1,122RPS

Innocent Bystander · Post by **Innocent Bystander** » Sun Feb 18, 2007 4:53 am

So, is there a limiting condition?
How fast would it be physically possible for a star to spin?

Coffee · Post by **Coffee** » Sun Feb 18, 2007 7:23 am

Well, a spin exerts a force on the material of an object. This can be observed on our own planet, whose rotation causes the earth to not be a perfect sphere, but rather to 'bulge' out in the middle. This applies to just about any rotating object.

To answer your question though, yes there is an upwards limit on how fast a star can spin. I don't remember the exact equation, but it is related to the star's total mass. Basically, the more massive the star the greater is gravitational pull and therefore the faster it can spin without the rotational force literally ripping it apart. If a star is spinning close to its own escape velocity, it'll be pretty oblate indeed.

Jack · Post by **Jack** » Sun Feb 18, 2007 12:06 pm

the article wrote:A thimbleful would weigh a hundred million tons back here on Earth.

That's difficult for me to understand.

Coffee · Post by **Coffee** » Sun Feb 18, 2007 12:20 pm

Consider that the most dense naturally occuring matter here on earth is mostly empty space (can pass neutrinos(sp) through it) with electron clouds moving at great distances from atomic neucleii (relative to the size of the particles) and it'll be easier to grasp.

TyroneShoelaces · Post by **TyroneShoelaces** » Sun Feb 18, 2007 1:26 pm

Denny wrote:

"artist's impression"

dang...i really thought we were onto something here.

~shoelaces~

Innocent Bystander · Post by **Innocent Bystander** » Tue Feb 20, 2007 7:49 am

Cofaidh wrote:Well, a spin exerts a force on the material of an object. This can be observed on our own planet, whose rotation causes the earth to not be a perfect sphere, but rather to 'bulge' out in the middle. This applies to just about any rotating object.

To answer your question though, yes there is an upwards limit on how fast a star can spin. I don't remember the exact equation, but it is related to the star's total mass. Basically, the more massive the star the greater is gravitational pull and therefore the faster it can spin without the rotational force literally ripping it apart. If a star is spinning close to its own escape velocity, it'll be pretty oblate indeed.

I had a chat about this with a (mathematical) friend.
He said the limiting condition would be the speed of light, and it would be the speed of the star at its equator. But, since mass increases and length decreases as you approach the speed of light, the star would tend to collapse in on itself and become a black hole, if it rotated fast enough. Does that sound right?

Coffee · Post by **Coffee** » Tue Feb 20, 2007 1:34 pm

Sounds about right yeah, though for that to be the case the escape velocity for the pulsar would have to be approaching the speed of light.

Congratulations · Post by **Congratulations** » Tue Feb 20, 2007 1:37 pm

Cranberry wrote:
the article wrote:A thimbleful would weigh a hundred million tons back here on Earth.
That's difficult for me to understand.

I believe (keep in mind, I'm a humanities major) that the implication is this: It's so dense that, should you have a volume of it similar to that of a thimble in Earth's gravity, it would weigh something close to 100,000,000 tons.

Flyingcursor · Post by **Flyingcursor** » Tue Feb 20, 2007 5:59 pm

It looks to me as if someone is having a sip of a refreshing soft-drink.

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