Journey Through the Wonders of the Universe
  192. Physics in the Real Universe: Time and Spacetime
  193. The London Science Museum, Cosmonauts, and Russians Making History
  194. Extragalactic Astronomy and Cosmology: An Introduction
  195. Ancient Greek Astronomy and Cosmology
  196. Webb Discovers Methane, Carbon Dioxide in Atmosphere of K2-18 b
  197. TOI-715 b | Wikipedia
  198. Stonehenge and Ancient Astronomy
  199. Modern Astronomy: An Introduction to Astronomy
  200. Curated Community Resources for OpenStax Astronomy
  201. The Golden Book of Astronomy - A Comprehensive and Practical Surveys
  202. Project Gutenberg's An Introduction to Astronomy
  203. The Study of Stars, Galaxies, Planets, and more
  204. Everything We Know About The Planet Made Of Diamonds
  205. Super-Earth Planet Likely Made of Diamond
  206. In Depth - Earth
  207. Earth Facts: Surface, Atmosphere, Satellites, History & Definition
  208. Encyclopedia of Astrophysics
  209. Sources of Misconceptions in Astronomy
  210. Vera Rubin, Astronomer Extraordinaire
  211. Extraterrestrial Liquid Water
  212. Subsurface Oceans on Alien Worlds Even Better for Life than Earth's Oceans?
  213. Nicolaus Copernicus: Father of Modern Astronomy
  214. Online Astronomy Books
  215. Core List of Astronomy Books
  216. 3 Potentially Habitable Worlds Found Around Nearby Ultracool Dwarf Star
  217. 3 Tiny New Moons Found around Uranus and Neptune — and One Is Exceptionally Tiny
  218. 7 Surprising Things About the Universe
  219. 8 Ingredients for Life in Space
  220. 9 of the Most Mind-blowing Facts About the Universe
  221. 10 Things: Spitzer Space Telescope
  222. 10 Top Cosmological Discoveries
  223. 10 Top Mysteries of Outer Space
  224. 10 Top Mysteries of the Universe.
  225. 10 Greatest Soviet Cosmonauts in History
  226. 10 Amazing Facts About Our Universe
  227. 10 Fascinating Facts About the Moon
  228. 10 Interesting Facts About the Milky Way
  229. 10 Wonders of the Solar System
  230. 13 Most Fascinating Astronomy Major Facts
  231. 14 of the Most Baffling Mysteries About the Universe
  232. 15 Unbelievable Facts About the Milky Way
  233. 15 of Spitzer's Greatest Discoveries from 15 Years in Space
  234. 15 Common Astronomy Myths
  235. 15 Top Astronomy Myths
  236. 16 Astounding Facts About Galaxies that Will Boggle Your Brain!
  237. 17 Things You Probably Didn't Know About Our Universe
  238. 20 Extraordinary and Inspiring Facts About the Universe
  239. 25 Imposing Photos of Places on Earth Taken from Space
  240. 40 Interesting Facts About the Milky Way Galaxy
  241. 50 Years of Solar System Exploration
  242. 50 Interesting Facts About Earth
  243. 80 Interesting Facts About the Moon
  244. 92 Interesting Facts About Earth
  245. 100 Facts About Earth
  246. 100 Images of Cosmology, Exoplanets, and Galaxies
  247. 300th Delta Rocket Launches New Window on Universe

Universe & Space Exploration

  1. Video: Universe & Space Exploration
  2. Hubble: An Overview of the Space Telescope
  3. Hubble 25: A Quarter-Century of Discovery with the Hubble Space Telescope
  4. Hubble Focus: The Lives of Stars
  5. Not Yet Imagined: A Study of Hubble Space Telescope Operations
  6. The Mysterious Origins of Universe's Biggest Black Holes
  7. Origins of 21st-Century Space Travel
  8. Walking to Olympus: An EVA Chronology, 1997–2011 Volume 2
  9. Earth and Space Science – The Structure of the Cosmos
  10. Beyond Tube-and-Wing: The X-48 Blended Wing-Body and NASA's Quest to Reshape Future Transport Aircraft
  11. Promise Denied: NASA's X-34 and the Quest for Cheap, Reusable Access to Space
  12. Exploring The Unknown:
  13. The Wind and Beyond:
  14. Remembering the Space Age:
  15. Societal Impact of Spaceflight:
  16. Rockets and People
  17. America's Deep Space Pioneer:
  18. Psychology of Space Exploration.
  19. Cosmos & Culture: Cultural Evolution in a Cosmic Context.
  20. Unmanned Space Project Management: Surveyor and Lunar Orbiter.
  21. X-15 Research Results.
  22. X-15 Research Results With a Selected Bibliography.
  23. Analysis Methods for Multi-Spacecraft Data
  24. Rockets and Launch Vehicles
  25. From Spaceship Earth to Google Ocean: Planetary Icons, Indexes, and Infrastructures
  26. Design, Analysis, and Test of a High-Powered Model Rocket
  27. List of Missions to the Moon.
  28. Shuttle Atlantis STS-132 - Amazing Shuttle Launch Experience
  29. SciShow Space
  30. Shuttle's Boosters Recovered
  31. Space Shuttle Discovery Landing (STS-131)
  32. Unlimited Horizons: Design and Development of the U-2
  33. Parker Solar Probe and the Birth of the Solar Wind
  34. Launches and Orbital Operations - Launches to Orbit and Beyond (2013)
  35. The Power for Flight: NASA's Contributions to Aircraft Propulsion
  36. NASA: Astronauts Return to Earth from Space (8/2/2020)
  37. NASA: A Chronology of Deep Space and Planetary Probes 1958-2000.
  38. NASA: The Space Shuttle and Its Operations
  39. NASA Television
  40. NASA Launches Parker Solar Probe Mission to Study the Sun up Close
  41. NASA Apollo Spacecraft
  42. NASA Langley Aircraft Photo Collection
  43. NASA Spacecraft Rockets Toward Sun for Closest Look Yet
  44. NASA Created a Rare, Exotic State of Matter in Space
  45. NASA's Solar Probe Blasts Off to the Sun
  46. NASA's Planet-Hunter Caught Stunning Video of a Distant Comet
  47. NASA's Parker Solar Probe Launches on a Mission to Study the Sun and its Dangers
  48. Life in the Universe: Proceedings of a Conference Held at NASA Ames Research Center Moffet Field, California, June 19-20, 1979.
  49. Proceedings of the X-15 First Flight 30th Anniversary Celebration of June 8, 1989.
  50. Computers in Spaceflight: The NASA Experience.
  51. Spacelab: An International Short-Stay Orbiting Laboratory.
  52. A Meeting with the Universe: Science Discoveries from the Space Program.
  53. Science in Orbit: The Shuttle & Spacelab Experience: 1981-1986.
  54. Results of the Second Manned Suborbital Space Flight, July 21, 1961.
  55. Results of the Second U.S. Manned Orbital Space Flight.
  56. Results of the Third U.S. Manned Orbital Space Flight.
  57. Mercury Project Summary Including Results of the Fourth Manned Orbital Flight
  58. Exploring Space with a Camera.
  59. Aerospace Food Technology.
  60. Pioneer Odyssey.
  61. Apollo Expeditions to the Moon.
  62. Apollo Over the Moon: A View From Orbit.
  63. Apollo 13 "Houston, we've got a problem."
  64. The Apollo Program Summary Report.
  65. Introduction to the Aerodynamics of Flight.
  66. Biomedical Results of Apollo.
  67. Skylab EREP Investigations Summary.
  68. Skylab: Our First Space Station.
  69. Skylab, Classroom in Space.
  70. Skylab's Astronomy and Space Sciences.
  71. A New Sun: Solar Results from Skylab.
  72. The Search for Extraterrestrial Intelligence.
  73. Atlas of Mercury.
  74. The Voyage of Mariner 10: Mission to Venus and Mercury.
  75. The Martian Landscape.
  76. Project Orion: A Design Study of a System for Detecting Extrasolar Planets.
  77. Wind Tunnels of NASA.
  78. Viking Orbiter Views of Mars.
  79. The Star Splitters: The High Energy Astronomy Observatories.
  80. Planetary Geology in the 1980s.
  81. Quest for Performance: The Evolution of Modern Aircraft.
  82. The Long Duration Exposure Facility (LDEF): Mission 1 Experiments.
  83. Voyager 1 and 2, Atlas of Saturnian Satellites.
  84. Far Travelers: The Exploring Machines.
  85. The Impact of Science on Society.
  86. Living Aloft:  Human Requirements for Extended Spaceflight.
  87. Dynamics of Flight | NASA
  88. Aerodynamics of Flight | FAA
  89. Flight Research at Ames, 1940-1997.
  90. Unmanned Space Project Management: Surveyor and Lunar Orbiter.
  91. The Planetary Quarantine Program.
  92. Constellation Program Lessons Learned Volume 1: Executive Summary.
  93. Spaceborne Digital Computer Systems.
    94. Celebrating a Century of Flight.Wings in Orbit: Scientific and Engineering Legacies of the Space Shuttle.
  94. Report of the Apollo 13 Review Board.
  95. Report of the Presidential Commission on the Space Shuttle Challenger Accident, June 1986 and Implementations of the Recommendations, June 1987.
  96. Transiting from Air to Space: The North American X-15.
  97. Emblems of Exploration: Logos of the NACA and NASA
  98. The First Century of Flight: NACA/NASA Contributions to Aeronautics.
  99. Probing the Sky: Selected NACA Research Airplanes and Their Contributions to Flight
  100. Space Station Requirements and Transportation Options for Lunar Outpost.
  101. Space Station Freedom Accommodation of the Human Exploration Initiative.
  102. Space Handbook: Astronautics and its Applications.
  103. Space Shuttle Avionics System.
  104. The Space Shuttle at Work.
  105. The Space Shuttle.
  106. The Story of Self-Repairing Flight Control Systems.
  107. Magellan: The Unveiling of Venus.
  108. Saturn Illustrated Chronology.
  109. See How It Flies
  110. Introduction to the Aerodynamics of Flight.
  111. Aerodynamics Q&A
  112. UIUC Airfoil Data
  113. FoilSim III
  114. Aircraft Design: Synthesis and Analysis
  115. Modeling Flight
  116. Unmanned Aerial Vehicles
  117. The Eight Planets in Our Solar System
  118. The 5 Dwarf Planets
  119. Other Objects in the Solar System
  120. Wide Field Infrared Survey Telescope: A planned wide field infrared space telescope by NASA.
  121. Space Mega-Projects



Spaceflight
Research & Development
  1. Video: Research & Development
  2. Unlimited Horizons: Design and Development of the U-2
  3. Elegance in Flight: A comprehensive History of the F-16XL Experimental Prototype and its Role in NASA Flight Research
  4. The Power for Flight: NASA's Contributions to Aircraft Propulsion
  5. Parker Solar Probe and the Birth of the Solar Wind
  6. Launches and Orbital Operations - 2013 - Launches to Orbit and Beyond
  7. Orbital Sciences Corp's Cygnus (Spacecraft) (US)
  8. SpaceX's Dragon (Spacecraft) (US) - SpaceX CSR2 Mission
  9. SpaceX Poised to Launch Cargo from Historic NASA Pad.
  10. SpaceX, NASA Hail 1st Falcon 9 Rocket Launch from Pad Steeped in History.
  11. Lockheed Martin's Orion (Spacecraft) (US)
  12. Sierra Nevada Corporation (SNC)'s Dream Chaser (Spacecraft) (US)
  13. NASA's Solar Probe Blasts Off to the Sun
  14. NASA's Planet-Hunter Caught Stunning Video of a Distant Comet
  15. NASA's Parker Solar Probe Launches on a Mission to Study the Sun and its Dangers
  16. NASA Created a Rare, Exotic State of Matter in Space
  17. NASA: The Space Shuttle and Its Operations
  18. NASA Spacecraft Rockets Toward Sun for Closest Look Yet
  19. NASA Launches Parker Solar Probe Mission to Study the Sun up Close
  20. Life in the Universe: Proceedings of a conference held at NASA Ames Research Center Moffet Field, California, June 19-20, 1979.
  21. Proceedings of the X-15 First Flight 30th Anniversary Celebration of June 8, 1989.
  22. Computers in Spaceflight: The NASA Experience.
  23. Apollo 13 "Houston, we've got a problem."
  24. On the Moon with Apollo 16: A Guide to the Descartes Region.
  25. Skylab: A Guidebook.
  26. Spacelab: An International Short-Stay Orbiting Laboratory.
  27. A Meeting with the Universe: Science Discoveries from the Space Program.
  28. Science in Orbit: The Shuttle & Spacelab Experience: 1981-1986.
  29. Results of the Second Manned Suborbital Space Flight, July 21, 1961.
  30. Results of the Second U.S. Manned Orbital Space Flight.
  31. Results of the Third U.S. Manned Orbital Space Flight.
  32. Mercury Project Summary including Results of the Fourth Manned Orbital Flight
  33. X-15 Research Results With a Selected Bibliography.
  34. Exploring Space with a Camera.
  35. Aerospace Food Technology.
  36. Pioneer Odyssey.
  37. Apollo Expeditions to the Moon.
  38. Apollo Over the Moon: A View From Orbit.
  39. Introduction to the Aerodynamics of Flight.
  40. Biomedical Results of Apollo.
  41. Skylab EREP Investigations Summary.
  42. Skylab: Our First Space Station.
  43. Skylab, Classroom in Space.
  44. A New Sun: Solar Results from Skylab.
  45. Skylab's Astronomy and Space Sciences.
  46. The Space Shuttle.
  47. The Search For Extraterrestrial Intelligence.
  48. Atlas of Mercury.
  49. The Voyage of Mariner 10: Mission to Venus and Mercury.
  50. The Martian Landscape.
  51. The Space Shuttle at Work.
  52. Project Orion: A Design Study of a System for Detecting Extrasolar Planets.
  53. Wind Tunnels of NASA.
  54. Viking Orbiter Views of Mars.
  55. The High Speed Frontier: Case Histories of Four NACA Programs, 1920-1950.
  56. The Star Splitters: The High Energy Astronomy Observatories.
  57. Planetary Geology in the 1980s.
  58. Quest for Performance: The Evolution of Modern Aircraft.
  59. The Long Duration Exposure Facility (LDEF): Mission 1 Experiments.
  60. Voyager 1 and 2, Atlas of Saturnian Satellites.
  61. Far Travelers: The Exploring Machines.
  62. The Impact of Science on Society.
  63. Living Aloft:  Human Requirements for Extended Spaceflight.
  64. Dynamics of Flight | NASA
  65. Aerodynamics of Flight | FAA
  66. Space Shuttle Avionics System.
  67. Flight Research at Ames, 1940-1997.
  68. Unmanned Space Project Management: Surveyor and Lunar Orbiter.
  69. The Planetary Quarantine Program.
  70. Constellation Program Lessons Learned Volume 1: Executive Summary.
  71. Spaceborne Digital Computer Systems.
  72. Celebrating a Century of Flight.
  73. Wings in Orbit: Scientific and Engineering Legacies of the Space Shuttle.
  74. Present and Future State of the Art in Guidance Computer Memories.
  75. History of Research in Space Biology and Biodynamics at the Air Force Missile Development Center, Holloman Air Force Base, New Mexico, 1946-1958.
  76. Report of the Apollo 13 Review Board.
  77. Report of the Presidential Commission on the Space Shuttle Challenger Accident, June 1986 and Implementations of the Recommendations, June 1987.
  78. Transiting from Air to Space: The North American X-15.
  79. Space Handbook: Astronautics and Its Applications.
  80. Probing the Sky: Selected NACA Research Airplanes and Their Contributions to Flight
  81. The First Century of Flight: NACA/NASA Contributions to Aeronautics.
  82. Space Station Requirements and Transportation Options for Lunar Outpost.
  83. Space Station Freedom Accommodation of the Human Exploration Initiative.
  84. The Story of Self-Repairing Flight Control Systems.
  85. Ideas Into Hardware: A History of the Rocket Engine Test Facility at the NASA Glenn Research Center.
  86. Guide to Magellan Image Interpretation.
  87. Magellan: The Unveiling of Venus.
  88. The Apollo Program Summary Report.
  89. Saturn Illustrated Chronology.
  90. See How It Flies
  91. Introduction to the Aerodynamics of Flight.
  92. Aerodynamics Q&A
  93. UIUC Airfoil Data
  94. Beginner's Guide to Aerodynamics
  95. Beginner's Guide to Compressible Aerodynamics
  96. Beginner's Guide to Wind Tunnels
  97. FoilSim III
  98. Aircraft Design: Synthesis and Analysis
  99. Modeling Flight
  100. Unmanned Aerial Vehicles
  101. NASA Beginner's Guide to Propulsion
  102. NASA Langley Aircraft Photo Collection
  103. The 8 Planets in Our Solar System
  104. The 5 Dwarf Planets
  105. Other Objects in The Solar System
  106. Space Mega-projects
  107. Wide Field Infrared Survey Telescope: A planned wide field infrared space telescope by NASA.


Presidential Aeronautics and Space Reports


NASA History Year in Review


Astronomy & Astronauts
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Astronomy

Astro Watch -- About Astronomy -- Absolute Astronomy -- Astronomy -- Astronomy Magazine -- Astronomy Notes -- Astronomy Now -- Astro Watch -- Astronomy Society -- American Astronomical Society -- Astronomy for Beginners -- Astronomy Q&A -- Deep Astronomy -- Dot Astronomy -- Earth Viewer -- Encyclopedia of Astronomy and Astrophysics -- Images of Space -- Hubble Telescope -- Kids Astronomy -- NASA Kids Club -- NASA Spacelink -- Physics Astronomy Life -- Planet Diary -- Planet Facts -- Radio Astronomy Observatory -- Royal Observatory Edinburgh -- Science & Astronomy -- Science World: Astronomy -- Sea & Sky -- Sky & Telescope -- Slooh -- Solar Space Station -- The Da Vinci Astronomy .

Astronauts Resources

Astronaut Information Summary -- Astronaut -- Astronaut Selection -- U.S. Astronaut Biographies -- Female Astronauts -- Women of Space -- Women in Space.

Astronauts



NASA Astronauts

  • Active Astronauts
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  • Former Astronauts
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  • Partner Astronauts
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