World Builders™                                                                        Session One  --  Astronomy
                                        
Information about

Planets and Moons In our Solar System

This information will help you to pick sizes and densities for your world.

     Here is some information about the planets and moons in our own solar system. I have gathered these numbers from many sites on the web, the majority of them being NASA sites.

     Look at these tables to get some ideas of planet and moon sizes. Then you can decide what you want your planet to be like.

Hints:

Work out your year length first.  

Check Kepler's Third Law to see how to do the math.

Check out Circle Talk to help you with getting your planets to the right size.  
Use the
Earth = 1 measurements.

     You can pick just about any day length that you like. To be on the safe side, make it more than about 8 hours. If the day length is too short, the planet might come apart.  This would happen if the speed of the planet at the equator is faster than the escape velocity from that world.

     Go to Calculating Your Planet's Gravity when you have decided on either the radius (blue) or the Density in grams/cm^3  (in 0range column) of your planet. You can also Calculate Your Moon's Orbit.

Our Solar System -- Planets and the Sun

  Year Length in Earth Years Day Length
in
Earth Days
Distance from Sun in AUs  Radius in Kilo- meters  Radius When Radius of Earth = 1  Mass When Mass of Earth =1 Density
when Density of Earth
=1 
 Den-
sity
in
grams
 cm^3
Gravity
 when Gravity of Earth = 1
Escape Velocity in Kilo- meters/
Second
Mean
Kelvin Temp-
erature   
(Minimum- Maximum)
Atmos-
phere 
Moons
 Sun   .  0 700,000 109 332800  .25 1.41      6000  -  -
Mercury     .2
(88 days)
176 days  .39  2,440 .38  .05  .98 5.43  .4  4.3  452
(100 - 700)
   0
Venus      .6
(225 days)
117 days
one revol-
ution 243 days
 .72  6,052 .95  .89  .95 5.25  .9  10.4  726 Carbon Dioxide 96%
Density
 is 100 times 
Earth
 0
 Earth   1 24. hrs  1  6,378 1  1  1 5.52  1  11.2  281
(260 - 310)
Nitrogen 77%
Oxygen 21%
Other 2%
 1
 Mars  1.9 24.6 hrs  1.5  3,397 .53  .11  .71 3.95  .4  5.0  (150 - 310) Thin Carbon Dioxide atmos_
phere
 2
 Jupiter  12 10 hrs  5.2  71,492 11  318  .24 1.33  2.5  59.5 120 at cloud
 tops
   16 or 
more
 Saturn  29.5 10 hrs  9.5  60,268 9.5  95  .125 .69  1  35.6  88    19 or 
more
 Uranus  84 16.5 hrs 19.2  25,559 4  15  .23 1.29  .9  21.30  59    
 Neptune  165 16 hrs 30.1  24,766 4  17  .3 1.64  1.1  23.3  48    8 or 
more
 Pluto  248.6 6.4 hrs 39.5   1,137 .18  .002  .37 2.03  .5 ?  1.1  37    1

Here is some information on Moons. You can see that they come in many sizes, so you have a lot of choice. Be sure to locate your moons outside The Roche Limit!

 Information about Some Moons in 0ur Solar System

Orbits around Period for One Orbit Around the Planet in Earth
Days

 Diameter

in km

Radius When Radius of Earth = 1 Mass when Mass of Moon = 1 Mass in Kg Density
 in grams
cm^3
Escape Velocity in Kilometers/
Second

Average Distance from its Planet in Km

 moon  earth  27.3  3476  .27  1  7.35*10^25  3.34  2.4  384,400
 Deimos  Mars  1.23  12.6  .001    1.8 *10^15  1.7    23,460
 Phobos  Mars  .3  22.2 .002    1.08*10^16  2.0    9,380
Callisto  Jupiter  16.7  4800  .38  1.5    1.8    1,883,000
 Ganymede  Jupiter  7.1  5262  .4  2   1.93    1,070,000
 Europa  Jupiter  3.5  3138  .25  .7    3.04   670,900 
 Io  Jupiter  1.8  3630  .28  1.2    3.55    422,000
 Titan  Saturn  15.9  5150  .4  1.9    1.88  1,221,830
 Dione  Saturn  2.7  1120  .15    1.05*10^24  1.4    377,400
 Tethys  Saturn  1.9  1060  .08    6.26*10^23  1    295,000
 Rhea  Saturn  4.5  1530  .12    2.28*10^24  1.3    527,040
 Mimas  Saturn  .9  392  .03    3.7*10^22  1.2    185,520
 Iapetus  Saturn  79  1460  .11    1.93*10^24  1.1    3,561,300

Astronomy Information Menu

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© 1998, 2003. Elizabeth Anne Viau. All rights reserved. This material may be used by individuals for instructional purposes but not sold. Please inform the author if you use it at eviau@earthlink.net.