Appendix 2: Solar System Extrema

Here are listed the largest, brightest and densest of the major bodies in the solar system and those with best prospects for life.


 

The Largest

There are 17 bodies in the solar system whose radius is greater than 1000 km.

The composite above shows the Sun and the 5 largest planets at a scale of 3200 km/pixel. (Earth is the tiny spot between Jupiter and the Sun).

This composite shows Earth and the remaining 11 large solar system objects at a scale of 100 km/pixel.

DistanceRadiusMass
NameOrbits(000 km)(km)(kg)
--------------------------------------
Sun6970001.99e30
JupiterSun778000714921.90e27
SaturnSun1429000602685.69e26
UranusSun2870990255598.69e25*
NeptuneSun4504300247641.02e26*
EarthSun14960063785.98e24
VenusSun10820060524.87e24
MarsSun22794033986.42e23
GanymedeJupiter107026311.48e23+
TitanSaturn122225751.35e23+
MercurySun5791024393.30e23+
CallistoJupiter188324001.08e23
IoJupiter42218158.93e22
MoonEarth38417387.35e22
EuropaJupiter67115694.80e22
TritonNeptune35513532.14e22
PlutoSun591352011601.32e22

*Note: Neptune is slightly denser than Uranus.

+Note: Mercury is much denser than Ganymede and Titan.


The Brightest

There are 12 major bodies brighter than magnitude 6 (as viewed from Earth). All of these can be seen with the unaided eye or with binoculars.

DistanceRadius
NameOrbits(000 km)(km)Vo *
----------------------------------
Sun?0697000-26.8
MoonEarth3841738-12.7
VenusSun1082006052-4.4
JupiterSun77800071492-2.7
MarsSun2279403398-2
MercurySun579102439-1.9
SaturnSun1429000602680.7
GanymedeJupiter107026314.6
IoJupiter42218155
EuropaJupiter67115695.3
UranusSun2870990255595.5
CallistoJupiter188324005.6

*Note: Vo = Object’s magnitude in visible light at opposition.

Note: Comets are often quite bright during their brief passage near the Sun.

Warning: Do NOT look directly at the Sun. Looking directly at the Sun can cause severe eye damage; doing so with binoculars or a telescope without specialized solar filters will cause instantaneous and permanent blindness.


The Densest

There are 11 major bodies whose density is greater than 3 g/cm3:

RadiusMass
Name(km)(kg)Dens *
---------------------------
Earth63785.97E+245.52
Mercury24393.30E+235.42
Venus60524.87E+245.26
Adrastea101.91E+164.5
Mars33986.42E+233.94
Io18158.93E+223.53
Moon17387.35E+223.34
Elara387.77E+173.3
Sinope187.77E+163.1
Lysithea187.77E+163.1
Europa15694.80E+223.01

*Note: Density is in grams per cubic centimeter.

Note: Data for the smaller satellites are not very accurate.

There are also many dense asteroids, especially the M-types.


The Best Prospects for Life

NameWhy
----------------
Earth🙂
Marsmost Earth-like; more so in the past
Europamay have liquid water
Titancomplex chemistry and liquids likely
Enceladusmay have liquid water
Iocomplex chemistry, warmer than most
Jupiterlong shot: warm, plenty of organic material

Recent evidence of water on Mars notwithstanding, all of this remains very speculative. None of these prospects are really very good. Good arguments can be made why life (at least life as we know it) cannot exist on any of these bodies. (More about life on Europa.) But even if no life exists on other bodies in our solar system, it seem to be likely that there’s probably life elsewhere in our galaxy. There are good arguments on both sides of that issue, however, the only things most scientists agree upon are that we just don’t know and that more evidence is needed.