Astronomical Data

  mercury venus earth mars
traditional
symbol
mass
(1024 kg)
0.3302 4.8685 5.9736 0.64185
mean radius
(km)
2439.7 6051.8 6371.0 3390
equatorial radius (km) 2439.7 6051.8 6378.1 3397
polar radius
(km)
2439.7 6051.8 6356.8 3375
flattening
factor
0.0000 0.0000 0.00335 0.00648
moment of inertia constant 0.33 0.33 0.3308 0.366
obliquity of
axis (°)
0.01 177.36 23.45 25.19
semimajor axis
(106 km)
57.91 108.21 149.60 227.92
perihelion
(106 km)
46.00 107.48 147.09 206.62
aphelion
(106 km)
69.82 108.94 152.10 249.23
orbital
eccentricity
0.2056 0.0067 0.0167 0.0935
orbital
inclination (°)
7.00 3.39 0
(by definition)
1.850
siderereal
orbit (days)
87.969 224.701 365.256 686.980
tropical
orbit (days)
87.968 224.695 365.242 686.973
sideral period
(hours)
1407.6 −5832.5 23.9345 24.6229
length of day
(hours)
4222.6 2802.0 24.0000 24.6597
mean surface
pressure (kPa)
10−12 9,200 101.325
(by convention)
0.638
mean surface
temperature (K)
440 737 288 210
blackbody
temperature (K)
442.5 231.7 254.3 210.1
natural
satellites
none none 1 2
planetary
ring system
none none none none
The Inner Planets (Terrestrial Planets)
  jupiter saturn uranus neptune
traditional
symbol
♅, ⛢
mass
(1024 kg)
1,898.6 568.46 86.832 102.43
mean radius
(km)
69,911 58,232 25,362 24,624
equatorial
radius (km)
71,492 60,268 25,559 24,764
polar radius
(km)
66,854 54,364 24,973 24,341
flattening
factor
0.06487 0.09796 0.02293 0.01708
moment of inertia constant 0.254 0.210 0.225 ?
obliquity of
axis (°)
3.13 26.73 97.77 28.32
semimajor axis
(106 km)
778.57 1,433.53 2,872.46 4,495.06
perihelion
(106 km)
740.52 1,352.55 2,741.30 4,444.45
aphelion
(106 km)
816.62 1,514.50 3,003.62 4,545.67
orbital
eccentricity
0.0489 0.0565 0.0457 0.0113
orbital
inclination (°)
1.304 2.485 0.772 1.769
siderereal
orbit (days)
4,332.589 10,759.22 30,685.4 60,189
tropical
orbit (days)
4,330.595 10,746.94 30,588.740 59,799.9
sideral period
(hours)
9.9250 10.656 −17.24 16.11
length of day
(hours)
9.9259 10.656 17.24 16.11
mean surface
pressure (kPa)
n/a n/a n/a n/a
mean surface
temperature (K)
165 134 76 72
blackbody
temperature (K)
110.0 81.1 58.2 46.6
natural
satellites
63 47 27 13
planetary
ring system
1 extensive 13 9
discovery antiquity antiquity William Herschel
13 March 1781
Johann Galle
23 September 1846
The outer planets (The Jovian planets)
  ceres comet halley pluto eris
traditional
symbol(s)
     
family main belt asteroid short period comet kuiper belt object trans-neptunian object
mass
(1024 kg)
0.00095 0.0075 0.0125 ?
mean radius
(km)
975 × 909 16 × 8 1195 1350
obliquity of
axis (°)
? ? 122.53 ?
semimajor axis
(106 km)
413.715 2684 5906.38 10,160
perihelion
(106 km)
380.612 5235 4436.82 5710
aphelion
(106 km)
446.818 89.8 7375.93 14,602.3
orbital
eccentricity
0.080 0.967 0.2488 0.4378
orbital
inclination (°)
10.587 18 17.16 43.993
siderereal
orbit (days)
1679.819 −28,361–603 90,465 203,500
tropical
orbit (days)
? ? 90,588 ?
sideral period
(hours)
9.0744 ? −153.2928 ?
length of day
(hours)
? ? 153.2820 ?
mean surface
pressure (kPa)
? ? 0.0003 ?
mean surface
temperature (K)
167 ? 50 ?
blackbody
temperature (K)
? ? 37.5 ?
natural
satellites
0 0 4 1
discovery Giuseppe Piazzi
1 January 1801
antiquity Clyde Tombaugh
18 February 1930
Brown, Trujillo, Rabinowitz 5 January 2005
Selected minor bodies
  io europa ganymede callisto
mass
(1022 kg)
8.932 4.800 14.819 10.759
mean radius
(km)
1821.6 1560.8 2631.2 2410.3
semimajor
axis (km)
421,600 670,900 1,070,400 1,882,700
orbital
eccentricity
0.004 0.0101 0.0015 0.007
orbital
inclination (°)
0.04 0.47 0.21 0.51
siderereal
orbit (days)
1.769138 3.551181 7.154553 16.689018
discovery Galileo Galilei
7 January 1610
The Galilean satellites of Jupiter
  moon titan triton charon
traditional
symbol(s)
☾ ☽      
satellite
of …
earth saturn neptune pluto
mass
(1022 kg)
7.349 13.45 2.14 0.162
mean radius
(km)
1737.1 2575 1353.4 593
semimajor
axis (km)
384,400 1,221,850 354,760 19,600
perigee
(km)
363,300
apogee
(km)
405,500
orbital
eccentricity
0.0549 0.0292 0.000016 0.0002
orbital
inclination (°)
5.145 0.33 157.345 0.0
siderereal
orbit (days)
27.3217 15.945421 −5.876854 6.38725
mean surface
pressure (kPa)
10−13 150 ? ?
mean surface
temperature (K)
100–400 95 ? ?
discovery antiquity Christiaan Huygens
25 March 1655
William Lassell
10 October 1846
James Christy
22 June 1978
Selected large satellites
  sun proxima centauri sirius betelgeuse
traditional
symbol
     
mass 1.989 × 1030 kg  
 
0.12 m  
 
2.14 m 12-17 m
radius 6.960 × 108 m  
 
0.12 r  
 
1.68 r 650 r
luminosity 3.839 × 1026 W  
 
0.0009 L  
 
26.1 L 9400 L
temperature 5780 K  
 
2670 K  
 
9900 K 3100 K
type G2
(main sequence)
M5
(red dwarf)
A1
(main sequence)
M1
(red supergiant)
distance
from earth
1.496× 1011 m 4.27 light years 8.57 light years 520 light years
Selected Stars