View Full Version : neutron stars

2004-Aug-17, 08:36 PM
Found this page today. It's got some pretty good information on Neutron stars (I think).

Got a couple of questions though. I have to admit that I didn't understand quite what all of it was saying.

Anyway, imagine starting at the surface of a neutron star and burrowing your way down. The surface gravity is about 10^11 times Earth's, and the magnetic field is about 10^12 Gauss, which is enough to completely mess up atomic structure: for example, the ground state binding energy of hydrogen rises to 160 eV in a 10^12 Gauss field, versus 13.6 eV in no field. In the atmosphere and upper crust, you have lots of nuclei, so it isn't primarily neutrons yet. At the top of the crust, the nuclei are mostly iron 56 and lighter elements, but deeper down the pressure is high enough that the equilibrium atomic weights rise, so you might find Z=40, A=120 elements eventually. At densities of 10^6 g/cm^3 the electrons become degenerate, meaning that electrical and thermal conductivities are huge because the electrons can travel great distances before interacting.

What is the ground state binding energy and what is the significance of it increasing in a powerful magnetic field? Also what the heck does it mean by finding Z=40, A=120 elements???


When the density exceeds the nuclear density 2.8x10^14 g/cm^3 by a factor of 2 or 3, really exotic stuff might be able to form, like pion condensates, lambda hyperons, delta isobars, and quark-gluon plasmas.

Whate the heck are those things it's talking about forming?

2004-Aug-17, 08:48 PM
hyperons (http://www.capp.iit.edu/~capp/hep/hyperon.html).

"Quark-gluon condensates" sounds as if the particle structure itself is breaking down since quarks make up protons and neutrons and are mediated by gluons. (I think there's a lot of speculation going on here, frankly.)

Eta C
2004-Aug-17, 09:04 PM
When referring to elements, nuclear physicists ususally refer to the number of protons by Z and the total number of nucleons (neutrons and protons) by A. Thus a Z=40 A=120 nucleus is a very heavy isotope of zirconium (usually A=90).

In partiicle physics hyperons are heavier versions of nucleons in which the down and up quarks are replaced by strange quarks. The lambda is a spin 0 hyperon that consists of a down, up, and strange quark.

Quark-gluon plasmas (http://www.bnl.gov/RHIC/QGP.htm) are created at very high energies. They are thought to be a state that existed in the early universe. Experiments at the Relativistic Heavy Ion Collider (http://www.bnl.gov/RHIC/) at Brookhaven National Lab are looking at these by colliding high energy gold nuclei. Check the site out. Some neat pictures

2004-Aug-17, 09:53 PM
You're right, cool pictures, though I like some of the bubble chamber ones better personally.


-Creation of a black hole that would "eat" ordinary matter.

- Initiation of a transition to a new, more stable universe.

- Formation of a "strangelet" that would convert ordinary matter to a new form.

I know that those were looked at and more or less discredited. I even get the idea behind the first, that they would become so dense from the collision that they would form a sort of micro black hole. But the others I don't really follow the idea behind them.