Field guide · 121 entries
Space Codex
A field guide to the Solar System and beyond, built from NASA, ESA and JPL data.
Planets, moons, small bodies, exoplanets, galaxies, the strangest objects in the sky and the missions that measure them. Every value links to the source it came from, numbers that change carry the month we last confirmed them, and where a world is part of our real-time 3D model, its entry explains first-hand how we draw it.
Scale ladder
How far light travels
From Earth to the edge of what we can see, measured in the time light takes to cross the gap. Each step is a leap of orders of magnitude.
Earth
0 secondsWhere every measurement starts.The Moon
1.3 light-seconds384,400 km on average.The Sun
8.3 light-minutesOne astronomical unit.Heliopause
≈16.6 light-hoursAbout 120 AU, where the solar wind meets interstellar space.Nearest star
4.24 light-yearsProxima Centauri and its planet b.Milky Way centre
≈26,000 light-yearsThe Sun to Sagittarius A*.Andromeda
≈2.5 million light-yearsThe nearest large spiral galaxy.Observable universe
≈13.8 billion years of light travelLight-travel time of the cosmic microwave background, the oldest light we can see.
Bars use a logarithmic scale of light-time in seconds. The last step is a lookback time: the universe has expanded since that light set out, so the matter that emitted it is now much farther away.
Sun & planets
Our star and the eight worlds that orbit it.
The Sun
In 3DG2V main-sequence star · 4.6 billion years old
- Spectral type
- G2V
Mercury
In 3DSmallest planet · iron-heavy and airless
- Distance from Sun
- 0.39 AU
Venus
In 3DRunaway greenhouse twin of Earth
- Distance from Sun
- 0.72 AU
Earth
In 3DThe only known world with life
- Distance from Sun
- 1.00 AU
Mars
In 3DCold desert with an ancient wet past
- Distance from Sun
- 1.52 AU
Jupiter
In 3DLargest planet · gas giant
- Distance from Sun
- 5.20 AU
Saturn
In 3DRinged gas giant
- Distance from Sun
- 9.54 AU
Uranus
In 3DIce giant tipped on its side
- Distance from Sun
- 19.2 AU
Neptune
In 3DWindiest world · found by mathematics
- Distance from Sun
- 30.1 AU
Moons
The major moons, from our own to Triton.
The Moon
In 3DEarth's only natural satellite
- Mean radius
- 1,737.4 km (0.273 Earth)
Phobos
In 3DMars's doomed inner moon
- Dimensions
- 27 × 22 × 18 km
Deimos
In 3DMars's small, smooth outer moon
- Dimensions
- 15 × 12 × 11 km
Io
In 3DThe most volcanic world known
- Mean radius
- 1,821.5 km
Europa
In 3DAn ocean world under ice
- Mean radius
- 1,560.8 km (about 90% of the Moon)
Ganymede
In 3DThe largest moon in the Solar System
- Mean radius
- 2,631.2 km
Callisto
In 3DThe most heavily cratered object known
- Mean radius
- 2,410.3 km
Mimas
In 3DThe 'Death Star' moon with a hidden ocean
- Dimensions
- 208 × 197 × 191 km
Enceladus
In 3DThe moon that sprays its ocean into space
- Dimensions
- 257 × 251 × 248 km
Tethys
In 3DIce moon split by a giant canyon
- Mean radius
- 531.1 km
Dione
In 3DCratered moon laced with ice cliffs
- Mean radius
- 561.4 km
Rhea
In 3DSaturn's second-largest moon
- Mean radius
- 763.5 km
Titan
In 3DA moon with weather, rivers and seas
- Mean radius
- 2,574.8 km (second-largest moon)
Iapetus
In 3DThe two-faced moon
- Dimensions
- 746 × 746 × 712 km
Miranda
In 3DA patchwork moon with record cliffs
- Mean radius
- 235.8 km
Ariel
In 3DUranus's youngest, brightest face
- Mean radius
- 578.9 km
Umbriel
In 3DThe darkest of Uranus's large moons
- Mean radius
- 584.7 km
Titania
In 3DUranus's largest moon
- Mean radius
- 788.9 km
Oberon
In 3DThe outermost major moon of Uranus
- Mean radius
- 761.4 km
Triton
In 3DA captured world orbiting backwards
- Mean radius
- 1,352.6 km
Charon
In 3DPluto's half-sized partner
- Mean radius
- 606 km (about half of Pluto)
Dwarf planets
Round worlds that never cleared their orbits.
Pluto
In 3DDwarf planet · heart of the Kuiper belt
- Mean radius
- 1,188.3 km (0.19 Earth)
Dwarf planet · largest body in the asteroid belt
- Mean diameter
- 939.4 km
Small bodies
Asteroids, comets, the Kuiper belt and interstellar visitors.
Rocky debris between Mars and Jupiter
- Region
- About 2.2–3.3 AU from the Sun
A layered protoplanet
- Mean diameter
- 522.8 km (569 × 554 × 453 km)
16 Psyche
Artist's conceptA metal-rich world NASA is flying to
- Mean diameter
- About 222 km (278 × 238 × 171 km)
Rubble-pile asteroid sampled by OSIRIS-REx
- Size
- About 0.49 km (505 × 492 × 457 m)
Diamond-shaped asteroid sampled by Hayabusa2
- Size
- About 0.9 km
The asteroid that will skim Earth in 2029
- Size
- About 340 m
The icy disc beyond Neptune
- Region
- About 30–50 AU from the Sun
The most distant world explored up close
- Length
- About 36 km (contact binary)
The Solar System's distant icy shell
- Inner edge
- About 2,000–5,000 AU
The most famous comet
- Orbital period
- About 76 years
The comet Rosetta orbited
- Orbital period
- 6.43 years
1I/ʻOumuamua
Artist's conceptThe first known interstellar visitor
- Discovered
- 19 Oct 2017 by Pan-STARRS1
The first interstellar comet
- Discovered
- 30 Aug 2019 by Gennadiy Borisov
The third interstellar object, and the fastest
- Perihelion
- 29 Oct 2025 at 1.36 AU
Exoplanets
Worlds around other stars, measured but never photographed up close.
Planets around other stars
- Confirmed exoplanets
- 6,445
TRAPPIST-1
In 3DArtist's conceptSeven Earth-sized worlds · about 40.5 light-years
- Distance
- About 40.5 light-years (12.43 pc)
Proxima Centauri b
In 3DArtist's conceptThe nearest exoplanet · 4.24 light-years
- Distance
- 4.24 light-years
Kepler-186f
Artist's conceptFirst Earth-size planet found in a habitable zone
- Distance
- About 579 light-years
Kepler-452b
Artist's conceptAn 'Earth cousin' that may not be real
- Distance
- About 1,800 light-years
K2-18 b
In 3DArtist's conceptA sub-Neptune at the centre of a biosignature debate
- Distance
- About 124 light-years
55 Cancri e
In 3DArtist's conceptA lava world with a variable atmosphere
- Distance
- About 41 light-years
WASP-39 b
Artist's conceptJWST's first exoplanet carbon dioxide
- Distance
- About 700 light-years
WASP-76 b
Artist's conceptWhere it may rain iron
- Distance
- About 634 light-years
HD 189733 b
In 3DArtist's conceptA cobalt-blue world that smells of rotten eggs
- Distance
- About 64.5 light-years
LHS 1140 b
In 3DArtist's conceptA temperate super-Earth, possibly icy
- Distance
- About 48.9 light-years
TOI-700 d
Artist's conceptTESS's first Earth-size habitable-zone world
- Distance
- About 101.5 light-years
Kepler-16 b
Artist's conceptA real world with two suns
- Distance
- About 245 light-years
PSR B1257+12 planets
Artist's conceptThe first exoplanets ever confirmed
- Distance
- About 2,000 light-years (uncertain)
WASP-12 b
Artist's conceptA pitch-black planet spiralling into its star
- Distance
- About 1,390 light-years
HR 8799
Artist's conceptFour giant planets photographed directly
- Distance
- About 134.5 light-years
51 Pegasi b
Artist's conceptThe planet that started it all
- Distance
- About 50.4 light-years
Galaxies
Our galaxy, its neighbours and the earliest galaxies seen.
Andromeda Galaxy
In 3DM31 · the nearest large spiral
- Distance
- ~2.5 million ly
Our barred spiral home galaxy
- Type
- Barred spiral
M33 · the third large Local Group spiral
- Distance
- About 3 million light-years
The Milky Way's biggest satellite
- Type
- Barred Magellanic irregular
An irregular dwarf, stretched by its neighbours
- Distance
- About 204,000 light-years (62.4 kpc)
Giant elliptical with the first imaged black hole
- Distance
- About 54–55 million light-years
M104 · a bright bulge ringed by dust
- Distance
- About 28–30 million light-years
M51 · the textbook grand-design spiral
- Distance
- About 25–31 million light-years
M101 · nearly twice the Milky Way's width
- Distance
- About 21–25 million light-years
The nearest active galaxy
- Distance
- About 13 million light-years
A ring galaxy made by a collision
- Collision
- About 400–440 million years ago
Four interacting galaxies and an interloper
- Distance
- About 290 million light-years (NGC 7320: about 40 million)
Two spirals merging
- Distance
- About 45–65 million light-years
The most distant galaxies confirmed
- Record holder
- MoM-z14, redshift 14.44
Filaments, voids and Laniakea
- Observable universe
- About 93 billion light-years across
Nebulae
Clouds where stars are born, and the shells they leave behind.
Orion Nebula
In 3DM42 · the nearest large stellar nursery
- Distance
- About 1,300–1,350 light-years
M1 · the wreck of the supernova of 1054
- Distance
- About 6,500 light-years (Taurus)
Star-forming columns in the Eagle Nebula
- Distance
- About 6,500 light-years (M16)
The edge of a star-carved cavity
- Distance
- About 7,600 light-years
M57 · a dying Sun-like star
- Distance
- About 2,500 light-years
The nearest bright planetary nebula
- Distance
- About 650 light-years
Phenomena
Black holes, neutron stars, cosmic signals and the shape of the universe.
Black hole
In 3DEvent horizon · gravity light cannot escape
- Innermost stable orbit
- 3 horizon radii (non-spinning)
Wormhole
In 3DA hypothetical shortcut through spacetime
- Throat tension (10 m throat)
- About 5 × 10⁴⁰ Pa
The bubble blown by the solar wind
- Termination shock (Voyager 1)
- Dec 2004 at 94 AU
The black hole at the centre of the Milky Way
- Mass
- 4.30 million solar masses
The first black hole ever imaged
- Mass
- 6.5 billion solar masses
City-sized stellar cores
- Diameter
- About 20 km
Cosmic lighthouses
- Known pulsars
- 4,393 in the ATNF catalogue
The strongest magnets in the universe
- Field strength
- About 1,000 times a normal neutron star's
How stars explode
- Core collapse
- Stars above about 8 solar masses; about 99% of the energy leaves as neutrinos
Feeding supermassive black holes
- First identified
- 3C 273, by Maarten Schmidt in 1963
The brightest gamma-ray burst ever recorded
- Brightness
- About 70× the previous record holder
Millisecond flashes from across the universe
- Milky Way source
- Magnetar SGR 1935+2154 (2020)
Ripples in spacetime
- Confident detections
- 390 (through GWTC-5.0)
The oldest light in the universe
- Temperature
- 2.7255 K
The 95% we cannot see
- Ordinary matter
- About 4.9%
13.8 billion years in one view
- Cosmic microwave background
- About 380,000 years
Missions
The spacecraft doing the measuring.
Voyager 1
In 3DFirst spacecraft in interstellar space
- One light-day from Earth
- 18 Nov 2026, 10:16:07 UTC
The only visitor to Uranus and Neptune
- Launched
- Aug 1977
NASA's ocean-world explorer
- Launched
- 14 Oct 2024
ESA's Jupiter Icy Moons Explorer
- Launched
- 14 Apr 2023
ESA–JAXA Mercury mission
- Launched
- Oct 2018
JAXA's Phobos sample return
- Rocket
- H3 Flight 10, Tanegashima
NASA's return to the Moon
- Artemis II
- 1–10 Apr 2026, crewed lunar flyby
China's lunar south-pole mission
- Spacecraft
- Orbiter, lander, rover and hopper
NASA's Jupiter polar orbiter
- Launched
- Aug 2011
A rotorcraft for Titan
- Arrival
- Late 2034
NASA's journey to a metal-rich asteroid
- Launched
- Oct 2023
Parker Solar Probe
In 3DThe fastest human-made object
- Top speed
- About 692,000 km/h (430,000 mph)
Pluto and the Kuiper belt
- Launched
- 19 Jan 2006
Infrared observatory at L2
- First clear exoplanet CO₂
- WASP-39 b (announced Aug 2022)
Crewed laboratory in low Earth orbit
- Altitude
- About 400 km (250 mi)
Topics
Short explainers for the big questions.
Gravity so strong light cannot escape
- First image
- M87*, Event Horizon Telescope, 2019
A hypothetical tunnel through spacetime
- Status
- Theoretical
Beyond Earth's neighbourhood
- Nearest star
- Proxima Centauri, 4.24 light-years
Our barred spiral home galaxy
- Type
- Barred spiral
Clouds where stars are born or die
- Hydrogen glow
- Deep red H-alpha at 656 nm
Island universes in an expanding cosmos
- Nearest large galaxy
- Andromeda, about 2.5 million ly
Method
How the Codex is built
Sourced, value by value
Physical values come from JPL Solar System Dynamics and NASA's planetary fact sheets, exoplanets from the NASA Exoplanet Archive, and deep-sky objects from ESA, ESO and peer-reviewed papers. Each row names its source.
Dated where it drifts
Moon counts, mission status and record holders change. Those values carry an “as of” month, every entry shows when it was last reviewed, and a test fails when a volatile value goes stale.
Rendered first-hand
For the bodies in our 3D model, each entry describes how we actually draw it: the maps, the shaders and the compromises, such as sizes and distances that are not to scale.
The Space Codex is independent work by A Few Good Coders. It uses public data and images under their published terms and is not affiliated with or endorsed by NASA, ESA, ESO, JPL or any other agency. Entries marked “Artist's concept” describe worlds no telescope has imaged as more than a point of light.
Interactive 3D on the web
See it moving.
The same data drives a real-time model of the Sun, the planets, their major moons, a ray-traced black hole and a wormhole, running in your browser.