sigidunum@[EMAIL PROTECTED]
wrote:
> I'm told here's some reason to think a white dwarf might have planets
> -- either survivors from its main sequence days (possibly somewhat,
> er, ablated), or new planets that might condense after the transition
> to a white dwarf.
Well, after all, the first extrasolar planets were discovered orbiting
around white dwarfs.
> A white dwarf with a temperature similar to the Sun would be about
> 1/10,000 as bright, so a planet would have to be 100 times closer than
> Earth to be comfortable. Presumably a planet in the habitable zone
> would be tidally locked. (Or would it? IMS tidal forces are affected
> by the radius of the primary; does anyone know the exact
> relation****p?)
To first order it's the mass, which should put it easily enough in the
realm where the planets would have to be tidally locked.
> Still, if we can imagine a habitable tidally locked "ribbon world" in
> a close orbit around a red dwarf, why not around a white dwarf? Is
> there anything that makes the idea ridiculous?
The cooling timescale for white dwarfs is pro****tional to (L/M)^(-5/7),
so for a white dwarf with about ten times the luminosity you're talking
about (10^-3 L_sun), the timescale is ~1 Gyr.
--
Erik Max Francis && max@[EMAIL PROTECTED]
&& http://www.alcyone.com/max/
San Jose, CA, USA && 37 18 N 121 57 W && AIM, Y!M erikmaxfrancis
I woke up this morning / You were the first thing on my mind
-- India Arie
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