| From: veronica | 8/30/01 1:11:58
PM |
| Subject: neutron stars | post id:
395172 |
| I know neutron stars are normal
collapsed stars like our sun, and they are heavy but what would they be
like to land on and of what is it made.? | |
| From: B.C. ® | 8/30/01 2:11:24
PM |
| Subject: neutron stars | post id:
395278 |
| Pete .....found this "In a neutron stars composition, conventional physics produces a gradual transition from ordinary matter[protons, neutrons and electrons]to quark matter[a blob like substance made from unusual combinations of quarks] On the surface is an Iron crust. Below that are superfluid neutrons and other particles that gradually give way to quark matter as depth and pressure increases. At the centre is a pure quark/matter core. Taken from sky and Space magazine By Stephen M Maurer. Now off to work!! | |
| From: Geraint ® | 8/30/01 2:26:12
PM |
| Subject: neutron stars | post id:
395306 |
| Yes, there are limits to the size
of a neutron star - too large and the degeneracy pressure is overcome and
you have a black hole - too small the gravitational mass is not enough for
the electrons and protons to squeeze togther to get neutrons. Note, that
in the neutron star, the neutrons don't decay (in the same way as neutrons
inside an atom don't). | |
| From: Chris (Avatar) | 8/30/01 6:11:37
PM |
| Subject: neutron stars | post id:
395624 |
The surface of a neutron star is generally expected to be "crystalline" "crust". The interior more fluid, consistent with a degenerate gas. I kinda think its hard to get the mind around states of matter under such mind boggling stress! :o) I also think the quark core is a bit speculative, but I'll see if there's been an update before confirming. | |
| From: Greg L. ® | 8/30/01 10:20:36
PM |
| Subject: neutron stars | post id:
395825 |
I know nuetron stars are normal collapsed stars like our sun, and they are heavy but what would they be like to land on Not terribly pleasant-the surface of a neutron star is threaded with extremely strong magnetic fields billions of times stronger than that of Earth's. This magnetic field creates an enormous potential difference that accelerates charged particles at the surface to almost light speed-you would thus get bombarded with a storm of high-energy particles. Neutron stars are also often very hot, emitting mainly in the X-ray end of the e-m spectrum-even a distant observer would get cooked by the synchrotron radiation, which is very energetic and tends to get 'beamed' in a certain direction. In addition to this, the gravitational field near and at the surface of a neutron star is very, very strong-the differences in tidal forces alone between an observer's head and feet ensure they would get ripped to bits in a fraction of a second. Secondly, a accelerating observer would hit the surface at a very high speed at a substantial fraction of light due to the enormous gravitational field near the neutron star. and of what is it made.? A neutron star is made mainly of a degenerate 'gas' of neutrons, hence the name. The surface of a neutron star is essentially made of solid neutron-matter, effectively forming a 'crust.' Below the surface is thought to be a 'sea' of superfluid neutrons, protons and other particles, with the core composition and structure uncertain, but may be a 'soup' of exotic particles such as hyperons, mesons, and 'quark' matter. We are really not sure because matter at this incredible density is hard to model theoretically. | |
| From: Greg L. ® | 8/30/01 10:22:17
PM |
| Subject: neutron stars | post id:
395827 |
How would a photon behave on interaction with a neutron star? The photon would suffer a redshift in its wavelength if it were outbound, and a blueshift if it were inbound. There would also be some gravitational lensing due to the enormous gravity close to the surface. | |
| From: Greg L. ® | 8/30/01 10:24:06
PM |
| Subject: neutron stars | post id:
395830 |
Which would weigh more a teaspoonful of white dwarf, a teaspoonful of red giant or a teaspoonful of neutron star? Neutron star. BTW this sounds like homework-you really should go and get an astronomy book from your local library and find the answers there-it is a lot more fun to read and get the detailed stuff from there, than not doing any work at all and understanding little. | |
| From: B.C. ® | 8/30/01 10:58:01
PM |
| Subject: neutron stars | post id:
395880 |
| Hi Chris, thanks for your
additional info, although a bit hard to understand! I have found an article that I was referring to. It is in this months[August]copy of "Sky and Telescope. Relevant extracts from it are as follows....... The modern picture of a neutron star traces the history like a series of tree rings. At the surface,19th century physics governs. For the few first hundred metres, the neutron star has a crust made of solid Iron. This is because Iron is the end product of nuclear fusion. Since stars cannot burn Iron to produce energy they leave it behind as ash. Beneath the crust things get complicated. For the first two or three kms,1930's physics,Baade and Zwicky's ball of neutrons works well. But deeper still, 21 st century physics takes over. The typical neutron star becomes a complicated mix of neutrons, protons, and electrons. Within three kms of the core some physicists speculate that the density gets so high that the intense pressure forms hyperons. On Earth hyperons are found in particle accelerators, and high energy cosmic rays. Near the cntre of the star hyperons may be the most common form of matter. Another section of the article was in my previous post re quark/gluon soup and "strange matter" The new theories for neutron star composition has come mainly from experiments at the RHIC in New York. | |
| From: John Devers ® | 8/30/01 11:06:14
PM |
| Subject: neutron stars | post id:
395887 |
| Here a bit I found on the
makeup. Hey BC did you see my competition thread? The guts of a neutron star We'll talk about neutron star evolution in a bit, but let's say you take your run of the mill mature neutron star, which has recovered from its birth trauma. What is its structure like? First, the typical mass of a neutron star is about 1.4 solar masses, and the radius is probably about 10 km. By the way, the "mass" here is the gravitational mass (i.e., what you'd put into Kepler's laws for a satellite orbiting far away). This is distinct from the baryonic mass, which is what you'd get if you took every particle from a neutron star and weighed it on a distant scale. Because the gravitational redshift of a neutron star is so great, the gravitational mass is about 20% lower than the baryonic mass. Anyway, imagine starting at the surface of a neutron star and burrowing your way down. The surface gravity is about 10^11 times Earth's, and the magnetic field is about 10^12 Gauss, which is enough to completely mess up atomic structure: for example, the ground state binding energy of hydrogen rises to 160 eV in a 10^12 Gauss field, versus 13.6 eV in no field. In the atmosphere and upper crust, you have lots of nuclei, so it isn't primarily neutrons yet. At the top of the crust, the nuclei are mostly iron 56 and lighter elements, but deeper down the pressure is high enough that the equilibrium atomic weights rise, so you might find Z=40, A=120 elements eventually. At densities of 10^6 g/cm^3 the electrons become degenerate, meaning that electrical and thermal conductivities are huge because the electrons can travel great distances before interacting. Deeper yet, at a density around 4x10^11 g/cm^3, you reach the "neutron drip" layer. At this layer, it becomes energetically favorable for neutrons to float out of the nuclei and move freely around, so the neutrons "drip" out. Even further down, you mainly have free neutrons, with a 5%-10% sprinkling of protons and electrons. As the density increases, you find what has been dubbed the "pasta-antipasta" sequence. At relatively low (about 10^12 g/cm^3) densities, the nucleons are spread out like meatballs that are relatively far from each other. At higher densities, the nucleons merge to form spaghetti-like strands, and at even higher densities the nucleons look like sheets (such as lasagna). Increasing the density further brings a reversal of the above sequence, where you mainly have nucleons but the holes form (in order of increasing density) anti-lasagna, anti-spaghetti, and anti-meatballs (also called Swiss cheese). When the density exceeds the nuclear density 2.8x10^14 g/cm^3 by a factor of 2 or 3, really exotic stuff might be able to form, like pion condensates, lambda hyperons, delta isobars, and quark-gluon plasmas. Yes, you say, that's all very well for keeping nuclear theorists employed, but how can we possibly tell if it works out in reality? Well, believe it or not, these things may actually have an effect on the cooling history of the star and their spin behavior! That's part of the next section. | |