PDA

View Full Version : Strange Quark Matter in Stars: A General Overview



Duane
2004-Dec-10, 07:20 PM
An interesting paper which discusses neutron, quark and other strange stars, what we know about them and how we have used observations to reach some conclusions about them.

Strange Quark Matter in Stars: A General Overview (http://arxiv.org/PS_cache/astro-ph/pdf/0412/0412215.pdf)

I find it interesting to note the most precise mass for a neutron star is 1.44110.00035Sm, which fits nicely with the Chandra Limit for the iron core of a massive star that novaed.

Also from the paper:
Only an outer crust can exist for this kind of compact star, as unbound neutrons are converted to more stable strange quark matter

They also discuss how lower mass neutron stars can form. A short from the paper:


The mass-radius curve shows an instability at the onset of the phase transition to hyperon matter which vanishes once a core of pure hyperon matter is present [9].
Increasing the attraction between hyperons even further, the mass-radius curve changes its characteristics completely: hyperon matter gets absolutely stable and corresponding hyperon stars can become arbitrarily small in radii and mass.

It is interesting that the star gets increasingly stable with hyperon attraction, which would seem to absolutely rule out any release of energy from the object.

blueshift
2004-Dec-12, 05:22 AM
Thanks for the reference Duane..

The stability of strange quarks I do know comes from the conservation of strangeness and I didn't really give much thought about a strange quark star's
existence...

Are you guessing that there might be a possibility that we are beginning to see a
greater variety of neutron stars with different origins?

Or, do you think we might be looking at some time keepers of the universe that might tell us information on a precise age/phase sequence in degenerate stars?

blueshift

Duane
2004-Dec-14, 02:58 AM
Originally posted by blueshift@Dec 12 2004, 05:22 AM
Are you guessing that there might be a possibility that we are beginning to see a
greater variety of neutron stars with different origins?

Or, do you think we might be looking at some time keepers of the universe that might tell us information on a precise age/phase sequence in degenerate stars?

blueshift
No, I think we are beginning to understand how the gravity field of these very weird objects affects the atoms that make them up. They all seem to arise in much the same way, that is the collapse of the 1.4 Sm iron core into this strange, unimaginably tightly packed object.

As for time keepers--I wouldn't think so. While we can probably figure out the amount of time it would take a neutron star to radiate away all of its left-over heat energy, they problem is that they can reheat by accretting material as they pass through the ISM. This would throw off any calculations you made.

GOURDHEAD
2004-Dec-14, 12:26 PM
... hyperon matter gets absolutely stable and corresponding hyperon stars can become arbitrarily small in radii and mass.
I'm not surprised by the shrinking radii, but shrinking mass? Are the the quarks being transformed to photons? Not that it matters much after matter has collapsed into quarks, was iron the heaviest atom in the remnant during collapse?

Duane
2004-Dec-14, 02:58 PM
Good question Gourdhead. Perhaps the amount of energy required for the NS to form hyperon matter causes a loss of mass? I'll see what I can find out.

Prime
2004-Dec-15, 01:46 AM
We have now a comparison theory, the Plasma-Electric Cosmos.

Actually there is no comparison, as this is the direction vector of the future.

edit

A revolution is speeded up

Prime

antoniseb
2004-Dec-15, 03:13 AM
Originally posted by Prime@Dec 15 2004, 01:46 AM
the Plasma-Electric Cosmos
Thanks Prime, we'd like to have any further electric universe discussion related to this thread continued in the Electric Universe Thread in the Alternative Theories section.

Duane
2004-Dec-15, 05:32 PM
Prime, I read that link, and what a load of baloney.

If you want to discuss EU theory, there is a thread in the alternative theories section just for you. If I see you post in support of your pet theory in contravention of Rule 6 of these forums, I will delete it without further warning or explanation.

You have been asked not to do this previously. This is the last time you will be warned.

Mild mannered
2004-Dec-15, 05:53 PM
Originally posted by Duane@Dec 14 2004, 02:58 PM
Good question Gourdhead. Perhaps the amount of energy required for the NS to form hyperon matter causes a loss of mass? I'll see what I can find out.
Hey Duane - I'm a Layman - really I know nothing about this level of exotic object but can I ask - when these Neutron stars blast off huge bursts of Gamma rays and Xrays - do they drop mass that way? - surely any kind of energy release related to objects like this (as I've red) will reuce the mass.

How much mass loss are you looking at?

And what of Ferg's Magnetars?

Mild

Duane
2004-Dec-15, 06:09 PM
I have an explanation about the loss of mass, however I hope a real physicist will look and correct any mistakes. (Hello Tim, you out there?)

With regard to hyperon matter, hyperons are a form of baryonic matter that actually has more mass than either a proton or neutron. Hyperons normally decay very quickly (on the order of ~2 x 10^-8 seconds), resulting in a proton or neutron, plus a smaller particle, like a pion.

Now, here's the hard part.

I think it is the case that when ordinary matter ungoes the pressure and energy arising from a supernova, there is the opportunity for hyperons to be made. This process would seem to need one hell of alot of energy, given that the normal nuclei needs to have a small liberated particle driven into it to give rise to the hyperon.

As the hyperon is more massive than the proton or neutron, the resulting input of energy converts some of the energy into mass (E=mc^2 again), which creates a small particle that is incorporated into the nuceli. This energy originally arose when a proton or neutron was converted back into quark matter, releasing energy and decreasing mass. The increasing particle size (the hyperon) captures that energy while at the same time reducing the overall mass and size of the neutron star matter. As more and more hyperons are created and stabilize, the neutron star shrinks and loses its mass to these more massive baryons.

Ouch, my brain hurts! I hope I have this right.

Duane
2004-Dec-15, 06:21 PM
when these Neutron stars blast off huge bursts of Gamma rays and Xrays - do they drop mass that way? - surely any kind of energy release related to objects like this (as I've red) will reuce the mass.

Sure you can ask Mild, big question is, can I answer! ;) I am also a layman, but I am learning like mad.

Short answer to your question is yes, but it has no effect on the neutron star remnant. The original force of the supernova converts some of the original star's mass into energy, but the neutron remnant at the centre is already formed by then.

If you're interested, try searching Type II supernovas on the internet for an explanation on how the neutron remnant forms.

advisor7
2004-Dec-15, 09:36 PM
I welcome you to the forum, but I had to delete this post for two reasons. First, we like to stay on topic, and this comment is not about neutron stars.

2nd, except in the Alternative Theories area, we do not allow promotion of alternative theories in this forum.

Please read the Rules, located here: http://www.universetoday.com/forum/index.p...?showtopic=1134 (http://www.universetoday.com/forum/index.php?showtopic=1134)

Thank you!

Duane
2004-Dec-29, 07:42 PM
By the way, for anyone interested, Tim PM'ed me to advise that he felt I was generally correct in my description of hyperion matter creation in the neutron star. A caution however, Tim is not a particle theorist, so someone who was would be the best person to answer.

Duane
2004-Dec-30, 11:04 PM
This is a parallel study regarding neutron star matter:

Rotating compact stars with exotic matter (http://arxiv.org/PS_cache/astro-ph/pdf/0406/0406315.pdf)

Essentially, they discuss the Equation of State calculations for the formation of very fast rotating compact stars.

Note the paper is only 8 pages long, with another 10 or so pages of equations.