Curated category
Solar System
- Solar SystemThe Sun holds 99.86% of all the mass in the Solar System. Everything else, the eight planets, the dwarf planets, the moons, the asteroids and comets…
- Mercury (planet)Mercury is the first planet from the Sun and the smallest in the Solar System, with an equatorial radius of 2439.7 km. It is so close to the Sun that it…
- SednoidSedna sits roughly 84 AU from the Sun today, drifting through a darkness so profound that it will not reach its closest approach to the Sun for several…
- Detached objectDetached objects orbit the Sun in the outermost reaches of the Solar System, so far from every planet that they seem to belong to no neighbourhood at all.
- Moons of PlutoPluto has five known moons, and the story of how we came to know that fact is a lesson in how wrong our assumptions can be.
- Terrestrial planetMercury, Venus, Earth, and Mars share something no other planets in our Solar System can claim: they are made of rock and metal rather than gas.
- HaumeaHaumea is a dwarf planet so strange that astronomers initially struggled to believe what they were seeing. Spinning faster than any other large body in the…
- Dysnomia (moon)Dysnomia orbits a world so far from the Sun that sunlight takes more than five hours to reach it. It is the only known moon of the dwarf planet Eris, and its…
- Io (moon)Io has over 400 active volcanoes, more than any other object in the Solar System. Several of them fire plumes of sulfur and sulfur dioxide as high as 500 km…
- Galilean moonsThe Galilean moons are four worlds circling Jupiter, each one large enough to rank among the biggest objects in the Solar System.
- Europa (moon)Europa, the smallest of Jupiter's four Galilean moons, holds a secret beneath its frozen skin that has captivated scientists for decades.
- Scattered discThe scattered disc sits at the outermost edges of our Solar System, a vast and sparsely populated zone where icy bodies trace some of the most extreme orbits…
- PlutoPluto sits roughly 39.5 AU from the Sun, so far away that sunlight takes 5.5 hours just to reach it. When Clyde Tombaugh spotted a faint moving speck on…
- 4 Vesta4 Vesta sits in the asteroid belt between Mars and Jupiter, and on the 29th of March 1807 a German astronomer named Heinrich Wilhelm Matthias Olbers spotted…
- Moons of NeptuneThe moons of Neptune tell a story of cosmic violence, improbable captures, and a solar system still bearing the scars of one catastrophic arrival.
- Human spaceflightHuman spaceflight has been continuous since the 2nd of November 2000, when the first crew boarded the International Space Station and never fully left.
- Callisto (moon)Callisto hangs in the darkness beyond Jupiter's main radiation belt, orbiting at a distance of roughly 1.883 million kilometers from the planet it…
- MakemakeMakemake is a dwarf planet drifting in the frozen outer reaches of the Solar System, so far from Earth that even the most powerful telescopes see it only as…
- Moons of MarsThe moons of Mars, Phobos and Deimos, were discovered by American astronomer Asaph Hall in August 1877 and named for the twin sons of Ares who accompanied…
- CometA comet can stretch an arc of up to 30 degrees across the night sky, the span of sixty full Moons. That is what a comet looks like when it is close and…
- PlanetA planet is a large, rounded astronomical body, and for centuries the word meant something humble: a point of light that wandered.
- Natural satelliteA natural satellite is an astronomical body that orbits a planet, a dwarf planet, or a small Solar System body, and sometimes even another natural satellite.
- Kuiper beltThe Kuiper belt begins where Neptune ends, at 30 astronomical units from the Sun, and stretches out to roughly 50 AU. It is a vast ring of small frozen…
- Discovery and exploration of the Solar SystemDiscovery and exploration of the Solar System stretches across millennia, from the first humans who watched the Sun fix the cardinal directions at dawn and…
- Space colonizationSpace colonization is the idea that human beings might one day build permanent settlements beyond Earth, on other planets, moons, asteroids, and perhaps even…
- Eris (dwarf planet)Eris, minor-planet number 136199, upended the Solar System's address book in a single announcement on the 29th of July 2005.
- SunThe Sun fuses about 600 billion kilograms of hydrogen into helium every second. In that same second, 4 billion kilograms of matter vanish, converted entirely…
- AsteroidAn asteroid is a minor planet, an object larger than a meteoroid that is neither a planet nor an identified comet, orbiting within the inner Solar System.
- Moons of SaturnSaturn has 292 confirmed moons as of the 9th of April 2026 - more than any other planet in the Solar System. That number alone is staggering, but what makes…
- Formation and evolution of the Solar SystemThe formation and evolution of the Solar System began not with a burst of light, but with a quiet collapse. About 4.6 billion years ago, a fragment of a…
- Deimos (moon)Deimos is the smaller and outer of the two moons of Mars, and it carries the name of dread itself. In Greek mythology, Deimos personified terror, a companion…
- Moons of UranusThe moons of Uranus carry names borrowed from English literature rather than Greek mythology, a deliberate choice that set them apart from every other moon…
- Trojan (celestial body)Trojan celestial bodies are small objects sharing the orbit of a larger neighbor, hovering roughly 60 degrees ahead or behind it in a gravitational sweet…
- AstronomyAstronomy is one of the oldest natural sciences, and its earliest practitioners had no telescopes at all. Before recorded history, people stacked great…
- SpaceflightSpaceflight is the use of astronautics to fly objects, usually spacecraft, into or through outer space, with or without humans on board.
- Space explorationSpace exploration begins not with a triumphant launch but with a German rocket climbing 176 kilometers into the dark on the 20th of June 1944.
- Moons of JupiterJupiter's moons number 115 at last count, and the tally is still climbing. That figure alone should give you pause. Earth has one moon. Mars has two.
- Asteroid beltThe asteroid belt sits in a gap that has puzzled astronomers for more than four centuries. In 1596, Johannes Kepler wrote in his Mysterium Cosmographicum…
- Oort cloudThe Oort cloud is a vast, theorized shell of billions of icy bodies surrounding the Sun at distances so extreme they are measured in tens of thousands of…
- Saturn's hexagonSaturn's hexagon is a cloud formation sitting above the planet's north pole, and it is unlike anything else in the known solar system.
- EarthEarth is the third planet from the Sun, and the only place in the known universe where life has ever taken hold. At 4.5 billion years old, it formed from gas…
- MoonThe Moon is the only natural satellite of Earth, and it orbits at an average distance of 384,399 km. That gap is roughly thirty times the width of Earth.
- Exploration of the MoonThe Exploration of the Moon began not with a rocket, but with a rock carving. At Knowth in Ireland, a stone face dated to around 3,000 BCE bears what…
- Minor-planet moonA minor-planet moon is a natural satellite in orbit around a minor planet, and as of the latest count, astronomers have identified 625 minor planets known or…
- Planet NinePlanet Nine is the name astronomers Konstantin Batygin and Michael Brown gave to a hypothetical ninth planet lurking in the outermost reaches of the Solar…
- Trans-Neptunian objectTrans-Neptunian objects, or TNOs, are the remote sentinels of our Solar System, orbiting the Sun at distances greater than Neptune's average of 30.1…
- Solar System modelA 1766 Benjamin Martin mechanical model sits on display at the Harvard Collection of Historical Scientific Instruments. This orrery illustrates the relative…
- Deep space explorationDeep space exploration sits at the edge of what humanity can actually reach. On the 25th of August 2012, Voyager 1 crossed into interstellar space, becoming…
- Local BubbleThe Local Bubble is the vast, thinly filled cavity of space that the Solar System currently calls home. At least 1,000 light years across, it sits within the…
- Small Solar System bodyIn August of 2006, the International Astronomical Union gathered in Prague to vote on a new definition for planets. The resolution passed by a narrow margin…