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Quark Stars
BigGar' writes "Astronomers seem to have discovered a new type of star. It would lie between a neutron star and and a black hole in the hierarchy of stars and consist of quark matter. Further observations with the Chandra X-ray telescope will be needed to confirm the results."
Does anyone know if all up quarks are the same as all other up quarks...
Well the up quark, like any quark, is not as cleanly defined as the word "particle" might indicate. The up quark and the properties associated are not just a measure of how much "mass" or "spin" has been shoved into a sphere called the quark. The properties of quarks actually come from an extremely complex cloud of virtual particles that pop into and out of existence in close proximity to the area we call the quark. There seem to only be a few stable configurations of energy, spin, and charge that can result in a quark. The properties of the quarks seem to result from some intrinsic properties defining the way these virtual particles can interact, so you can't just put a little more of something into a quark, because that would require changing the rules of the interactions. Unfortunately, the precise details of all of the above is still a subject of some speculation, since no one quite knows for sure all the virtual particles that can pop in and out and all of their properties.
I am one of the authors of a competing paper on RX J1856 that was published yesterday, as well as a co-discoverer of the pulsar in 3C58. In my opinion these results, while definitely a possibility are certainly very preliminary. And in fact, there are other possibilities that make quite a bit more sense.
In the case of RX J1856, there is a ~15% chance that the lack of pulsations (one of the biggest reasons for suspecting a quark star) is simply the result of an unfortunate emitting geometry or viewing alignment. Given that there are ~7 objects known that are similar to RX J1856, having at least one of them in this 15% seems quite likely to me -- and avoids having to invoke a new form of "star stuff".
As for 3C58, the neutron star cooling problem can be mitigated (but not completely removed) by assuming a larger age for the supernova remnant (and therefore the neutron star) -- which expansion measurements and pulsar timing measurements also suggest.
In other words, there are simpler explanations for the facts. Although those explanations certainly wouldn't get as much press...