Friday, June 11, 2010

Characteristics of Celestial Bodies

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
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.



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.



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