Matt

I knew that I should have been an astronomer, this stuff is just way too cool!


<a href="http://www.cnn.com/2002/TECH/space/04/10/new.matter/index.html" target="_blank">Strange stars suggest new kind of matter</a>

fando

New kind of matter? Damn media... that should be "form".

By the way, the jury is still out on the properties of these stars. They could also be made of other pixie particles that make up the standard model zoo.

Anyhoo, some more links:

<a href="http://chandra.harvard.edu/photo/2002/0211/index.html" target="_blank">
Basic info at Harvard</a>

<a href="http://www1.msfc.nasa.gov/NEWSROOM/news/releases/2002/02-082.html" target="_blank">
NASA press release</a>

<a href="http://xxx.lanl.gov/abs/astro-ph/0204159" target="_blank">
Actual preprint at xxx.lanl.gov</a>

fando

According to the preprint, the possibility of a "strange star" made up of strange quarks was presented back in 1986. The signature of such a star was calculated in 2001 and now we have two candidates that match the predictions. They'll need to find a few more candidates to actually be sure.

This is certainly a significant find. My Astronomy textbooks on stellar evolution are now out of date.

Matt

fando,

Thanks for the links. I printed the preprint of the article for the Astrophysical Journal and will read it this weekend.

Coragyps

From the Chandra/Harvard link: Wow. I had seen something in Sky and Telescope about the prediction of these. Who was it that said "The Universe is not only stranger than we imagine, but stranger than we can imagine"?

Shadow Wraith

Interesting, but debateable. Here's another person's thoughts on the idea:
<a href="http://www.holoscience.com/views/view_strange.htm" target="_blank">http://www.holoscience.com/views/view_strange.htm</a>

[ April 12, 2002: Message edited by: Shadow Wraith ]</p>

Freethinking Ferret

Well, I'm not going to go into an in-depth refutation of the statements on that page, Wraith, for the simple fact that I'm not educated enough in the field of astro/particle physics... however, the page is 2 years out of date; while this may seem like a very small period of time, many giant steps have been made in astrophysics over the past couple of years.

For example, the author mentions the solar neutrino problem in his comments to point 3:

3. It is assumed that we understand how our Sun and other stars shine, evolve, and someday die or form neutron stars.

We do not understand... low neutrino count, etc.

A solution to this problem has been presented through work done at the <a href="http://www.sno.phy.queensu.ca/" target="_blank">Sudbury Neutrino Observatory</a>, and it certainly seems that observations fit the theory and support the current stellar model, at least in this area.

As well, in response to point 2:

No book on astronomy mentions electrical effects.

No book, in the history of the study of astrophysics, mentions electrical effects? EM doesn't play some role in some part of astrophysics research, somewhere in the world?

Finally:

And particle physicists who are trying to work out how the universe was constructed from strange matter early in the Big Bang are wasting their time. The astronomer Halton Arp, author of the Atlas of Peculiar Galaxies, has conclusively disproven the theory of an expanding universe and so knocked out the foundation of the Big Bang theory.

That's right, theoretical physicists the world over, you'll have to find yourselves new jobs, the mystery has been solved!

(edited to fix url)

[ April 12, 2002: Message edited by: Freethinking Ferret ]</p>

Coragyps

Yow! I knew Arp had some issues with the standard ideas on redshift, but this is sorta strong language....

lpetrich

One problem with detecting a quark star is that its outwardly-apparent properties are expected to be much like those of a neutron star -- similar range of masses, radii, etc.

Here is why the two putative quark stars have been identified as such:

RXJ1856 (400 lyr, Corona Australis) is identified as one because it is something like half the size that a neutron star is expected to be, judging from its temperature and luminosity.

3C58 (10,000 lyr, Cassiopeia, observed as supernova in August 1181 in China and Japan) is identified as one because it has cooled off faster than expected for a neutron star; its surface temperature is too small by a factor of 2.

However, there are various theoretical difficulties; RXJ1856 may have a "hot spot" that causes trouble with the estimate, and the cooling rate of a neutron star is rather difficult to calculate precisely.

Degeneracy pressure is what produces the shape of every object not hot enough for thermal pressure to do so. Here is how it happens:

Particles with half-odd spins like electrons (spin 1/2) follow Fermi-Dirac statistics, meaning that only one can occupy a quantum state at a time. Those with integer spins follow Bose-Einstein statistics, meaning that any number can occupy a quantum state at a time.

If one puts electrons into an electron-impermeable box and keeps them cold, the first one will enter the lowest possible state, the ground state. The second one also enters the ground state, but with opposite spin. The next one enters at the next state up, and the next one at that state, but with opposite spin. Etc.; the electrons gradually pile up and get into higher and higher states, thus shorter wavelengths and greater momenta.

Familiar physical objects get their shape and properties as a result of degeneracy effects and electrostatic interactions among electrons and nuclei; as one adds electrons to nuclei, they fill sets of quantum states or shells; something can be seen from the Periodic Table of Elements.

Most atoms' electrons are localized in the atoms; some outer ones may be shared with neighboring atoms, producing a chemical bond, and some outer ones may not be localized and instead wander around, producing a metal.

If one crushes a familiar material enough, outside pressure will compete with electrostatic effects, and at a high-enough pressure, its outer electrons will become less constrained by the nuclei, and the material will become metallic, something observed for hydrogen.

And with sufficient pressure, the nuclei can become overwhelmed, thus producing a kind of degenerate electron gas. White dwarfs are composed of this.

Crushing even further will force the electrons to react with protons, forming neutronium, something like an atomic nucleus with mostly neutrons. These are spin-1/2, like electrons, meaning that they produce degeneracy pressure. But these particles rather strongly resist being squeezed below a certain size; exactly how much is difficult to determine, causing serious uncertainties in neutron-star structure estimates.

Protons and neutrons (nucleons) contain three quarks that interact with gluons; however, this interaction is very strong, making calculations difficult.

Protons are up-up-down, neutrons are up-down-down.

And now for what a quark star is supposed to be. If compressed enough, nucleons may lose their separate identities and become one big quark/gluon soup. Also, some down quarks may change to strange ones, producing a "strange star". Quarks are also spin-1/2, and they also produce degeneracy pressure. But they interact very strongly with gluons, complicating the calculations.

So what's a neutron star and what's a quark star will continue to be a difficult question.

lpetrich

As to Halton Arp, his admirers defend him as a latter-day Galileo, someone persecuted by orthodox astronomers who refuse to take his observations seriously.

He is the author of an Atlas of Pecular Galaxies, and in the process of compiling that atlas, he discovered some galaxy-quasar associations. However, these associations may simply be line-of-sight coincidence; Arp has yet to provide a clear case that he is seeing too many to be coincidence.

And even if there are too many to be coincidence, here's an effect that could create it: amplification by gravitational lensing caused by the galaxy or one of its stars.

Arp has griped that he has been denied telescope time, which makes him seem like some Galileo-ish martyr to his supporters. But being martyred does not mean that one is right.

The implication of Arp's findings is that quasars are not at the great distances that their redshifts imply that they are at; instead, that they are at the distances of those nearby galaxies, with their redshifts coming from somewhere else.

This would help solve the problem of why quasars are so bright -- nearby ones would be dimmer -- however, the redshifts are difficult to explain. Are they all moving away from us? Why is there no heavily blueshifted one moving toward us? And for the redshift to be due to gravity means that quasars are very close to being black holes, which is also asking a bit much. One old redshift hypothesis is the "tired light" hypothesis, that traveling light somehow gets drained of energy, and thus redshifted. But why would it work on a quasar but not a nearby galaxy?

So unlike the case of Galileo, Arp's critics have some very strong arguments.