Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Stephanie on 06/09/2009 11:30:03

Title: What keeps planets from being crushed by gravity like stars?
Post by: Stephanie on 06/09/2009 11:30:03
Stephanie asked the Naked Scientists:
   
As I understand it the nuclear fusion of stars stops gravity from compressing them until they cannot be compressed anymore because of the force of the neutrons repelling each other; when stars run out of fusible materials they are compressed to this point.

So what keeps the planets from being compressed by gravity as the stars are when they run out of fusible materials?

What do you think?
Title: What keeps planets from being crushed by gravity like stars?
Post by: lightarrow on 06/09/2009 11:36:24
Quote from: Stephanie on 06/09/2009 11:30:03
Stephanie asked the Naked Scientists:
   
As I understand it the nuclear fusion of stars stops gravity from compressing them until they cannot be compressed anymore because of the force of the neutrons repelling each other; when stars run out of fusible materials they are compressed to this point.

So what keeps the planets from being compressed by gravity as the stars are when they run out of fusible materials?

What do you think?
A planet's mass is much lower than a star's mass.
Title: What keeps planets from being crushed by gravity like stars?
Post by: lyner on 06/09/2009 12:51:45
. . . . .  so the internal gravitational attraction is not enough to cause crushing. The atoms are strong enough to withstand the force in planets.

(added for clarity, lightarrow - OK?)
Title: What keeps planets from being crushed by gravity like stars?
Post by: lightarrow on 06/09/2009 18:27:28
Quote from: sophiecentaur on 06/09/2009 12:51:45
. . . . .  so the internal gravitational attraction is not enough to cause crushing. The atoms are strong enough to withstand the force in planets.

(added for clarity, lightarrow - OK?)
Ok. I was lazy, didn't want to add anything else  [:)]
Title: What keeps planets from being crushed by gravity like stars?
Post by: wanhafizi on 07/09/2009 16:15:36
Quote
So what keeps the planets from being compressed by gravity as the stars are when they run out of fusible materials?

But, for some stars, humangeous super nova explosion compress the centre of the star...

...i think...
Title: What keeps planets from being crushed by gravity like stars?
Post by: LeeE on 07/09/2009 22:28:54
The radiation implosion of a super-nova that results in a black hole isn't really too different from the radiation implosion that is used to start the fusion process in fission-fusion and fission-fusion-fission bombs.

I believe that much of the initial mass of a pre-super-nova star is blown away by the explosion and the mass of the resulting neutron star or BH is far less than the star's original mass i.e. although our sun could form a BH if it were 1.4 times larger, the resulting BH would have less than 1.4 solar masses.

Not sure about this though, off hand.
Title: What keeps planets from being crushed by gravity like stars?
Post by: thedoc on 08/09/2009 18:37:02
Listen to the answer to this question on our podcast. (http://www.thenakedscientists.com/HTML/podcasts/show/2009.09.05/)