Talk:Neutron star
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Question: what is the internal structure of a neutron star like? Where are the boundaries between neutronium, degenerate and normal matter located? What percentage of the stars mass or volume are each? What is degenerate matter? What do the boundaries between the layers look like? What is there shape? (I suppose some of these questions may not have answers yet...) -- SJK
I can answer some of these questions...
From what I've read, neutron stars don't have any internal structure. It's just neutrons, all the way through. The degenerate and normal matter layers are just a few meters thick on the surface. So it's something like 99.9% plus percent of the star's mass is neutrons. This is because nothing else can possibly exist inside there.
It's wierd to think about them. A neutron star is essentially a titanic atomic nucleus, which is held together by gravitational force instead of the weak nuclear force. -- The_ansible
As I corrected in the article, a neutron star is not like an atomic nucleus, because it is not just protons and neutrons, but almost all neutrons inside and whatever on the surface (assuming you're correct in that notion).
Also I think you meant the residual strong force, the weak force is the mediator of beta decay, the breaking up of neutrons into electrons etc., the opposite of what happens in a neutron star. Rmrfstar 00:36, 5 Apr 2005 (UTC)
Whoever deleted the term 'neutronium' from the main page -- if you are saying not to use that term, note we already have a page neutronium. Secondly, I find your new version hard to follow -- whats an 'iron layer'? Finally, but 'quark matter' you mean what? -- SJK
- more on neutronium - http://www.physics.uq.edu.au/people/ross/ph227/evolve/whitey.htm
- "quark matter" is probably a reference to strange matter
Sorry, it was made in a haste. Iron layer is a thin crust of metalic iron, by quark matter i mean a soup where not even individual neutrons exist, but a mixture of quarks of different kinds. "strange" matter is matter partially composed by "strange" quarks. What i tried to emphasize is that there was a comtinuum of compositions inside a neutron star, and that telling "a crust of degenerate matter and and interior of neutronium" was an oversimplification that also hided the fact that there is no aggreement respect to what's in the core. AN
Ok. i can live with that for the time being. AN
- You see - we actually can all get along :) - MMGB
From the article:
- "When neutron stars were first discovered, they were believed to be evidence of extra-terrestrial intelligences. Because of their highly regular pattern of emmisions, they were initially though to be beacons of some type."
I don't think that pulsars were ever seriously thought to be evidence of extraterrestrial intelligence, at least not by the researchers who were actually investigating them. The first pulsar discovered was dubbed "BEM-1" (Bug-Eyed Monster 1) as a joke by its discoverers, if I recall correctly. But since this is all from memory, anyone have any references handy? Bryan Derksen
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As a non-physicist, how does this sentence:
- Neutron stars are the densest objects known
relate to black holes? Thanks, [[User:Meelar|Meelar (talk)]] 19:04, Sep 10, 2004 (UTC)
I'm not well read in astrophysics, but mass and [density] are two separate things. Compare traffic in New York to traffic in California. New York has tons of traffic jams and everyone is stuck together. California might have more cars overall, but they're more spread out for the main part. The same is true for black holes and neutron stars, black holes have more mass, but neutron stars are more closely packed. Presuming the statement above is correct. If anyone more knowledgable can confirm this that would be good.
I believe you are correct in your distinctions between mass and density, however I think a black hole is still infinitly dense, even if you determine it's size by it's Schwartzchild radius. Rmrfstar 00:38, 5 Apr 2005 (UTC)
Rate of rotation slow down?
The article specifies slow down rates that appear far, far too small (10-12 and 10-19 second for each century), in fact too small to logically produce the older slower-rotating stars within the universe's current age the article also mentions. Googling around, I see zebu.uoregon.edu (http://zebu.uoregon.edu/~js/ast122/lectures/lec19.html) has "about 10-15 seconds per rotation", so I suspect "per century" should be changed to "per rotation", and this would change the next sentence as follows, for a star initially rotating at 1 second: In other words, a neutron star now rotating in 1 second will rotate in 1.000003 seconds after a century, or 1.03 seconds after 1 million years. Does this look sensible? -Wikibob | Talk 22:49, 2005 Apr 19 (UTC)
- This is kind of true, however generally the spin-down rate (period derivative) is expressed in dimensionless units, or if you want to think of it that way, seconds per second (=rotations per rotation). What you've said is kind of true since most observable neutron stars have rotation periods of the order of 1 second. However, on that point, both the spin period AND the period derivative are very much dependent on the type of neutron star (i.e. its history and present circumstances). So probably the whole paragraph needs to be generalised a bit, and the specific numbers and info left to the appropriate sub-articles. Rotation-powered pulsars spin down via magnetic dipole radiation, so their spin down rate depends on their magnetic field strength. The range you quoted is roughly valid for ordinary rotation powered pulsars, which have periods of mainly about 0.1-5 seconds. Recycled rotation powered pulsars otoh have periods of 1-100 milliseconds and spin down rates of 10-21 - -17, while magnetars have periods around 10 seconds spin down of 10-12 - -10. Accreting neutron stars OTOH vary in spin period due to the transfer of angular momentum from the accretion stream, so this can be spinning up or down and can vary with time, and have spin periods up to many 10s of seconds. All this is IMO too much detail for the top level neutron star entry (but I don't have time at the moment to improve it myself). Rkundalini 07:07, 21 Apr 2005 (UTC)
Effects of superstrong magnetic fields
The Neutron star article states:
"Another class of neutron star, known as the magnetar, exists. These have a magnetic field of above 10 gigateslas, strong enough to wipe a credit card from the distance of the Sun and strong enough to be fatal from the distance of the Moon. By comparison, Earth's natural magnetic field is 50 microteslas, and on Earth a fatal magnetic field is only a theoretical possibility; some of the strongest fields generated are actually used in medical imaging. A small neodymium based rare earth magnet has a field of about a tesla, and most media used for data storage can be erased with milliteslas."
The Magnetar article states:
"A magnetic field above 10 gigateslas is strong enough to wipe a credit card from half the distance of the Moon from the Earth1. A small neodymium based rare earth magnet has a field of about a tesla, Earth has a geomagnetic field of 30-60 microteslas, and most media used for data storage can be erased with a millitesla field.
The magnetic field of a magnetar would be lethal at a distance of up to 1000 km, by warping the atoms in living flesh2."
The two don't agree too well, though they are clearly derived from similar source material. Maybe someone who knows which version is correct can fix the incorrect one? Thanks!--Ailicec 01:18, 7 Jun 2005 (UTC)
- Wouldn't the iron in your blood be affected, Xmen style, before the "atoms in living flesh" were warped? If that statment is untrue it would detract from the credibility of the 1000km statement. Rmrfstar 21:30, 19 May 2005 (UTC)
- The main point being that at least one of them is wrong. ((btw, added my sig to original question, I didn't know how to do it when I wrote that) --Ailicec 01:18, 7 Jun 2005 (UTC)
Ionized electrons?
"The matter at the surface of a neutron star is composed of ordinary nuclei as well as ionized electrons." Surely the person writing this meant "ionized atoms" eg ions?