Celestial Bodies Characteristics

Sundiameter (at equator): 1.39 million km (863,705 mi)mass (in 1020 kg): 19.8 billiondensity (mass/volume, in kg/m3): 1,408mean orbital velocity: the Sun orbits the Milky Way’scenter at around 220 km/sec (136.7 mi/sec)orbital period: the Sun takes approximately 250 millionEarth years to complete its orbit around theMilky Way’s centerrotation period: 25–36 Earth daysgravitational acceleration: 275 m/sec2 (902.2ft/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 SpaceAgency (ESA)—Ulysses, 1990; SOHO, 1995.
Mercuryaverage distance from the Sun: 58 million km (36million mi)diameter (at equator): 4,879 km (3,032 mi)mass (in 1020 kg): 3,300density (mass/volume, in kg/m3): 5,427eccentricity of orbit: 0.206mean orbital velocity: 47.9 km/sec (29.7 mi/sec)inclination of orbit to ecliptic: 7.0°orbital period: 88 Earth daysrotation period: 58.6 Earth daysinclination 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 knownprobes and space missions: US—Mariner 10, 1973;Messenger, 2004.
Venusaverage 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): 48,700density (mass/volume, in kg/m3): 5,243eccentricity of orbit: 0.007mean orbital velocity: 35.0 km/sec (21.8 mi/sec)inclination of orbit to ecliptic: 3.4°orbital period: 224.7 Earth daysrotation 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 knownprobes 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 Orbiterand Pioneer Venus Multiprobe, 1978; Galileo,1989; Magellan, 1989; ESA—Venus Express, 2005.
Earthaverage distance from the Sun: 149.6 million km (93million mi)diameter (at equator): 12,756 km (7,926 mi)mass (in 1020 kg): 59,700density (mass/volume, in kg/m3): 5,515eccentricity of orbit: 0.017mean orbital velocity: 29.8 km/sec (18.5 mi/sec)inclination of orbit to ecliptic: 0.00°orbital period: 365.25 daysrotation period: 23 hours, 56 minutes, and 4seconds of mean solar timeinclination 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): 730density (mass/volume, in kg/m3): 3,340eccentricity of orbit: orbital eccentricity of Moonaround Earth is 0.055mean orbital velocity: the Moon orbits Earth at 1.0km/sec (0.64 mi/sec)inclination of orbit to ecliptic: 5.1°orbital period: the Moon revolves around Earth in27.32 Earth daysrotation period: the Moon rotates on its axis every27.32 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, including9 manned missions by the US. On 20 Jul 1969humans first set foot on the Moon, from NASA’sApollo 11.

Marsaverage 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): 6,420density (mass/volume, in kg/m3): 3,933eccentricity of orbit: 0.094mean 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 hoursinclination 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 Deimosprobes and space missions: US—Mariner 4, 6, 7, and9, 1964–71; Viking 1 and 2, 1975; Mars GlobalSurveyor, 1996; Mars Pathfinder, 1996; 2001Mars 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.
Marsaverage 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): 6,420density (mass/volume, in kg/m3): 3,933eccentricity of orbit: 0.094mean 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 hoursinclination 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 Deimosprobes and space missions: US—Mariner 4, 6, 7, and9, 1964–71; Viking 1 and 2, 1975; Mars GlobalSurveyor, 1996; Mars Pathfinder, 1996; 2001Mars 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.
Saturnaverage 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 milliondensity (mass/volume, in kg/m3): 687eccentricity of orbit: 0.057mean orbital velocity: 9.7 km/sec (6 mi/sec)inclination of orbit to ecliptic: 2.5°orbital period: 29.43 Earth yearsrotation period: 10.66 Earth hoursinclination 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—plusringsprobes and space missions: US—Pioneer 11, 1973;Voyager 1 and 2, 1977; US/ESA—Cassini/Huygens,1997.
Uranusaverage 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): 868,000density (mass/volume, in kg/m3): 1,270eccentricity of orbit: 0.046mean orbital velocity: 6.8 km/sec (4.2 mi/sec)inclination of orbit to ecliptic: 0.8°orbital period: 84.01 Earth yearsrotation 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 ringsprobes and space missions: US—Voyager 2, 1977.

Neptuneaverage 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 milliondensity (mass/volume, in kg/m3): 1,638eccentricity of orbit: 0.009mean orbital velocity: 5.48 km/sec (3.40 mi/sec)inclination of orbit to ecliptic: 1.8°orbital period: 164.79 Earth yearsrotation period: 16.1 Earth hoursinclination of equator to orbit: 28.3°gravitational acceleration: 11.0 m/sec2 (36.0ft/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 ringsprobes and space missions: US—Voyager 2, 1977.

Plutoaverage distance from the Sun: 5.910 billion km(3.67 billion mi); Pluto lies within the Kuiper beltand can be considered its largest known memberdiameter (at equator): 2,344 km (1,485 mi)mass (in 1020 kg): 125density (mass/volume, in kg/m3): about 2,000eccentricity of orbit: 0.249mean orbital velocity: 4.72 km/sec (2.93 mi/sec)inclination of orbit to ecliptic: 17.2°orbital period: 248 Earth yearsrotation period: 6.4 Earth days (retrograde)inclination of equator to orbit: 122.5°gravitational acceleration: 0.6 m/sec2 (1.9 ft/sec2)escape velocity: 1.1 km/sec (0.7 mi/sec)mean temperature at surface†: −225 °C (−375 °F)satellites: 3 known—including Charonprobes and space missions: US—New Horizons, 2006.

asteroids(several hundred thousand small rocky bodies, about1,000 km [610 mi] or less in diameter, that orbitthe Sun primarily between the orbits of Mars andJupiter)distance from the Sun: between approximately 300million km (190 million mi) and 600 million km(380 million mi), with notable outliersestimated mass (in 1021 kg): 2.3probes and space missions: US—Galileo, 1989;Ulysses, 1990; NEAR Shoemaker, 1996; DeepSpace 1, 1998; Stardust, 1999; Dawn, 2007;US/ESA—Cassini-Huygens, 1997; Japan—Hayabusa,2003; ESA—Rosetta, 2004.

Comet 1P/Halleydistance from the Sun at closest point of orbit: 87.8million km (54 million mi); farthest distance fromthe Sun: 5.2 billion km (3.2 billion mi).diameter (at equator): 16 x 8 x 8 km(9.9 x 4.9 x 4.9 mi)density (mass/volume, in kg/m3): possibly as lowas 200eccentricity of orbit: 0.967inclination of orbit to ecliptic: 18°orbital period: 76.1 to 79.3 Earth years; the next appearancewill be 2061. The comet’s orbit is retrograde.rotation period: 52 Earth hoursprobes and space missions: USSR—Vega 1 and 2,1984; ESA—Giotto, 1985; Japan—Sakigake and Suisei,1985.

Comet Hale-Boppdistance from the Sun at closest point of orbit: 136million km (84.5 million mi); farthest distance fromthe Sun: 74.7 billion km (46.4 billion mi).eccentricity of orbit: 0.995orbital period: 4,000 Earth years; last closest pass ofSun was on 31 Mar 1997.

Kuiper belt(a huge flat ring located beyond Neptune containingresidual icy material from the formation of the outerplanets)average distance from the Sun (main concentration):4.5–7.5 billion km (2.8–4.7 billion mi)mass: scientists estimate there may be as many as100,000 icy, cometlike bodies of a size greaterthan 100 km in the Kuiper belt; the belt is estimatedto have a mass of 6,000 x 1020 kg.probes and space missions: US—New Horizons,2006.

Oort cloud(an immense, roughly spherical cloud of icy, cometlikebodies inferred to orbit the Sun at distancesroughly 1,000 times that of the orbit of Pluto)average distance from the Sun: 3–7 trillion km(1.9–4.3 trillion mi)mass: some trillions of the cloud’s icy objects have anestimated total mass of at least 600,000 x 1020 kg(10 times the mass of Earth).