World Buildersâ„˘                                                                         Session One -- Astronomy     Star Tables                                       Simplified,                                               Star Types that might support  Life-Bearing Planets Think carefully and choose your star type from the tables below.

These star tables and some of the comments were sent to us by Gerald Nordley, science fiction writer, member of the CONTACT group, and a very good friend to world builders! Thank you very much for your help, Mr Nordley!

This is a very basic star table.

Notes on these star tables:

The stars in these tables are arranged in the classes used in the Main Sequence. Choose your star from these tables and you will have some of the numbers that you need for your solar system and your planet.

Our sun is a G2 star. As we found out from our hands-on activity, our sun formed 4.5 billion years ago. Earth also formed about 4.5 billion years ago, and 3.8 billion years ago, or perhaps even earlier, the first single celled life forms appeared. When you consider that the earth had to cool from a molten state first, life seems to have appeared quite quickly. However, the jump to multicellular life forms took a long time. Multicellular life forms began to develop only 600 million years. If you want to have life forms that you can actually see, you need to choose a star with a long enough life time.

You should choose your star type from these tables. Choose the ones with yellow in their rows:  the others are for your reference/  Write down the information about your star's row, with the headings.

Class: See the page on Main Sequence

Temperature in Degrees Kelvin:  See page on Temperatures in Space. The temperature given is the surface temperature of the star.

Mass (Mass of our sun = 1): See page on Weight, Mass, and Density.

Radius:  The radius is the distance from the center of the star to its surface.

Terrestrial Equivalent Orbit in AUs:

the distance to a star where the planet gets Earth's solar intensity (1372 W/m^2). For very dim stars, planets would have to be very close, and tidal effects are of concern.

This is how long your star will burn in a stable way. Remember, you need to allow time for your life forms to develop.

If you look at these tables you will see interesting changes as the stars get smaller. Pay special attention to the colored sections of the tables: you will be using these numbers in planning your own solar system.  Choose your star from the rows that have yellow with them.

Stars of types O, B, and A do not have long enough life spans to allow complex life to develop.

Stars of types A, F, and G could possibly have life bearing planets.

Stars of our types M and E0 are so cool that planets orbiting them could be tidally locked (the same face is always turned toward the sun).  They might also get zapped by solar flares.

 Class Characteristics Temperature in Degrees Kelvin Mass (Mass of our sun =1) Radius (Radius of Sun=1) Terrestrial Equivalent Orbit in AUs Lifetime  in billions of earth years O O4- O9 Very Large, Very Hot, Very Fast Burning 48000 - 33000 90.000 - 23.300 14.400 - 9.560 995.00 = 311.00 .002 - .009 B B0-B9 Hot and Fast Burning 33000 - 10500 17.500 - 3.350 8.470 - 2.960 228.00 - 9.75 .010 - .475 A A0-A8 Do Not Last Long Enough to Support Complex Life Forms 9520 - 7580 2.900 - 1.600 2.710 - 1.710 7.35 - 2.93 .583 - 1.290 F  F0-F8 Some of These Might Have Life-Bearing Planets 7200 - 6200 1.600 - 1.190 1.640 - 1.260 2.55 - 1.45 1.600 - 6.880 G G0-G8 Possible Suns for Planets with Life: The Sun is a G2 Star 6030 - 5570 1.050 - .642 1.130 - .875 1.22 - .81 9.180 - 17.900 K K0-K7 Small, Dim, Red Stars: Could Perhaps Support Life On Inner Planets 5250 - 4060 .790 - .606 .786 - 641 .65 - .32 21.00 - very long M M0-M9 Less than Half the Mass of Our Sun 3850 - 2510 .510 -.100 .626 -.092 .28 - .017 Very, very long E E0-E8 Brown Dwarfs Heat-Radiating Bodies Less Than a Tenth the Mass of Our Sun E0 is a lowest mass star. The others are Brown Dwarfs 1800 - 800 .080 - .040 .065 - .177 .0063 - .0022 Even longer J J0-J9 not stars Astronomical Bodies Smaller than Mass of Jupiter: Radiate Heat 700 - 50 Too dim for us to see smaller than Jupiter .118 - .037 .0017 - below surface of planet Possibly longer than the life of the Universe!

The three star classes below contain stars that could be orbited by life-bearing planets.
 Class F Stars: Some of These Might Have Life-Bearing Planets Class Temperature in degrees Kelvin Mass (Mass of our sun = 1) Radius (Radius of Sun=1) Terrestrial Equivalent Orbit in AUs Lifetime in billions of years F0 7200 1.600 1.640 2.55 1.600 F2 6890 1.520 1.460 2.07 1.760 F5 6440 1.400 1.440 1.79 3.440 F8 6200 1.190 1.260 1.45 6.880

 G Class Stars: Possible Suns for Planets with Life: The Sun is a G2 Star Class Temperature in degrees Kelvin Mass (Mass of our sun = 1) Radius (Radius of Sun=1) Terrestrial Equivalent Orbit in AUs Lifetime in billions of years G0 6030 1.050 1.130 1.22 9.180 G2 5860 .998 1.020 1.05 10.100 G5 5770 .920 .893 .89 14.000 G8 5570 .842 .875 .81 17.900

 K Class Stars: Small, Dim, Red Stars: Could Perhaps Support Life On Inner Planets Class Temperature in degrees Kelvin Mass (Mass of our sun = 1) Radius (Radius of Sun=1) Terrestrial Equivalent Orbit in AUs Lifetime in billions of years K0 5250 .790 .786 .65 21.100 K1 5080 .766 .788 .61 long K2 4900 .742 .750 .54 K3 4730 .718 .762 .51 K4 4590 .694 .692 .43 very K5 4350 .670 .684 .39 long K7 4060 .606 .641 .32