Info

mercury

Mercury
Designations
Pronunciation /ˈmɜːrkjəri/
Adjectives Mercurian,[1] mercurial[2]
Orbital characteristics[5]
Epoch J2000
Aphelion
  • 0.466 697 AU
  • 69,816,900 km
Perihelion
  • 0.307 499 AU
  • 46,001,200 km
Semi-major axis
  • 0.387 098 AU
  • 57,909,050 km
Eccentricity 0.205 630[3]
Orbital period
  • 87.969 1 d
  • 0.240 846 yr
  • 0.5 Mercury solar day
Synodic period
115.88 d[3]
Average orbital speed
47.362 km/s[3]
Mean anomaly
174.796°
Inclination
  • 7.005° to ecliptic
  • 3.38° to Sun's equator
  • 6.34° to invariable plane[4]
Longitude of ascending node
48.331°
Argument of perihelion
29.124°
Satellites None
Physical characteristics
Mean radius
  • 2,439.7±1.0 km[6][7]
  • 0.3829 Earths
Flattening 0[7]
Surface area
  • 7.48×107 km2[6]
  • 0.147 Earths
Volume
  • 6.083×1010 km3[6]
  • 0.056 Earths
Mass
  • 3.3011×1023 kg[8]
  • 0.055 Earths
Mean density
5.427 g/cm3[6]
Surface gravity
  • 3.7 m/s2
  • 0.38 g[6]
Moment of inertia factor
0.346±0.014[9]
Escape velocity
4.25 km/s[6]
Sidereal rotation period
  • 58.646 d
  • 1407.5 h[6]
Equatorial rotation velocity
10.892 km/h (3.026 m/s)
Axial tilt
2.04′ ± 0.08′ (to orbit)[9]
(0.034°)[3]
North pole right ascension
  • 18h 44m 2s
  • 281.01°[3]
North pole declination
61.45°[3]
Albedo
  • 0.068 (Bond)[10]
  • 0.142 (geom.)[10]
Surface temp.minmeanmax
0°N, 0°W [11] 100 K 340 K 700 K
85°N, 0°W[11] 80 K 200 K 380 K
Apparent magnitude
−2.6[12] to 5.7[3][13]
Angular diameter
4.5–13″[3]
Atmosphere[14]
Surface pressure
trace (≲ 0.5 nPa)
Composition by volume
  • 42% molecular oxygen
  • 29.0% sodium
  • 22.0% hydrogen
  • 6.0% helium
  • 0.5% potassium
  • Trace amounts of argon, nitrogen, carbon dioxide, water vapor, xenon, krypton, and neon