Solar Systems
Our prejudice, based on our own experience, is that the evolution of life requires a narrow range of
conditions realized in a system of planets and/or moons around a long-lived star. As we discussed in
Chapter 5, we now have rapidly
growing evidence for planets and protoplanetary disks around other stars. The adjacent right figure
and the table below summarize some of the candidates for extrasolar planets.
The extrasolar
planets found so far around normal stars
do not appear to be Earth-like in either size or distance from their star.
However, the fact that they
exist makes us confident that our Solar System is not an aberration and that the formation of planetary
sytems must be a common thing. If the formation of planetary systems is common, we may expect that
in some cases Earth-like planets form. Given the evidence in our own case that life evolved within
a billion years on this Earth-like planet, this gives us considerable confidence that those conditions
may be replicated in many other places.
|
Some Candidates for Extrasolar Planets
|
| Star |
Spectral Class |
Star Dist (ly) |
Dist (AU) |
Mass |
Period (days) |
Ecc
|
| 51 Peg |
G2 |
45 |
0.05 |
0.5 - 1 MJ |
4.23 |
0.09
|
| PSR 1257+12 |
6.2 ms pulsar |
1630 |
0.19 |
0.015 ME |
25.34 |
0.00
|
| PSR 1257+12 |
6.2 ms pulsar |
1630 |
0.36 |
3.4 ME |
66.54 |
0.0182
|
| PSR 1257+12 |
6.2 ms pulsar |
1630 |
0.47 |
2.8 ME |
98.22 |
0.0264
|
| Rho 1 Cnc |
G8 |
253 |
0.11 |
0.84 MJ |
14.65 |
0.05
|
| Rho CrB |
G0V |
50 |
0.23 |
1.13 MJ |
39.6 |
0.028
|
| Tau Boo |
F7V |
180 |
0.046 |
3.87 |
3.31 |
0.00
|
| Upsilon And |
F8V |
187 |
0.057 |
0.68 MJ |
4.611 |
0.00
|
| 47 Uma |
G0V |
47 |
2.1 |
> 2.39 MJ or <4.8 MJ |
1088 |
0.03
|
| 70 Vir |
G4V |
80 |
0.43 |
6.6 - 9 MJ |
116.6 |
0.40
|
|
|
|
|
Adapted from: G. H. Bell
(http://www.public.asu.edu/~sciref/exoplnt.htm)
|