Neutron Stars Partially Dissected

mmol_6453 writes "An article at ScienceDaily details and explains observations that offer the first proof that what we consider neutron stars really are neutron superfluids. The original press release can be found here."

Comments

forgot plasma

[wotevah]

As we all know, there are actually four states of matter: solid, liquid, gaseous and plasma.

Re:Cool stuff

[Spock the Baptist]

Thought that I'd throw out a few links on the subject of quark stars. Here's a few useful, and informative links:

http://www.aip.org/enews/physnews/2002/split/585 -1 .html
http://itss.raytheon.com/cafe/qadir/q1401.h tml
http://slashdot.org/science/02/04/10/1840222. shtml ?tid=160
http://news.bbc.co.uk/1/hi/sci/tech/1922 574.stm
http://www.fi.uib.no/~nyiri/thesis.html

Re:Cool stuff

[Iainuki]

Quote from Carroll and Ostlie (a standard undergraduate astrophysics text): "A very general argument involving the general theory of relativity shows that the maximum mass possible for a neutron star cannot exceed about 3 Msun. If a neutron star is to remain dynamically stable and resist collapsing, it must be able to respond to a small disturbance in its structure by rpaidly adjusting its pressure to compensate. However, there is a limit to how quickly such an adjustment can be made becasuet hese changes are conveyed by sound waves that must move more slowly than light. If a neutron star's mass exceeds 3 Msun, it cannot generate pressure quickly enough to avoid collapsing." Neutron stars can't have have masses of 10 suns.

Please back up your assertions!

[Scott Carnahan]

yet within this small region may be over 10 solar masses of material.

Had you read the article, you would have seen that neutron stars are thought to contain the mass of about 1.4 suns. Barring certain speculative theories of exotic matter, no cold (i.e., not undergoing fusion) stellar configuration can have a mass greater than 5 suns. See, for example, Misner, Thorne, Wheeler, page 627.

The result is a gravitational field at the surface of a neutron star about 70 trillion times stronger than that on Earth.

Given that neutron stars have mass about 500,000 times that of the earth, and radius about 1/400 earth radius, one can use the Newtonian inverse-square law approximation to get a factor of about 80 billion, which is considerably less than your figure. Where did you get these numbers?

Its core consists mainly of densely-packed neutrons, with a sprinkling of protons and typically 3 times as many electrons as protons, in a liquid-like state known as neutronisticis.

Do you have a reference for this? Most models of neutron stars treat the core as a degenerate Fermi gas, and as another poster noted, your star seems to have a net negative charge. Where did the protons go? Also, this is the first time I've encountered the word "neutronisticis". A Google search turns up nothing but this very post.

As a neutron star cools and grows, strains develop in the crust so that it buckles, causing starquakes equal to 1000 on the richter scale.

Starquakes are thought to be possible, but if our time frame is more than a few seconds after formation, the cause is probably not due to thermal stresses. This is because the thermal contribution to pressure and density is negligible as long as the temperature of a neutron star is below the Fermi energy of matter at nuclear density (about 30MeV, or 3*10^11 K - see MTW page 599, referenced above), and neutrino radiation brings the temperature well below this level very rapidly.

The Richter scale is logarithmic, based at 105 Joules for a degree 0 quake (reference), and growing by a factor of 1000 for every two degrees. A quake registering 1000 would have to release 1.05*10^1502 Joules, which is much more than the mass-energy contained in the observable universe. Indeed, it is quite impossible for any stellar-scale phenomenon to register more than 40 on the Richter scale, simply because stars don't have enough mass to release that kind of energy.