# Chandrasekhar limit & Tolman–Oppenheimer–Volkoff limit

1. Sep 17, 2011

A non-rotating body of electron-degenerate matter above a certain limiting mass must have an infinite density. Now my question is : Why is it resulted as 1.4 times the solar mass in Chandrasekhar limit whereas things finally settled at 3 times the solar mass owing to the Tolman–Oppenheimer–Volkoff limit?? Could anyone please tell me what had brought the change in result of the later one??

and one more thing ... Which is considered as the correct one?? Thank you :)

2. Sep 17, 2011

### mathman

Where did you get that idea?

3. Sep 17, 2011

### Ken G

The lower limit is for degenerate electrons, the latter is for degenerate neutrons. Your question is actually a good one, because both electrons and neutrons need to go relativistic before these limits are reached, and at first glance you might think that electrons and neutrons would behave more or less the same once they are relativistic. But neutrons have access to other types of physics than electrons do, so that's one reason their "equation of state" is different from electrons, even when both are relativistic (in fact, the neutron equation of state is not well known).

4. Sep 18, 2011

http://en.wikipedia.org/wiki/Black_hole ... Thats when I was going through the Wiki of Black Hole. If you really want to know, you can go to the "General Relativity" section in that page.

5. Sep 18, 2011

Thanks for the explanation sir :) So you say that both of them are correct and the 1st limit is for electrons whereas the 2nd one is for neutrons. KindlyLet me know if I got it anywhere wrong !!

6. Sep 18, 2011

### mathman

Since quantum theory is not taken into account, there is a problem in determining what actually happens. Attempts to reconcile G.R. with quantum theory end up with nonsense.

7. Sep 19, 2011

Heard that there is a chance of micro black holes forming in the LHC working @ CERN but got to know that they don't usually and even if they form, they get evaporated within nano seconds. But I have no idea why there is a chance of micro black holes forming in the LHC. Could anyone please tell me why.

8. Sep 20, 2011

### Chronos

Mini black holes will not be produced by the LHC. The energy level is far too low. Were this untrue, we would be bombarded by mini black holes created by high energy cosmic ray collisions with the upper atmosphere.

9. Sep 20, 2011

Yeah...but could you please tell me whats the minimum energy level for mini black holes to form???

10. Sep 20, 2011

### Chronos

In three dimensional space, the minimum energy necessary to form a microscopic black hole is about 10e+19 GeV. This would require a modern circular accelerator about 1000 light years in diameter. The low energy limit estimates [~ 1 TEV] for forming mini black holes assume higher dimensional space where gravity in the 'extra' dimensions can be much stronger. The LHC has found no evidence to date suggesting the existence of 'extra' dimensions.

11. Sep 22, 2011

Thanks Chronos...everything has become clear to me except that "extra dimensions" . Could you please explain this extra dimensions thingy?? :tongue2:

12. Sep 26, 2011

### twofish-quant

Bad explanation. But thanks to the wonders of wiki-dom, I've changed it.

Also the Chandrasekar calculations doesn't use general relativity. Special relativity is enough.