On 12 veebr, 17:58, Brian Davis <brda...@[EMAIL PROTECTED]
> wrote:
> On Feb 11, 2:23 pm, Crown-Horned Snorkack <chornedsnork...@[EMAIL PROTECTED]
>
> wrote:
>
> > There are plenty of main sequence orange dwarfs in globular clusters.
>
> Fair enough, if you have an old enough population of stars, you can
> have old and coolish white dwarfs (although the metallicities in
> globular might be low enough to make for some interesting planet
> formation mechanics as well). It seems I overestimated the number of
> cooler stars. Is there any hard data on the population density of
> white dwarfs of various temperatures (corrected for observational
> bias, as much as possible?)
>
> > As for nearby "white" dwarfs, Procyon B is just about 7500 K, and it
> > is considerably younger than Sun.
>
> Yep. It should also have a BB UV emission about 100 times that of the
> Sun, if I did my numbers right. Even for a star around 6000 K, you
> expect a UV increase of twice that of the Sun, roughly speaking. The
> question then becomes "how much UV can an early biosphere handle",
> which is a tougher question.
>
> > Simply drop the distance and central mass from the equation, and
> > express the tidal locking limit in terms of orbital period.
>
> > This leaves the variables of 2nd order Love #, Quality factor, initial
> > rotational period and density of the planet.
>
> OK, *if* I got my math right,
>
> P_orbital = ( 0.104 {(k2/Q) / rho}^(1/6) T P_rotational )^(1/4)
>
> I'm not sure that's a lot easier, but I think that's the form you were
> implying (with very odd units: T in years, P_orbital in years, and
> P_rotational in hours, ugh). The original I got out of Burn's
> "Satellites", for comparison.
>
What is the unit of rho, for the matter?
Inside the Solar System, T is practically constant. P_rotational is
unknown and unknowable.
Looking at it this way:
Venus, with 228 days orbit, has free rotation - even though slow free
rotation should be easily stopped by even weak tides.
Mercury, with 88 days orbit, is locked - but locked to 3:2, not 1:1.
Moon, at 27 days, is locked 1:1. So is Iapetus, at 79 days. However,
Hyperion, with just 21 days orbit, rotates freely.
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