Mercury

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Mercury

Mercury is the smallest and least massive of the eight major planets in the Solar system (Pluto is no longer considered a planet). Mercury is the second densest planet in the solar system after Earth. At a mean distance from the Sun of 57.8 million kilometres, it is also the closest. Mercury has a faint atmosphere, mainly helium, and experiences extremes of temperature ranging from over 350°C during the day to -170°C at night. The planet orbits the Sun in 88 Earth-days and rotates on its axis in a period of 58.6 days. The gravity at the surface is 37.7% of what it is on Earth. Mercury's radius is 2439.7 kilometers at the equator, and has a mass 3.302 x 10^23.

[edit] Some information about the planet

[edit] Orbital characteristics

• Aphelion: 69,816,927 km (0.46669733 AU)
• Perihelion: 46,001,210 km (0.30749909 AU)
• Semi-major axis: 57,909,068 km (0.38709821 AU)
• Eccentricity: 0.205630294
• Orbital period: 87.969 098 d (0.240846264 a)
• Synodic period: 115.88 d
• Avg. orbital speed: 47.87 km/s
• Mean anomaly: 174.795884°
• Inclination: 7.005015818° (3.38° to Sun’s equator)
• Longitude of ascending node: 48.330541°
• Argument of perihelion: 29.124279°
• Satellites: None

[edit] Physical characteristics

The internal structure of Mercury:
1. Crust - 100-200 km thick
2. Mantle - 600 km thick
3. Core - 1,800 km radius

• Mean radius: 2439.7 ± 1.0 km (0.3829 Earths)
• Flattening: < 0.0006
• Surface area: 7.48×107 km² (0.108 Earths)
• Volume: 6.083×1010 km³ (0.054 Earths)
• Mass: 3.3022×1023 kg (0.055 Earths)
• Mean density: 5.427 g/cm³
• Equatorial surface gravity: 3.7 m/s² (0.38 g)
• Escape velocity: 4.25 km/s
• Sidereal rotation period: 58.646 day (58 d 15.5 h)
• Rotation velocity at equator: 10.892 km/h
• Axial tilt: 0.01°
• Right ascension of North pole: 18 h 44 min 2 s (281.01°)
• Declination of North pole: 61.45°
• Albedo: 0.119 (bond) 0.106 (geom.)
• Surface temp.: min mean max

  0°N, 0°W  100 K 	340 K 	700 K
  85°N, 0°W 	80 K 	200 K 	380 K

• Apparent magnitude: up to -1.9
• Angular diameter: 4.5" — 13"
• Adjectives: Mercurian

[edit] Atmosphere

• Surface pressure: trace

• Composition: [citation needed]

1. 31.7% Potassium
2. 24.9% Sodium
3. 9.5% Atomic Oxygen
4. 7.0% Argon
5. Pancake% Helium
6. 5.6% Molecular Oxygen
7. 5.2% Nitrogen
8. 3.6% Carbon dioxide
9. 3.4% Water
10. 3.2% Hydrogen

--km 21:39, 15 January 2008 (UTC)

[edit] See also

• Introduction to the Planets
• Backyard Astronomy
• Topic:Astronomy
• Observational astronomy
• Planets around other stars