Space Codex

A field guide to our universe.

408 entries: worlds close to home, the physics behind them, and a reference collection of nearby exoplanets.

Start with a planet or moon, follow an explanation of how it works, or compare published measurements from other star systems. Object guides describe the physical story; reference profiles keep the values, uncertainties, and research links together.

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Worlds, stars, and galaxies

Alpha CentauriAlpha Centauri is a nearby three-star system: a Sun-like pair, A and B, plus distant red dwarf Proxima.
Andromeda GalaxyAndromeda is the nearest large spiral galaxy to the Milky Way, with a complex stellar history and an uncertain future encounter.
Asteroid BeltThe main asteroid belt is a wide, mostly empty region between Mars and Jupiter whose diverse bodies preserve early Solar System history.
BennuBennu's rubble-pile structure, changing orbit and returned sample reveal how a near-Earth asteroid is studied.
Black HolesBlack holes are regions bounded by event horizons, studied through gravity, hot nearby matter and gravitational waves.
CallistoCallisto's cratered exterior and possible ocean preserve a different branch of Jupiter's moon history.
CeresCeres is the largest belt object, with bright salt deposits, a water-rich interior and a history revealed by Dawn.
CharonCharon and Pluto form a tightly linked pair, with mutual tidal locking, deep fractures and a record of early ice-world change.
EarthGet to know Earth: its day and year, seasons, atmosphere, ocean, moving interior, and the observations that connect them.
EnceladusEnceladus sprays material from a buried ocean into space, offering a rare chance to study ocean chemistry without drilling.
EuropaEuropa's fractured ice, likely global ocean, tidal heating and radiation make this Jovian moon a compelling but unresolved habitability study.
GanymedeGanymede is the largest moon, with grooved ice, a magnetic field and strong evidence for a buried ocean.
Halley's CometHalley's Comet returns roughly every 76 years, linking a changing ice-and-dust body with centuries of recorded skywatching.
IoIo is the Solar System's most volcanic world. Learn how orbital resonance, solid-body tides, lava and sulfur dioxide reshape it.
JupiterExplore Jupiter's hydrogen-rich atmosphere, powerful storms and magnetic field, faint rings, and the varied worlds of its four large moons.
Kuiper BeltBeyond Neptune, the Kuiper Belt holds icy bodies on many kinds of orbit and records the giant planets' early migration.
MarsRead about Mars, from its thin atmosphere and long seasons to ancient lakes, remaining water ice, and the evidence gathered by spacecraft.
MercuryMeet Mercury: its short year, long solar day, cratered surface, thin exosphere, magnetic field, and ice in permanently shadowed polar craters.
The Milky WayMap our place in the Milky Way: its disk, spiral arms, stellar motions, central black hole, and why face-on portraits are scientific reconstructions.
The MoonExplore the Moon's phases, tidal lock, ancient lava plains, crater record, polar ice, and the difference between a lunar month and one orbit.
NeptuneRead about Neptune's long year, fast winds, shifting storms, dark rings, and Triton, while separating image color from the planet's physical properties.
Neutron StarsNeutron stars pack more than a Sun's mass into a city-scale body, producing pulsars, strong fields and extreme matter.
Oort CloudThe Oort Cloud is an inferred distant reservoir of icy bodies, proposed to explain long-period comets from many directions.
Orion NebulaThe Orion Nebula is a nearby star-forming region where young stars, gas, dust and radiation shape a visible cloud.
PleiadesThe Pleiades are a young nearby star cluster whose bright stars, dust and extended membership reveal how stellar families disperse.
PlutoGet to know Pluto as a Kuiper Belt dwarf planet with a thin seasonal atmosphere, nitrogen-ice plains, mountains, and the large companion Charon.
Proxima CentauriProxima Centauri is our nearest known stellar neighbor, a faint red dwarf with planets whose conditions remain uncertain.
Sagittarius A*Sagittarius A* is the compact black hole at the Milky Way's center, measured through stellar orbits and glowing nearby gas.
SaturnRead Saturn's rings as a changing system, then meet its hydrogen-rich atmosphere, polar hexagon, and the remarkable moons Titan and Enceladus.
The SunUnderstand the Sun: fusion, plasma, the corona, solar wind, magnetic activity, and the spacecraft studying our nearest star.
TitanTitan has dense nitrogen air, methane weather, hydrocarbon seas and a still-debated deep interior.
TRAPPIST-1Seven roughly Earth-sized planets circle the small star TRAPPIST-1; their sizes and orbits are measured, while atmospheres remain under study.
TritonTriton's backward orbit, nitrogen ice, active-looking surface and Voyager plumes point toward a captured outer Solar System world.
UranusLearn why Uranus rotates on its side, what an ice giant really is, and how its faint rings, long seasons, methane clouds, and magnetic field are studied.
VenusUnderstand Venus through its dense atmosphere, extreme greenhouse heat, backward spin, volcanic terrain, sulfuric-acid clouds, and radar mapping.
VestaVesta's basaltic crust, giant south-polar basin and meteorite links show how a small world can partly become planet-like.

How space works

Exoplanet reference

These profiles describe a selected published solution for each planet. They are separate from the interactive atlas and its sponsorship inventory. For a focused list, browse the exoplanet collection.

Sources and editorial approach

The object and concept guides link scientific sources. Numerical exoplanet profiles use NASA Exoplanet Archive Planetary Systems default rows, retrieved for this edition. Missing measurements, uncertainty intervals, minimum masses, and model temperatures keep their labels. Surface conditions are not invented to fill a table.

Research and the archive can change. Follow a profile’s reference for the underlying fit and its publication date. Space Pixel is an independent educational product; source attribution does not imply NASA endorsement.