Re: Planets around a white dwarf

On Feb 11, 9:39 pm, Brian Davis <brda...@[EMAIL PROTECTED]
> wrote:

> > A white dwarf with a temperature similar to the Sun would be about
> > 1/10,000 as bright
>
> I'm not sure there are a lot of these around. Given the current age of
> the universe (young, compared to white dwarf cooling times), the very
> oldest white dwarfs might be a few thousand K... but you won't find
> any very old white dwarfs to begin with, because early star formation
> was biased towards very large stars (that don't leave white dwarfs).

Actually, the problem is the other way 'round: cool white dwarfs are
hard to detect, because they're dim /and/ their spectra are down in
the main sequence.

The coolest known white dwarf is around 4300K, which is really more
yellow than white -- that's quite a bit cooler than the 5200K Sun.
There are claims of old white dwarfs as cool as 3500K, but they're...
not universally accepted.  But there are, no question, a number of
white dwarfs cooler than the Sun.


Doug M.