Characteristics of Celestial Bodies

Mean orbital velocity indicates the average speed at which a planet orbits the Sun unless otherwise specified. Inclination of orbit to ecliptic indicates the angle of tilt between a planet’s orbit and the plane of Earth’s orbit (essentially the plane of the solar system). Orbital period indicates the planet’s sidereal year (in Earth days except where noted). Rotation period indicates the planet’s sidereal day (in Earth days except where noted). Inclination of equator to orbit indicates the angle of tilt between a planet’s orbit and its equator. Gravitational acceleration is a measure of the body’s gravitational pull on other objects. Escape velocity is the speed needed at the surface to escape the planet’s gravitational pull. Eccentricity of orbit is a measure of the circularity or elongation of an orbit; 0 indicates circular orbits, and closer to 1 more elliptical ones.

Sun

Sun

diameter (at equator): 1.39 million km (863,705 mi)

mass (in 1020 kg): 19.8 billion

density (mass/volume, in kg/m3): 1,408

mean orbital velocity: the Sun orbits the Milky Way’s

center at around 220 km/sec (136.7 mi/sec)

orbital period: the Sun takes approximately 250 millionEarth years to complete its orbit around the Milky Way’s center

rotation period: 25–36 Earth days

gravitational acceleration: 275 m/sec2 (902.2 ft/sec2)

escape velocity: 618.02 km/sec (384.01 mi/sec)

mean temperature at visible surface: 5,527 °C (9,980 °F)

probes and space missions: US—Pioneer 5–9,

launched 1960–68; Skylab, 1973; Genesis,

2001; Japan—Yohkoh, 1991; US/European Space

Agency (ESA)—Ulysses, 1990; SOHO, 1995.

mass (in 1020 kg): 19.8 billion

density (mass/volume, in kg/m3): 1,408

mean orbital velocity: the Sun orbits the Milky Way’s

center at around 220 km/sec (136.7 mi/sec)

orbital period: the Sun takes approximately 250 millionEarth years to complete its orbit around the Milky Way’s center

rotation period: 25–36 Earth days

gravitational acceleration: 275 m/sec2 (902.2 ft/sec2)

escape velocity: 618.02 km/sec (384.01 mi/sec)

mean temperature at visible surface: 5,527 °C (9,980 °F)

probes and space missions: US—Pioneer 5–9,

launched 1960–68; Skylab, 1973; Genesis,

2001; Japan—Yohkoh, 1991; US/European Space

Agency (ESA)—Ulysses, 1990; SOHO, 1995.

Mercury

average distance from the Sun: 58 million km (36

million mi)

diameter (at equator): 4,879 km (3,032 mi)

mass (in 1020 kg): 3,300

density (mass/volume, in kg/m3): 5,427

eccentricity of orbit: 0.206

mean orbital velocity: 47.9 km/sec (29.7 mi/sec)

inclination of orbit to ecliptic: 7.0°

orbital period: 88 Earth days

rotation period: 58.6 Earth days

inclination of equator to orbit: probably 0°

gravitational acceleration: 3.7 m/sec2 (12.1 ft/sec2)

escape velocity: 4.3 km/sec (2.7 mi/sec)

mean temperature at surface†: 167 °C (333 °F)

satellites: none known

probes and space missions: US—Mariner 10, 1973;

Messenger, 2004.

Venus

average distance from the Sun: 108.2 million km

(67.2 million mi)

diameter (at equator): 12,104 km (7,521 mi)

mass (in 1020 kg): 48,700

density (mass/volume, in kg/m3): 5,243

eccentricity of orbit: 0.007

mean orbital velocity: 35.0 km/sec (21.8 mi/sec)

inclination of orbit to ecliptic: 3.4°

orbital period: 224.7 Earth days

rotation period: 243.0 Earth days (retrograde)

inclination of equator to orbit: 177.4°

gravitational acceleration: 8.9 m/sec2 (29.1 ft/sec2)

escape velocity: 10.4 km/sec (6.4 mi/sec)

mean temperature at surface†: 464 °C (867 °F)

satellites: none known

probes and space missions: USSR—Venera 1–16,

1961–83; Vega 1 and 2, 1984; US—Mariner 2, 5,

and 10, 1962, 1967, and 1973; Pioneer Venus Orbiter

and Pioneer Venus Multiprobe, 1978; Galileo,

1989; Magellan, 1989; ESA—Venus Express, 2005.

Earth

average distance from the Sun: 149.6 million km (93

million mi)

diameter (at equator): 12,756 km (7,926 mi)

mass (in 1020 kg): 59,700

density (mass/volume, in kg/m3): 5,515

eccentricity of orbit: 0.017

mean orbital velocity: 29.8 km/sec (18.5 mi/sec)

inclination of orbit to ecliptic: 0.00°

orbital period: 365.25 days

rotation period: 23 hours, 56 minutes, and 4

seconds of mean solar time

inclination of equator to orbit: 23.5°

gravitational acceleration: 9.8 m/sec2 (32.1 ft/sec2)

escape velocity: 11.2 km/sec (7.0 mi/sec)

mean temperature at surface†: 15 °C (59 °F)

satellites: 1 known—the Moon.

Moon (of Earth)

average distance from Earth: 384,401 km

(238,855.7 mi)

diameter (at equator): 3,475 km (2,159 mi)

mass (in 1020 kg): 730

density (mass/volume, in kg/m3): 3,340

eccentricity of orbit: orbital eccentricity of Moon

around Earth is 0.055

mean orbital velocity: the Moon orbits Earth at 1.0

km/sec (0.64 mi/sec)

inclination of orbit to ecliptic: 5.1°

orbital period: the Moon revolves around Earth in

27.32 Earth days

rotation period: the Moon rotates on its axis every

27.32 Earth days (synchronous with orbital period)

inclination of equator to orbit: 6.7°

gravitational acceleration: 1.6 m/sec2 (5.3 ft/sec2)

escape velocity: 2.4 km/sec (1.5 mi/sec)

mean temperature at surface†: daytime: 107 °C

(224.6 °F); nighttime: −153 °C (−243.4 °F)

probes and space missions: USSR, US, ESA, Japan—

collectively about 70 missions since 1959, including

9 manned missions by the US. On 20 Jul 1969

humans first set foot on the Moon, from NASA’s

Apollo 11.

Mars

average distance from the Sun: 227.9 million km

(141.6 million mi)

diameter (at equator): 6,794 km (4,222 mi)

mass (in 1020 kg): 6,420

density (mass/volume, in kg/m3): 3,933

eccentricity of orbit: 0.094

mean orbital velocity: 24.1 km/sec (15 mi/sec)

inclination of orbit to ecliptic: 1.9°

orbital period: 687 Earth days (1.88 Earth years)

rotation period: 24.6 Earth hours

inclination of equator to orbit: 24.9°

gravitational acceleration: 3.7 m/sec2 (12.1 ft/sec2)

escape velocity: 5.0 km/sec (3.1 mi/sec)

mean temperature at surface†: −65 °C (−85 °F)

satellites: 2 known—Phobos and Deimos

probes and space missions: US—Mariner 4, 6, 7, and

9, 1964–71; Viking 1 and 2, 1975; Mars Global

Surveyor, 1996; Mars Pathfinder, 1996; 2001

Mars Odyssey, 2001; Mars Exploration Rovers,

2003; Mars Reconnaissance Orbiter, 2005; USSR—

Mars 2–7, 1971–73; Phobos 1 and 2, 1988; ESA—

Mars Express, 2003; Phoenix, 2007.

Jupiter

average distance from the Sun: 778.6 million km

(483.8 million mi)

diameter (at equator): 142,984 km (88,846 mi)

mass (in 1020 kg): 18.99 million

density (mass/volume, in kg/m3): 1,326

eccentricity of orbit: 0.049

mean orbital velocity: 13.1 km/sec (8.1 mi/sec)

inclination of orbit to ecliptic: 1.3°

orbital period: 11.86 Earth years

rotation period: 9.9 Earth hours

inclination of equator to orbit: 3.1°

gravitational acceleration: 23.1 m/sec2 (75.9 ft/sec2)

escape velocity: 59.5 km/sec (37.0 mi/sec)

mean temperature at surface†: −110 °C (−166 °F)

satellites: at least 62 moons—including Callisto,

Ganymede, Europa, and Io—plus rings

probes and space missions: US—Pioneer 10 and

11, 1972–73; Voyager 1 and 2, 1977; Galileo,

1989; Ulysses, 1990; US/ESA—Cassini-Huygens,

1997.

Saturn

average distance from the Sun: 1.433 billion km

(890.8 million mi)

diameter (at equator): 120,536 km (74,897 mi)

mass (in 1020 kg): 5.68 million

density (mass/volume, in kg/m3): 687

eccentricity of orbit: 0.057

mean orbital velocity: 9.7 km/sec (6 mi/sec)

inclination of orbit to ecliptic: 2.5°

orbital period: 29.43 Earth years

rotation period: 10.66 Earth hours

inclination of equator to orbit: 26.7°

gravitational acceleration: 9.0 m/sec2 (29.4 ft/sec2)

escape velocity: 35.5 km/sec (22.1 mi/sec)

mean temperature at surface†: −140 °C (−220 °F)

satellites: at least 61 moons—including Titan—plus

rings

probes and space missions: US—Pioneer 11, 1973;

Voyager 1 and 2, 1977; US/ESA—Cassini/Huygens,

1997.

Uranus

average distance from the Sun: 2.872 billion km

(1.784 billion miles)

diameter (at equator): 51,118 km (31,763 mi)

mass (in 1020 kg): 868,000

density (mass/volume, in kg/m3): 1,270

eccentricity of orbit: 0.046

mean orbital velocity: 6.8 km/sec (4.2 mi/sec)

inclination of orbit to ecliptic: 0.8°

orbital period: 84.01 Earth years

rotation period: 17.2 Earth hours (retrograde)

inclination of equator to orbit: 97.8°

gravitational acceleration: 8.7 m/sec2 (28.5 ft/sec2)

escape velocity: 21.3 km/sec ( 13.2 mi/sec)

mean temperature at surface†: −195 °C (−320 °F)

satellites: at least 27 moons, plus rings

probes and space missions: US—Voyager 2, 1977.

Neptune

average distance from the Sun: 4.495 billion km

(2.793 billion mi)

diameter (at equator): 49,528 km (30,775 mi)

mass (in 1020 kg): 1.02 million

density (mass/volume, in kg/m3): 1,638

eccentricity of orbit: 0.009

mean orbital velocity: 5.48 km/sec (3.40 mi/sec)

inclination of orbit to ecliptic: 1.8°

orbital period: 164.79 Earth years

rotation period: 16.1 Earth hours

inclination of equator to orbit: 28.3°

gravitational acceleration: 11.0 m/sec2 (36.0

ft/sec2)

escape velocity: 23.5 km/sec (14.6 mi/sec)

mean temperature at surface†: −200 °C (−330 °F)

satellites: at least 13 moons, plus rings

probes and space missions: US—Voyager 2, 1977.

average distance from the Sun: 58 million km (36

million mi)

diameter (at equator): 4,879 km (3,032 mi)

mass (in 1020 kg): 3,300

density (mass/volume, in kg/m3): 5,427

eccentricity of orbit: 0.206

mean orbital velocity: 47.9 km/sec (29.7 mi/sec)

inclination of orbit to ecliptic: 7.0°

orbital period: 88 Earth days

rotation period: 58.6 Earth days

inclination of equator to orbit: probably 0°

gravitational acceleration: 3.7 m/sec2 (12.1 ft/sec2)

escape velocity: 4.3 km/sec (2.7 mi/sec)

mean temperature at surface†: 167 °C (333 °F)

satellites: none known

probes and space missions: US—Mariner 10, 1973;

Messenger, 2004.

Venus

average distance from the Sun: 108.2 million km

(67.2 million mi)

diameter (at equator): 12,104 km (7,521 mi)

mass (in 1020 kg): 48,700

density (mass/volume, in kg/m3): 5,243

eccentricity of orbit: 0.007

mean orbital velocity: 35.0 km/sec (21.8 mi/sec)

inclination of orbit to ecliptic: 3.4°

orbital period: 224.7 Earth days

rotation period: 243.0 Earth days (retrograde)

inclination of equator to orbit: 177.4°

gravitational acceleration: 8.9 m/sec2 (29.1 ft/sec2)

escape velocity: 10.4 km/sec (6.4 mi/sec)

mean temperature at surface†: 464 °C (867 °F)

satellites: none known

probes and space missions: USSR—Venera 1–16,

1961–83; Vega 1 and 2, 1984; US—Mariner 2, 5,

and 10, 1962, 1967, and 1973; Pioneer Venus Orbiter

and Pioneer Venus Multiprobe, 1978; Galileo,

1989; Magellan, 1989; ESA—Venus Express, 2005.

Earth

average distance from the Sun: 149.6 million km (93

million mi)

diameter (at equator): 12,756 km (7,926 mi)

mass (in 1020 kg): 59,700

density (mass/volume, in kg/m3): 5,515

eccentricity of orbit: 0.017

mean orbital velocity: 29.8 km/sec (18.5 mi/sec)

inclination of orbit to ecliptic: 0.00°

orbital period: 365.25 days

rotation period: 23 hours, 56 minutes, and 4

seconds of mean solar time

inclination of equator to orbit: 23.5°

gravitational acceleration: 9.8 m/sec2 (32.1 ft/sec2)

escape velocity: 11.2 km/sec (7.0 mi/sec)

mean temperature at surface†: 15 °C (59 °F)

satellites: 1 known—the Moon.

Moon (of Earth)

average distance from Earth: 384,401 km

(238,855.7 mi)

diameter (at equator): 3,475 km (2,159 mi)

mass (in 1020 kg): 730

density (mass/volume, in kg/m3): 3,340

eccentricity of orbit: orbital eccentricity of Moon

around Earth is 0.055

mean orbital velocity: the Moon orbits Earth at 1.0

km/sec (0.64 mi/sec)

inclination of orbit to ecliptic: 5.1°

orbital period: the Moon revolves around Earth in

27.32 Earth days

rotation period: the Moon rotates on its axis every

27.32 Earth days (synchronous with orbital period)

inclination of equator to orbit: 6.7°

gravitational acceleration: 1.6 m/sec2 (5.3 ft/sec2)

escape velocity: 2.4 km/sec (1.5 mi/sec)

mean temperature at surface†: daytime: 107 °C

(224.6 °F); nighttime: −153 °C (−243.4 °F)

probes and space missions: USSR, US, ESA, Japan—

collectively about 70 missions since 1959, including

9 manned missions by the US. On 20 Jul 1969

humans first set foot on the Moon, from NASA’s

Apollo 11.

Mars

average distance from the Sun: 227.9 million km

(141.6 million mi)

diameter (at equator): 6,794 km (4,222 mi)

mass (in 1020 kg): 6,420

density (mass/volume, in kg/m3): 3,933

eccentricity of orbit: 0.094

mean orbital velocity: 24.1 km/sec (15 mi/sec)

inclination of orbit to ecliptic: 1.9°

orbital period: 687 Earth days (1.88 Earth years)

rotation period: 24.6 Earth hours

inclination of equator to orbit: 24.9°

gravitational acceleration: 3.7 m/sec2 (12.1 ft/sec2)

escape velocity: 5.0 km/sec (3.1 mi/sec)

mean temperature at surface†: −65 °C (−85 °F)

satellites: 2 known—Phobos and Deimos

probes and space missions: US—Mariner 4, 6, 7, and

9, 1964–71; Viking 1 and 2, 1975; Mars Global

Surveyor, 1996; Mars Pathfinder, 1996; 2001

Mars Odyssey, 2001; Mars Exploration Rovers,

2003; Mars Reconnaissance Orbiter, 2005; USSR—

Mars 2–7, 1971–73; Phobos 1 and 2, 1988; ESA—

Mars Express, 2003; Phoenix, 2007.

Jupiter

average distance from the Sun: 778.6 million km

(483.8 million mi)

diameter (at equator): 142,984 km (88,846 mi)

mass (in 1020 kg): 18.99 million

density (mass/volume, in kg/m3): 1,326

eccentricity of orbit: 0.049

mean orbital velocity: 13.1 km/sec (8.1 mi/sec)

inclination of orbit to ecliptic: 1.3°

orbital period: 11.86 Earth years

rotation period: 9.9 Earth hours

inclination of equator to orbit: 3.1°

gravitational acceleration: 23.1 m/sec2 (75.9 ft/sec2)

escape velocity: 59.5 km/sec (37.0 mi/sec)

mean temperature at surface†: −110 °C (−166 °F)

satellites: at least 62 moons—including Callisto,

Ganymede, Europa, and Io—plus rings

probes and space missions: US—Pioneer 10 and

11, 1972–73; Voyager 1 and 2, 1977; Galileo,

1989; Ulysses, 1990; US/ESA—Cassini-Huygens,

1997.

Saturn

average distance from the Sun: 1.433 billion km

(890.8 million mi)

diameter (at equator): 120,536 km (74,897 mi)

mass (in 1020 kg): 5.68 million

density (mass/volume, in kg/m3): 687

eccentricity of orbit: 0.057

mean orbital velocity: 9.7 km/sec (6 mi/sec)

inclination of orbit to ecliptic: 2.5°

orbital period: 29.43 Earth years

rotation period: 10.66 Earth hours

inclination of equator to orbit: 26.7°

gravitational acceleration: 9.0 m/sec2 (29.4 ft/sec2)

escape velocity: 35.5 km/sec (22.1 mi/sec)

mean temperature at surface†: −140 °C (−220 °F)

satellites: at least 61 moons—including Titan—plus

rings

probes and space missions: US—Pioneer 11, 1973;

Voyager 1 and 2, 1977; US/ESA—Cassini/Huygens,

1997.

Uranus

average distance from the Sun: 2.872 billion km

(1.784 billion miles)

diameter (at equator): 51,118 km (31,763 mi)

mass (in 1020 kg): 868,000

density (mass/volume, in kg/m3): 1,270

eccentricity of orbit: 0.046

mean orbital velocity: 6.8 km/sec (4.2 mi/sec)

inclination of orbit to ecliptic: 0.8°

orbital period: 84.01 Earth years

rotation period: 17.2 Earth hours (retrograde)

inclination of equator to orbit: 97.8°

gravitational acceleration: 8.7 m/sec2 (28.5 ft/sec2)

escape velocity: 21.3 km/sec ( 13.2 mi/sec)

mean temperature at surface†: −195 °C (−320 °F)

satellites: at least 27 moons, plus rings

probes and space missions: US—Voyager 2, 1977.

Neptune

average distance from the Sun: 4.495 billion km

(2.793 billion mi)

diameter (at equator): 49,528 km (30,775 mi)

mass (in 1020 kg): 1.02 million

density (mass/volume, in kg/m3): 1,638

eccentricity of orbit: 0.009

mean orbital velocity: 5.48 km/sec (3.40 mi/sec)

inclination of orbit to ecliptic: 1.8°

orbital period: 164.79 Earth years

rotation period: 16.1 Earth hours

inclination of equator to orbit: 28.3°

gravitational acceleration: 11.0 m/sec2 (36.0

ft/sec2)

escape velocity: 23.5 km/sec (14.6 mi/sec)

mean temperature at surface†: −200 °C (−330 °F)

satellites: at least 13 moons, plus rings

probes and space missions: US—Voyager 2, 1977.

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