Atlas

Star at the center of the solar system

Sun

Named for: Latin sol, the root of the word solar. Helios, the Greek god of the Sun, gives words such as heliosphere.
Age: 4.6 billion years. The Sun formed when a cloud of gas and dust collapsed under its own gravity.
Diameter: 1,391,400 km, 109 times Earth's
Mass: 1.99 × 10³⁰ kg, about 333,000 Earths
Gravity: 274 m/s² at the visible surface, 28 times Earth's
Escape velocity: 617.6 km/s
Rotation: 25.4 days at 16° latitude. The equator turns faster than the poles.
Distance from Earth: 147.1 million to 152.1 million km
Temperature: 5,500 °C (9,930 °F, 5,772 K) at the visible surface. 15.7 million K (28.3 million °F) in the core.
Composition: Hot, electrically charged gas, mostly hydrogen and helium. The visible surface is 91.0 percent hydrogen and 8.9 percent helium by number of atoms, with traces of oxygen, carbon, neon, nitrogen, iron, magnesium, silicon and sulfur. Hydrogen fusing into helium in the core powers its light and heat.
Power output: 3.83 × 10²⁶ watts

Sources: NASA Sun Fact Sheet, NASA Science, Sun facts

First planet from the Sun

Mercury

Named for: Mercury, the Roman messenger god, known for his speed. The planet orbits the Sun faster than any other planet, once every 88 days.
Age: 4.5 billion years
Discovered: Visible without a telescope and recorded since ancient times. No discoverer is known.
Distance from the Sun: 57.9 million km on average (0.387 AU)
Distance from Earth: 77.3 million to 221.9 million km
Diameter: 4,879 km, 0.38 times Earth's
Mass: 3.30 × 10²³ kg, 0.055 Earths
Gravity: 3.7 m/s², 38 percent of Earth's
Escape velocity: 4.3 km/s
Day: 176 Earth days from one sunrise to the next. Measured against the stars, Mercury rotates once every 58.6 Earth days.
Year: 88.0 Earth days
Temperature: 430 °C (806 °F) in daylight, −180 °C (−292 °F) at night
Atmosphere: Nearly none. Its trace of gas is below 0.005 picobar.
Sunlight: 9,083 W/m², 6.7 times what Earth receives
Composition: Metal core 2,074 km in radius, 85 percent of the planet's radius, partly molten. Rocky mantle and crust 400 km thick. Second densest planet after Earth.
Moons: None

Part of the area around the south pole has no image and shows as a plain tone.

Map: MESSENGER images (NASA, Johns Hopkins APL, Carnegie Institution of Washington), USGS Astrogeology mosaic, tinted to Mercury's color.

Sources: NASA Mercury Fact Sheet, NASA Science, Mercury facts, NASA Science, Venus facts (the seven objects the Romans named)

Second planet from the Sun

Venus

Named for: Venus, the Roman goddess of love and beauty, Aphrodite to the Greeks.
Age: 4.5 billion years
Discovered: Visible without a telescope and recorded since ancient times. No discoverer is known. Early observers took it for two objects, a morning star and an evening star.
Distance from the Sun: 108.2 million km on average (0.723 AU)
Distance from Earth: 38.2 million to 261.0 million km
Diameter: 12,104 km, 0.95 times Earth's
Mass: 4.87 × 10²⁴ kg, 0.815 Earths
Gravity: 8.9 m/s², 90 percent of Earth's
Escape velocity: 10.4 km/s
Day: 117 Earth days from one sunrise to the next. Measured against the stars, Venus rotates once every 243 Earth days, east to west, the reverse of Earth's direction.
Year: 224.7 Earth days
Temperature: 464 °C (867 °F, 737 K), day and night. Hottest planet in the solar system.
Atmosphere: 92 bar, about 90 times Earth's air pressure at sea level. Carbon dioxide 96.5 percent, nitrogen 3.5 percent.
Sunlight: 2,601 W/m², 1.9 times what Earth receives
Composition: Iron core, hot rocky mantle, thin rocky crust. Built much like Earth.
Moons: None

North of 68° north and south of 59° south, where Akatsuki saw the planet only at a slant, the map shows a plain tone.

Map: ultraviolet images of the cloud tops taken by JAXA's Akatsuki spacecraft from November 17 to 24, 2018, each shifted to follow the clouds, which circle Venus in five days (Murakami and colleagues, CC BY 4.0). The map is tinted to Venus's color. To the eye, the patterns are fainter than in ultraviolet light.

The strips Magellan's radar missed and the area south of 82° south show as a plain tone on the surface map.

Surface map: Magellan radar images (NASA/JPL), USGS Astrogeology global mosaic.

Sources: NASA Venus Fact Sheet, NASA Science, Venus facts

Third planet from the Sun

Earth

Named for: Old English and Germanic words for the ground.
Age: 4.5 billion years
Distance from the Sun: 149.6 million km on average (1 AU)
Diameter: 12,756 km
Mass: 5.97 × 10²⁴ kg
Gravity: 9.8 m/s²
Escape velocity: 11.2 km/s
Day: 24 hours from one noon to the next. Measured against the stars, Earth rotates once every 23.93 hours.
Year: 365.26 days
Temperature: 15 °C (59 °F, 288 K) on average
Atmosphere: 1.014 bar at sea level. Nitrogen 78.08 percent, oxygen 20.95 percent, argon 0.93 percent, carbon dioxide 0.042 percent.
Sunlight: 1,361 W/m²
Composition: Solid iron and nickel inner core, 1,221 km in radius, up to 5,400 °C (9,750 °F). Liquid iron and nickel outer core, 2,300 km thick. Mantle of hot, slow-flowing rock, 2,900 km thick. Rocky crust.
Moons: 1

Sources: NASA Earth Fact Sheet, NASA Science, Earth facts, Natural Earth, 1:50m land outlines (public domain)

Fourth planet from the Sun

Mars

Named for: Mars, the Roman god of war, for its blood-red color. The Egyptians called it Her Desher, the red one.
Age: 4.5 billion years
Discovered: Visible without a telescope and recorded since ancient times. No discoverer is known.
Distance from the Sun: 228.0 million km on average (1.524 AU)
Distance from Earth: 54.6 million to 401.4 million km
Diameter: 6,792 km, 0.53 times Earth's
Mass: 6.42 × 10²³ kg, 0.107 Earths
Gravity: 3.7 m/s², 38 percent of Earth's
Escape velocity: 5.0 km/s
Day: 24.66 hours, called a sol
Year: 687.0 Earth days
Temperature: −59 °C (−74 °F, 214 K) on average. Highs near 20 °C (68 °F), lows near −153 °C (−243 °F).
Atmosphere: 0.6 percent of Earth's air pressure. Carbon dioxide 95.1 percent, nitrogen 2.59 percent, argon 1.94 percent.
Sunlight: 586 W/m², 43 percent of what Earth receives
Composition: Core of iron, nickel and sulfur, 1,500 to 2,100 km in radius. Rocky mantle 1,240 to 1,880 km thick. Crust of iron, magnesium, aluminum, calcium and potassium, 10 to 50 km deep. Rusted iron in its rock and dust gives Mars its red color.
Moons: 2

Map: Viking Orbiter images (NASA), USGS Astrogeology color mosaic.

Sources: NASA Mars Fact Sheet, NASA Science, Mars facts

Between the orbits of Mars and Jupiter

Asteroid Belt

Age: 4.6 billion years. Asteroids are rocky pieces left over from the formation of the solar system.
Formation: Jupiter's gravity stopped a planet from forming in this region. The same gravity made the small bodies collide and break apart into the asteroids seen today.
Discovered: 1801, when Giuseppe Piazzi spotted Ceres, the first object found in the belt.
Asteroids: Between 1.1 and 1.9 million larger than 1 km across, plus millions of smaller ones.
Sizes: From Vesta, the largest asteroid at 530 km across, down to rocks less than 10 m across.
Largest object: Ceres, a dwarf planet with a radius of 476 km. Ceres orbits the Sun once every 4.6 Earth years.
Mass: All asteroids combined have less mass than Earth's Moon. Ceres contains 25 percent of the belt's mass, and Vesta almost 9 percent of the mass of all asteroids.
Composition: Three broad classes. C-type asteroids outnumber the other two. They are dark and probably made of clay and silicate rocks. S-type asteroids are stony, made of silicate rock and nickel-iron. M-type asteroids are metallic nickel-iron.

Sources: NASA Science, Asteroids facts, NASA Science, Ceres facts, NASA Science, Vesta

Fifth planet from the Sun

Jupiter

Named for: Jupiter, king of the Roman gods. Its moons are named for figures tied to Jupiter or to Zeus, his Greek counterpart.
Age: 4.6 billion years
Discovered: Visible without a telescope and recorded since ancient times. No discoverer is known.
Distance from the Sun: 778.5 million km on average (5.20 AU)
Distance from Earth: 588.5 million to 968.5 million km
Diameter: 142,984 km, 11.2 times Earth's
Mass: 1.90 × 10²⁷ kg, 318 Earths
Gravity: 23.1 m/s² at the cloud tops, 2.4 times Earth's
Escape velocity: 59.5 km/s
Day: 9.93 hours, the shortest of any planet
Year: 11.86 Earth years
Temperature: −108 °C (−162 °F, 165 K) at the cloud tops
Atmosphere: No solid surface. Hydrogen 89.8 percent, helium 10.2 percent, with clouds of ammonia and water.
Sunlight: 50 W/m², 3.7 percent of what Earth receives
Composition: Mostly hydrogen and helium, like the Sun. Deep inside, pressure turns the hydrogen liquid. Juno spacecraft data point to a large core partly dissolved into the liquid metal hydrogen around it.
Moons: 115 known

Jupiter has no solid surface. This view shows the top of its atmosphere.

Map: Cassini images from December 2000 (NASA/JPL/Space Science Institute).

Sources: NASA Jupiter Fact Sheet, NASA Science, Jupiter facts, NASA Jupiter Rings Fact Sheet

Sixth planet from the Sun

Saturn

Named for: Saturn, the Roman god of farming and wealth, father of Jupiter
Age: 4.5 billion years
Discovered: Recorded since ancient times. No discoverer is known. Saturn is the farthest planet visible without a telescope.
Distance from the Sun: 1,427 million km on average (9.54 AU)
Distance from Earth: 1,205.5 million to 1,658.6 million km
Diameter: 120,536 km, 9.4 times Earth's
Mass: 5.68 × 10²⁶ kg, 95 Earths
Gravity: 9.0 m/s² at the cloud tops, 92 percent of Earth's
Escape velocity: 35.5 km/s
Day: 10.66 hours
Year: 29.45 Earth years
Temperature: −139 °C (−218 °F, 134 K) at the cloud tops
Atmosphere: No solid surface. Hydrogen 96.3 percent, helium 3.25 percent, with clouds of ammonia and water.
Sunlight: 14.8 W/m², 1.1 percent of what Earth receives
Rings: Main rings (C, B and A) from 74,658 to 136,780 km from the center. The dark gap between the two brightest rings is the Cassini division.
Composition: Mostly hydrogen and helium. Dense core of iron, nickel and rock, inside layers of liquid metal hydrogen and liquid hydrogen.
Moons: 293 known

Saturn has no solid surface. This view shows the top of its atmosphere.

Within 8° of each pole, where Hubble sees the planet only at a slant, the map shows a plain tone.

Map: Hubble Space Telescope images from August 2025 and, for the band the rings hid, August 2024 (NASA, ESA, A.A. Simon, M.H. Wong and the OPAL program, CC BY 4.0). Colors come from Hubble's red, green and blue filters.

Sources: NASA Saturn Fact Sheet, NASA Saturnian Rings Fact Sheet, NASA Science, Saturn facts, NASA Science, Saturn moons

Seventh planet from the Sun

Uranus

Named for: Uranus, the Greek god of the sky, as Johann Bode proposed. William Herschel wanted Georgium Sidus, for King George III.
Age: 4.5 billion years
Discovered: March 13, 1781, by William Herschel. First planet found with a telescope.
Distance from the Sun: 2,867 million km on average (19.2 AU)
Distance from Earth: 2,580.6 million to 3,153.5 million km
Diameter: 51,118 km, 4.0 times Earth's
Mass: 8.68 × 10²⁵ kg, 14.5 Earths
Gravity: 8.7 m/s² at the cloud tops, 89 percent of Earth's
Escape velocity: 21.3 km/s
Day: 17.24 hours. Uranus rotates east to west, the reverse of Earth's direction. Its axis is tilted 97.8°, which puts the planet on its side.
Year: 84.0 Earth years
Temperature: −197 °C (−323 °F, 76 K) at the cloud tops. Down to −224 °C (−371 °F, 49 K) higher up.
Atmosphere: No solid surface. Hydrogen 82.5 percent, helium 15.2 percent, methane 2.3 percent.
Sunlight: 3.7 W/m², 0.27 percent of what Earth receives
Composition: Ice giant. Hot, dense fluid of water, methane and ammonia forms 80 percent or more of its mass, over a small rocky core.
Moons: 29 known

Uranus has no solid surface. This view shows the top of its atmosphere.

Uranus's north pole is tilted toward the Sun and Earth. South of 23° south, where Hubble sees the planet only at a slant, the map shows a plain tone.

Map: Hubble Space Telescope images from October 2025 and, south of the equator, September 2015 (NASA, ESA, A.A. Simon, M.H. Wong and the OPAL program, CC BY 4.0). Colors come from Hubble's red, green and blue filters.

Sources: NASA Uranus Fact Sheet, NASA Uranian Rings Fact Sheet, NASA Science, Uranus facts, NASA Science, Uranus moons facts

Eighth planet from the Sun

Neptune

Named for: Neptune, the Roman god of the sea. Its moons are named for lesser sea gods and nymphs of Greek myth.
Age: 4.5 billion years
Discovered: September 23, 1846, by Johann Gottfried Galle. Urbain Le Verrier predicted where it would be from the pull it put on Uranus. First planet found by calculation.
Distance from the Sun: 4,498 million km on average (30.07 AU)
Distance from Earth: 4,319 million to 4,711 million km
Diameter: 49,528 km, 3.9 times Earth's
Mass: 1.02 × 10²⁶ kg, 17.1 Earths
Gravity: 11.0 m/s² at the cloud tops, 1.12 times Earth's
Escape velocity: 23.5 km/s
Day: 16.11 hours
Year: 164.8 Earth years
Temperature: −201 °C (−330 °F, 72 K) at the cloud tops
Atmosphere: No solid surface. Hydrogen 80.0 percent, helium 19.0 percent, methane 1.5 percent.
Sunlight: 1.5 W/m², 0.11 percent of what Earth receives
Composition: Ice giant. Hot, dense fluid of water, methane and ammonia forms 80 percent or more of its mass. Its air blends into melted ices over a solid core with roughly Earth's mass.
Moons: 16 known

Neptune has no solid surface. This view shows the top of its atmosphere.

Neptune's south pole is tilted toward Earth. North of 35° north, where Hubble sees the planet only at a slant, the map shows a plain tone.

Map: Hubble Space Telescope images from August 2025 (NASA, ESA, A.A. Simon, M.H. Wong and the OPAL program, CC BY 4.0). Colors come from Hubble's red, green and blue filters.

Sources: NASA Neptune Fact Sheet, NASA Neptunian Rings Fact Sheet, NASA Science, Neptune facts

Earth's moon

Moon

Named for: Latin luna, the root of the word lunar. It shares its English name with every moon, since no other moon was known until 1610.
Discovered: Observed throughout human history.
Age: 4.5 billion years. Rock samples show it formed roughly 60 million years after the solar system began, likely after a Mars-sized body hit Earth.
Distance from Earth: 384,400 km on average, from 357,000 to 407,000 km
Diameter: 3,475 km, 27 percent of Earth's
Mass: 7.35 × 10²² kg, 1.2 percent of Earth's
Gravity: 1.62 m/s², 17 percent of Earth's
Escape velocity: 2.38 km/s
Orbit: 27.32 Earth days. 29.53 days from one new moon to the next.
Day: Same length as its orbit. One side always faces Earth.
Temperature: 117 °C (243 °F) in sunlight, −178 °C (−288 °F) in darkness, at the equator
Atmosphere: Nearly none, 3 × 10⁻¹⁵ bar at night
Composition: Solid iron-rich inner core, 240 km in radius, inside a liquid iron layer. Mantle of iron- and magnesium-rich minerals. Crust of oxygen, silicon, magnesium, iron, calcium and aluminum, 40 km thick on the near side and up to 60 km on the far side.

Map: Lunar Reconnaissance Orbiter camera images (NASA, Arizona State University), color map by NASA's Scientific Visualization Studio.

Sources: NASA Moon Fact Sheet, NASA Science, Moon facts, NASA Science, Moon formation, NASA Science, Moon composition

Moon of Mars

Phobos

Named for: Phobos, meaning fear, a son of Ares in Greek myth. Asaph Hall named both moons of Mars for sons of Ares, the Greek Mars.
Discovered: August 17, 1877, by Asaph Hall
Age: Not measured directly. Possibly a captured asteroid, or debris from the early solar system.
Distance from Mars: 9,378 km on average
Diameter: 22 km (26 × 23 × 18 km)
Mass: 1.06 × 10¹⁶ kg
Gravity: 0.006 m/s², 0.06 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 0.32 Earth days
Day: Same length as its orbit. One side always faces Mars.
Temperature: −4 °C (25 °F) in sunlight, −112 °C (−170 °F) at its coldest
Composition: Dark, carbon-rich rock, like some asteroids. Its orbit is shrinking. Within 50 million years it will crash into Mars or break up into a ring.

Map: Viking Orbiter images (NASA), USGS Astrogeology mosaic controlled by DLR, tinted to Phobos's color.

Sources: NASA Mars Fact Sheet (moons), NASA Science, Phobos, NASA Science, Mars moons, NASA Science, Mars moons facts

Moon of Mars

Deimos

Named for: Deimos, meaning dread, a son of Ares in Greek myth and brother of Phobos
Discovered: August 11, 1877, by Asaph Hall
Age: Not measured directly. Possibly a captured asteroid, or debris from the early solar system.
Distance from Mars: 23,459 km on average
Diameter: 12 km (16 × 12 × 10 km)
Mass: 2.40 × 10¹⁵ kg
Gravity: 0.004 m/s², 0.04 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 1.26 Earth days
Day: Same length as its orbit. One side always faces Mars.
Composition: Dark, carbon-rich material, like asteroids of the outer asteroid belt.

Map: Viking Orbiter images (NASA/JPL), cylindrical map by Philip Stooke with positions from Peter Thomas's shape model (Cornell University), tinted to Deimos's color.

Sources: NASA Mars Fact Sheet (moons), NASA Science, Deimos, NASA Science, Mars moons

Moon of Jupiter

Io

Named for: Io, a woman of Greek myth whom Zeus turned into a cow
Discovered: January 8, 1610, by Galileo Galilei. Io, Europa, Ganymede and Callisto were the first moons found circling another planet.
Age: 4.5 billion years, the same as the solar system. It formed from material left over after Jupiter formed.
Distance from Jupiter: 421,800 km on average
Diameter: 3,643 km
Mass: 8.93 × 10²² kg
Gravity: 1.80 m/s², 18 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 1.77 Earth days
Day: Same length as its orbit. One side always faces Jupiter.
Atmosphere: Thin, mostly sulfur dioxide
Composition: Silicate rock, probably around an iron core, with almost no water. Its volcanoes cover the surface in sulfur compounds and silicate lava, including lakes of molten lava. Its biggest eruptions show up in large telescopes on Earth.

Map: Galileo and Voyager images (NASA), USGS Astrogeology color mosaic.

Sources: NASA Jovian Satellite Fact Sheet, NASA Science, Io facts, NASA Science, Io, NASA Science, Europa facts (age of the four large moons), NASA Science, Jupiter moons

Moon of Jupiter

Europa

Named for: Europa, a woman of Greek myth abducted by Zeus
Discovered: January 1610, by Galileo Galilei. On his first night of observing, January 7, it and Io looked like a single point of light.
Age: 4.5 billion years, the same as the solar system. It formed from material left over after Jupiter formed. Its surface is only 40 to 90 million years old.
Distance from Jupiter: 671,100 km on average
Diameter: 3,122 km
Mass: 4.80 × 10²² kg
Gravity: 1.32 m/s², 13 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 3.55 Earth days
Day: Same length as its orbit. One side always faces Jupiter.
Atmosphere: Thin oxygen. Water vapor above the surface was reported in 2019.
Composition: Iron core, rocky mantle, and an ocean of salty water 60 to 150 km deep under an ice shell 15 to 25 km thick. The surface is mostly water ice, crossed by reddish-brown streaks that likely contain salts and sulfur compounds.

The area around the south pole has no usable image and shows as a plain tone.

Map: Galileo and Voyager images (NASA), USGS Astrogeology mosaic, colored by brightness in Europa's own tones.

Sources: NASA Jovian Satellite Fact Sheet, NASA Science, Europa facts, NASA Science, Jupiter moons, NASA JPL, Galileo's first telescopic view of Jupiter

Moon of Jupiter

Ganymede

Named for: Ganymede, a young man of Greek myth whom Zeus made cupbearer to the gods
Discovered: January 7, 1610, by Galileo Galilei
Age: 4.5 billion years, the same as the solar system. It formed from material left over after Jupiter formed.
Distance from Jupiter: 1,070,400 km on average
Diameter: 5,262 km
Mass: 1.48 × 10²³ kg
Gravity: 1.43 m/s², 15 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 7.15 Earth days
Day: Same length as its orbit. One side always faces Jupiter.
Temperature: −183 °C (−297 °F) to −113 °C (−171 °F) in daylight
Atmosphere: Thin oxygen
Composition: Largest moon in the solar system. Iron core, rock mantle and an ice shell, with an ocean 100 km thick under 150 km of ice. Juno found mineral salts and organic compounds on the surface.

The areas around both poles have no usable image and show as a plain tone.

Map: Galileo and Voyager images (NASA), USGS Astrogeology color mosaic.

Sources: NASA Jovian Satellite Fact Sheet, NASA Science, Ganymede facts, NASA Science, Ganymede

Moon of Jupiter

Callisto

Named for: Callisto, a woman of Greek myth whom Zeus turned into a bear
Discovered: January 7, 1610, by Galileo Galilei
Age: 4.5 billion years, the same as the solar system. It formed from material left over after Jupiter formed. Its surface is 4 billion years old.
Distance from Jupiter: 1,882,700 km on average
Diameter: 4,821 km
Mass: 1.08 × 10²³ kg
Gravity: 1.24 m/s², 13 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 16.69 Earth days
Day: Same length as its orbit. One side always faces Jupiter.
Atmosphere: Extremely thin carbon dioxide, oxygen and hydrogen
Composition: Ice mixed with rock and metal, possibly all the way to the center. Possible ocean 250 km down. Oldest, heaviest-cratered surface in the solar system.

The areas around both poles have no usable image and show as a plain tone.

Map: Galileo and Voyager images (NASA), USGS Astrogeology mosaic, tinted to Callisto's color.

Sources: NASA Jovian Satellite Fact Sheet, NASA Science, Callisto facts, NASA Science, Europa facts (age of the four large moons)

Moon of Saturn

Mimas

Named for: Mimas, a giant of Greek myth killed by Mars. John Herschel chose the name.
Discovered: September 17, 1789, by William Herschel
Age: Not measured directly. Saturn formed 4.5 billion years ago.
Distance from Saturn: 185,520 km on average
Diameter: 396 km (416 × 394 × 382 km)
Mass: 3.79 × 10¹⁹ kg
Gravity: 0.064 m/s², 0.7 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 0.94 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Composition: Nearly all water ice, the only substance ever detected on it. Cassini found signs of an ocean or a water-ice core inside.

Map: Cassini images (NASA/JPL-Caltech/Space Science Institute), tinted to Mimas's color.

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Mimas, NASA Science, Saturn moons facts, NASA Science, Saturn facts (age), NASA JPL, Planetary Satellite Physical Parameters

Moon of Saturn

Enceladus

Named for: Enceladus, a giant of Greek myth. John Herschel proposed the name in 1847.
Discovered: August 28, 1789, by William Herschel
Age: Not measured directly. Saturn formed 4.5 billion years ago.
Distance from Saturn: 238,020 km on average
Diameter: 504 km
Mass: 1.08 × 10²⁰ kg
Gravity: 0.11 m/s², 1.2 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 1.37 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Temperature: −201 °C (−330 °F, 72 K)
Atmosphere: Thin water vapor over the south pole, fed by jets that also carry carbon dioxide, methane, salts and silica.
Composition: Water ice over a global ocean of salty water. The ice is 20 to 25 km thick on average and 1 to 5 km at the south pole, where jets spray water vapor and ice into space.

Map: Cassini images (NASA/JPL/Space Science Institute), USGS Astrogeology mosaic, tinted to Enceladus's color.

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Enceladus, NASA Science, Cassini at Enceladus, NASA Science, Saturn facts (age)

Moon of Saturn

Tethys

Named for: Tethys, a Titan of Greek myth, wife of Oceanus
Discovered: March 21, 1684, by Giovanni Cassini
Age: Not measured directly. Saturn formed 4.5 billion years ago.
Distance from Saturn: 294,660 km on average
Diameter: 1,061 km
Mass: 6.18 × 10²⁰ kg
Gravity: 0.15 m/s², 1.5 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 1.89 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Temperature: −187 °C (−305 °F, 86 K) on average
Composition: Nearly all water ice with a little rock. Density 0.98 times that of water.

Map: Cassini images (NASA/JPL/Space Science Institute), USGS Astrogeology mosaic, tinted to Tethys's color.

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Tethys, NASA Science, Saturn facts (age)

Moon of Saturn

Dione

Named for: Dione, a Titan of Greek myth, mother of Aphrodite in Homer
Discovered: March 21, 1684, by Giovanni Cassini
Age: Not measured directly. Saturn formed 4.5 billion years ago.
Distance from Saturn: 377,400 km on average
Diameter: 1,123 km
Mass: 1.10 × 10²¹ kg
Gravity: 0.23 m/s², 2.4 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 2.74 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Temperature: −186 °C (−303 °F, 87 K) on average
Atmosphere: Extremely thin, one five-trillionth the density of Earth's air
Composition: One third dense core, probably silicate rock. Two thirds ice.

Map: Cassini and Voyager images (NASA/JPL), USGS Astrogeology mosaic, tinted to Dione's color.

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Dione, NASA Science, Saturn moons facts, NASA Science, Saturn facts (age)

Moon of Saturn

Rhea

Named for: Rhea, a Titan of Greek myth, mother of several Olympian gods
Discovered: December 23, 1672, by Giovanni Cassini
Age: Not measured directly. Its plains are 4 billion years old on average.
Distance from Saturn: 527,040 km on average
Diameter: 1,527 km
Mass: 2.31 × 10²¹ kg
Gravity: 0.26 m/s², 2.7 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 4.52 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Temperature: −174 °C (−281 °F) in sunlight, −220 °C (−364 °F) in shade
Atmosphere: Very thin oxygen and carbon dioxide, one five-trillionth the density of Earth's air
Composition: Three quarters ice, one quarter rock, thought to be mixed evenly.

Map: Cassini and Voyager images (NASA/JPL), USGS Astrogeology mosaic, tinted to Rhea's color.

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Rhea

Moon of Saturn

Titan

Named for: The Titans of Greek myth. John Herschel chose the name. Huygens called it Luna Saturni, Latin for Saturn's moon.
Discovered: March 25, 1655, by Christiaan Huygens
Age: Not measured directly. The nitrogen in its air suggests its building blocks formed early in the solar system's history.
Distance from Saturn: 1,221,870 km on average
Diameter: 5,150 km
Mass: 1.35 × 10²³ kg
Gravity: 1.35 m/s², 14 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 15.95 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Temperature: −179 °C (−290 °F, 94 K) at the surface
Atmosphere: 1.6 times Earth's air pressure. Nitrogen 95 percent, methane 5 percent. Reaches 600 km up.
Composition: Core of water-bearing rock, then a layer of high-pressure ice, a layer of salty water and a crust of water ice. Its dunes are dark grains of hydrocarbons.

Toward the poles, which the image shows only at the edge of Titan's disk, the globe repeats the color measured at 60°.

Map: haze colors by latitude from a Cassini natural-color image of January 2012 (NASA/JPL-Caltech/Space Science Institute). In visible light the haze hides the surface and looks much the same at every longitude.

Near 68° south, a small wedge that Cassini's camera never imaged shows as a plain tone on the surface map.

Surface map: Cassini near-infrared images, global mosaic by USGS Astrogeology (Weller, Archinal, Redding, Karkoschka and Bland, 2025).

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Titan facts

Moon of Saturn

Iapetus

Named for: Iapetus, a Titan of Greek myth, father of Atlas and Prometheus
Discovered: October 25, 1671, by Giovanni Cassini
Age: Not measured directly. Saturn formed 4.5 billion years ago.
Distance from Saturn: 3,560,850 km on average
Diameter: 1,469 km (1,492 × 1,492 × 1,424 km)
Mass: 1.81 × 10²¹ kg
Gravity: 0.22 m/s², 2.3 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 79.33 Earth days
Day: Same length as its orbit. One side always faces Saturn.
Composition: Possibly three quarters ice, one quarter rock. Density 1.1 times that of water. One half is far darker than the other.

Map: Cassini and Voyager images (NASA/JPL), USGS Astrogeology mosaic, tinted to Iapetus's color.

Sources: NASA Saturnian Satellite Fact Sheet, NASA Science, Iapetus, NASA Science, Saturn facts (age)

Moon of Uranus

Miranda

Named for: Miranda, Prospero's daughter in Shakespeare's The Tempest. The moons of Uranus are named for characters of Shakespeare and Alexander Pope.
Discovered: February 16, 1948, by Gerard P. Kuiper
Age: Not measured directly. Uranus formed 4.5 billion years ago.
Distance from Uranus: 129,900 km on average
Diameter: 471 km
Mass: 6.4 × 10¹⁹ kg
Gravity: 0.077 m/s², 0.8 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 1.41 Earth days
Day: Same length as its orbit. One side always faces Uranus.
Composition: Roughly half water ice, half rock. Carbon-rich material darkens the surface.

Voyager 2 photographed only the southern hemisphere in 1986, while the north was in darkness. The north shows as a plain tone. Sunlight now falls on the north. The photographed south stays in darkness until Uranus's next equinox, in 2049.

Map: Voyager 2 images (NASA/JPL), from NASA 3D Resources, tinted to Miranda's color.

Sources: NASA Uranian Satellite Fact Sheet, NASA Science, Miranda, NASA Science, Uranus facts, NASA JPL, Planetary Satellite Physical Parameters

Moon of Uranus

Ariel

Named for: Ariel, a spirit in Shakespeare's The Tempest and Pope's The Rape of the Lock
Discovered: October 24, 1851, by William Lassell
Age: Not measured directly. Uranus formed 4.5 billion years ago.
Distance from Uranus: 190,900 km on average
Diameter: 1,158 km
Mass: 1.25 × 10²¹ kg
Gravity: 0.25 m/s², 2.5 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 2.52 Earth days
Day: Same length as its orbit. One side always faces Uranus.
Composition: Roughly half water ice, half rock. Carbon dioxide detected. Brightest of the larger moons of Uranus.

Map: Voyager 2 images (NASA/JPL), from NASA 3D Resources, tinted to Ariel's color.

Sources: NASA Uranian Satellite Fact Sheet, NASA Science, Ariel, NASA Science, Miranda, NASA Science, Uranus facts (age), NASA JPL, Planetary Satellite Physical Parameters

Moon of Uranus

Umbriel

Named for: Umbriel, a malevolent spirit in Alexander Pope's The Rape of the Lock
Discovered: October 24, 1851, by William Lassell
Age: Not measured directly. Uranus formed 4.5 billion years ago.
Distance from Uranus: 266,000 km on average
Diameter: 1,169 km
Mass: 1.28 × 10²¹ kg
Gravity: 0.25 m/s², 2.5 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 4.14 Earth days
Day: Same length as its orbit. One side always faces Uranus.
Composition: Roughly half water ice, half rock.

Map: Voyager 2 images (NASA/JPL), from NASA 3D Resources, tinted to Umbriel's color.

Sources: NASA Uranian Satellite Fact Sheet, NASA Science, Umbriel, NASA Science, Uranus moons facts, NASA Science, Uranus facts (age), NASA JPL, Planetary Satellite Physical Parameters

Moon of Uranus

Titania

Named for: Titania, queen of the fairies in Shakespeare's A Midsummer Night's Dream
Discovered: January 11, 1787, by William Herschel, together with Oberon
Age: Not measured directly. Uranus formed 4.5 billion years ago.
Distance from Uranus: 436,300 km on average
Diameter: 1,578 km
Mass: 3.42 × 10²¹ kg
Gravity: 0.37 m/s², 3.7 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 8.71 Earth days
Day: Same length as its orbit. One side always faces Uranus.
Composition: Roughly half water ice, half rock. Largest moon of Uranus.

Map: Voyager 2 images (NASA/JPL), from NASA 3D Resources, tinted to Titania's color.

Sources: NASA Uranian Satellite Fact Sheet, NASA Science, Titania, NASA Science, Uranus moons facts, NASA Science, Uranus facts (age)

Moon of Uranus

Oberon

Named for: Oberon, king of the fairies in Shakespeare's A Midsummer Night's Dream
Discovered: January 11, 1787, by William Herschel, together with Titania
Age: Not measured directly. Uranus formed 4.5 billion years ago.
Distance from Uranus: 583,500 km on average
Diameter: 1,523 km
Mass: 3.08 × 10²¹ kg
Gravity: 0.35 m/s², 3.6 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 13.46 Earth days
Day: Same length as its orbit. One side always faces Uranus.
Composition: Roughly half water ice, half rock.

Map: Voyager 2 images (NASA/JPL), from NASA 3D Resources, tinted to Oberon's color.

Sources: NASA Uranian Satellite Fact Sheet, NASA Science, Oberon, NASA Science, Uranus facts (age), NASA JPL, Planetary Satellite Physical Parameters

Moon of Neptune

Triton

Named for: Triton, son of Poseidon, the Greek Neptune
Discovered: October 10, 1846, by William Lassell, 17 days after Neptune was found
Age: Not measured directly. Likely a body from the Kuiper Belt that Neptune captured millions of years ago.
Distance from Neptune: 354,760 km on average
Diameter: 2,707 km
Mass: 2.14 × 10²² kg
Gravity: 0.78 m/s², 7.9 percent of Earth's. Calculated from NASA's mass and radius.
Orbit: 5.88 Earth days
Day: Same length as its orbit. One side always faces Neptune.
Temperature: −235 °C (−391 °F, 38 K), measured by Voyager 2
Atmosphere: Thin, mostly nitrogen with a little methane
Composition: Frozen nitrogen crust over an icy mantle and a core of rock and metal. Twice the density of water. Its nitrogen frost reflects 70 percent of the sunlight that hits it. Only large moon that orbits in the opposite direction to its planet's rotation.

Voyager 2 photographed the southern hemisphere in 1989, while much of the north was in darkness. The unseen north shows as a plain tone.

Map: Voyager 2 images (NASA/JPL), color mosaic by Paul Schenk, published by USGS Astrogeology.

Sources: NASA Neptunian Satellite Fact Sheet, NASA Science, Triton, NASA Science, Neptune facts

The galaxy that contains the solar system

Milky Way

Type: Barred spiral galaxy
Size: 100,000 light-years across
The Sun's place: On the Orion Arm, halfway from the center to the edge, 8 kiloparsecs (26,000 light-years) from the center
Orbit: The solar system takes 240 million years to orbit the center of the galaxy once.

Sources: NASA Science, Galaxies, NASA Imagine the Universe, the Milky Way

Nearest major galaxy to the Milky Way

Andromeda Galaxy

Type: Spiral galaxy
Distance from Earth: 2.5 million light-years
Constellation: Andromeda
Visibility: Visible without a telescope from a dark site. Apparent magnitude 3.1.
Future: Andromeda and the Milky Way have about an even chance of colliding within the next 10 billion years.

Sources: NASA Science, Messier 31, NASA Science, Messier 33, ESA/Hubble, Hubble casts doubt on certainty of galactic collision (2025)

Third-largest galaxy in the Local Group

Triangulum Galaxy

Type: Spiral galaxy, half the size of the Milky Way
Distance from Earth: 3 million light-years
Constellation: Triangulum
Discovered: Charles Messier cataloged it in August 1764.
Visibility: Apparent magnitude 5.7. Visible without a telescope only under exceptionally clear, dark skies.
Future: If Andromeda and the Milky Way merge, Triangulum could be drawn in. Current estimates give that merger about even odds within 10 billion years.

Sources: NASA Science, Messier 33, ESA/Hubble, Hubble casts doubt on certainty of galactic collision (2025)

Dwarf galaxy orbiting the Milky Way

Large Magellanic Cloud

Type: Irregular dwarf galaxy
Distance: 162,000 light-years from Earth
Discovered: Known to southern observers since ancient times. Magellan's voyage around the world in 1519 brought it to European knowledge.
Visibility: Clearly visible without a telescope in the Southern Hemisphere sky
Contents: Nebulae, globular and open star clusters, and planetary nebulae

Sources: NASA Imagine the Universe, the Magellanic Clouds, Pietrzyński et al., A distance to the Large Magellanic Cloud that is precise to one per cent, Nature (2019)

Dwarf galaxy orbiting the Milky Way

Small Magellanic Cloud

Type: Irregular dwarf galaxy, possibly a barred disk distorted by the pull of the Milky Way and the Large Magellanic Cloud
Distance: 204,000 light-years from Earth
Discovered: Known to southern observers since ancient times. Magellan's voyage around the world in 1519 brought it to European knowledge.
Visibility: Clearly visible without a telescope in the Southern Hemisphere sky

Sources: NASA Imagine the Universe, the Magellanic Clouds, Graczyk et al., A distance determination to the Small Magellanic Cloud, The Astrophysical Journal (2020)

Closest large star-forming region to Earth

Orion Nebula

Type: Nebula, a cloud of gas and dust where stars form
Distance from Earth: 1,350 light-years
Constellation: Orion, just below Orion's Belt
Visibility: Visible without a telescope. Apparent magnitude 4.0.
Center: Four massive young stars light its bright center. Their ultraviolet light is carving a cavity in the nebula.

Sources: NASA Science, Messier 42, Menten et al., The distance to the Orion Nebula, Astronomy & Astrophysics (2007)

Open star cluster, also called the Seven Sisters

Pleiades

Type: Open star cluster, more than 1,000 stars loosely bound by gravity
Distance from Earth: 445 light-years. Astronomers have not settled on the exact figure.
Constellation: Taurus
Discovered: Observed since ancient times. No discoverer is known. Galileo was the first to observe it through a telescope.
Visibility: Easily visible without a telescope. Apparent magnitude 1.6.

Sources: NASA Science, Messier 45

Globular cluster of 10 million stars

Omega Centauri

Type: Globular cluster, a dense ball of stars bound by gravity
Distance from Earth: 17,000 light-years
Size: 150 light-years across
Stars: Roughly 10 million
Constellation: Centaurus
Discovered: Ptolemy recorded it as a star. Edmond Halley listed it as a nebulous object in 1677. John Herschel identified it as a star cluster in 1836.
Visibility: Visible without a telescope. Apparent magnitude 3.7.
Center: Hubble and ground-based telescopes indicate a black hole at its center.

Sources: NASA Science, Caldwell 80, ESO, eso0844, Omega Centauri

Globular cluster in Hercules

Hercules Cluster

Type: Globular cluster
Distance from Earth: 25,000 light-years
Stars: More than 100,000
Constellation: Hercules
Discovered: Edmond Halley, 1714
Visibility: Apparent magnitude 5.8. Visible with binoculars, best seen in July.

Sources: NASA Science, Messier 13

Star-forming cloud in Sagittarius

Lagoon Nebula

Type: Emission nebula, glowing from the ultraviolet light of the young stars inside it
Distance from Earth: 4,300 light-years
Constellation: Sagittarius
Discovered: Giovanni Battista Hodierna, 1654
Visibility: Apparent magnitude 6. Faintly visible without a telescope in dark skies.
Stars: Contains the star cluster NGC 6530, several thousand stars

Sources: NASA Science, Messier 8, Damiani et al., A Gaia DR2 study of the young cluster NGC 6530, Astronomy & Astrophysics (2019)

Star-forming nebula in the Milky Way

Carina Nebula

Type: Emission nebula
Distance from Earth: 7,500 light-years
Size: 300 light-years across
Constellation: Carina
Discovered: Nicolas-Louis de Lacaille, 1752, from the Cape of Good Hope
Visibility: Visible without a telescope from the Southern Hemisphere.
Star formation: Stellar winds and ultraviolet radiation inside it compress the surrounding hydrogen and trigger new star formation.

Sources: NASA Science, Caldwell 92

The Sun, the eight planets, their major moons and the asteroid belt, with NASA's measurements for each. Every study at the center builds on these figures.

Sizes and distances on the map are compressed so every world fits on screen. The figures in this panel are the measured values.

The planets appear where they are in their orbits today, calculated from NASA's orbital elements. One AU, the average distance from Earth to the Sun, is 149.6 million km.

The stars behind the map are the 41,411 stars brighter than magnitude 8 in the European Space Agency's Hipparcos Catalogue, at their true positions in the sky, along with nearby galaxies, star clusters and nebulae.

Scroll or pinch to zoom. Select any world to see its measurements.