Greetings to denizens of this fine TML:
I have been monitoring the discussion on TML these last few weeks about
the distribution of stellar classes. With some free time after my last PDE
class, I decided to do a quick survey of the space around Sol. Please note
that these figures are very round and do not necessarily reflect the universe
as a whole.
There are apx 100 stars within 6.5pc of Sol, with almost half of these
stars members of binary of multiple star systems.
Counting the occurence of each spectral class gave these numbers:
Class #
O 0
B 0
A 2
F 1
G 8 (including Sol)
K 14
M 66
Dwarf 8
TOTAL 99
The class Dwarf lumps anything not in the other classes together.
The ratio of O-B-A stars to the rest of the classes is about
1:38. Bright, large stars are rare.
Already we can see how the small, dim M class stars dominate the
population. If any of these stars have planetary systems, the chance of them
being inhabitable are slim. Also, being small, the most these stars will
probably have are planetoid belts. Larger planets (size 3+) are probable going
to be rare. After all, if there was a lot of material around when the star
formed, the star would probably have been bigger.
From this, it seems that the probability tables in SpaceMaster are
fairly accurate (at least for gaming purposes). I havent checked the tables in
WBH yet (my copy is at home), but over the weekend, I will strive to extend this
population survey to more stars and post results next week.
There has also beed discussion of the different types of spectral
classes and their relationship to each other.
In addition to the O-B-A-F-G-K-M classes, there are other types of
stars, including the misunderstood R-N-S classes. These classes include:
Wolf-Raynet Stars: O-type stars with emmission spectra possibly caused
by the ejection of material from the star at high velocity. Planets around
this O-type star would possibly be severly cooked.
Peculiar A Stars: The name says it all. These are A-type stars with
strong absorption lines of certian ionized metals.
R Stars: R-type stars are similar to K-type stars, except for molecular
bands of C2 and CN are present.
N Stars: N-type stars are similar to M stars, except for bands of
C2, CN, CH. R and N stars are also called carbon stars.
S Stars: S-type stars are like M stars, except for bands of zirconium
oxide and lanthanum oxide present with, or addition to, titanium oxide.
These lesser type stars are extremely rare (estimates of <1000
Wolf-Raynet stars in our Galaxy).
As for the distribution of stars through space, Near-Sol surveys give a
population of aboput 59 stars within 5pc of Sol. Extending this out (and the
extension seems to work pretty well) gives an average of one star for every 9
cubic parsecs.
More data to follow later.
Vanya