Re: FT Taskforce and Fleet Actions

On Tue, 7 August, 2001 1:42 PM	Mark 'Indy' Kochte wrote

> On Tue, 7 Aug 2001, Ryan M Gill wrote:
>
> > Course getting the Sun to become a black hole when it isn't over the
> > Chandrakar (sp?)
> > limit is of course impossible. Thats the nice thing about a main
> > sequence dwarf.
>
> Chandrasekhar Limit, which is 1.4 M(solar). My info is a little out of
> date (it's been a LONG time since I seriously studied black holes, and
> really most recently only galactic-sized super-massive BHs), but I
think
> there was theoretical evidence that you could have a black hole of 1
solar
> Mass.

The Chandrasekhar limit is the mass above which electron degeneracy
pressure
will not balance gravitational forces in a white dwarf (leading to
collapse
into a neutron star, in which neutron degeneracy pressure is the
"counter-agent" to gravity).

Beyond about 2 Msolar, neutron deg. pres. is not enough to balance
gravitational forces and you'll have a black hole.

So if a big main sequence star (say, 20 Msolar) goes "kablooey"
(technical
term) when it exhausts its nuclear fuel, and the central remnant is over
2
solar masses, you'll get a black hole.

http://archive.ncsa.uiuc.edu/Cyberia/NumRel/BlackHoles.html
Lots of info about black holes, spacetime wrinkles & stuff like that.

> In any event, what Jerry was trying to illustrate is simply that the
mass
> should be irrelevant when looking at the overall gravity well effects.
You
> could look at all masses as point-sources for this exercise, too.

Yup.  Except when it comes to getting really close to very dense
objects.

> > Ok, I see, the slope is sooner for the gravity well in the case of
> > the larger star. But is the well as deep since it's spread out?
>
> Be careful your adjective "larger". Do you mean more volume or more
mass?
> It does play a difference. ;-)
>
> IIRC (without having all my texts onhand and no time to spend going up
to
> the library to do this research) the volume of the source plays a role
in
> how wide the gravity well is, but the depth should be essentially the
> same for the same mass.

What matters really is _density_.  Lots of stuff in a small volume.

> Don't hurt your head on this stuff. Find a good PSB solution.  :-)

Amen!

Cheers,

Jerry Acord
acord@imagiware.com