The tag has no wiki summary.

learn more… | top users | synonyms

7
votes
3answers
840 views

Is it possible that black holes are also neutron stars, but so dark that we cannot see them?

Since the concept of the singularity in a black hole leads to infinite densities, I wonder if it is really certain that black holes exist? Is there a possibility that massive objects (which are ...
5
votes
1answer
86 views

Upper Mass Limit of Quark Stars

While there is no confirmation that quark stars exist, is there any theoretical limit analogous to (but different from) the Tolman–Oppenheimer–Volkoff limit for neutron stars? In other words, what is ...
19
votes
4answers
2k views

Can there be Electron and/or Proton Stars?

What happens to all of the electrons and protons in the material of a neutron star? Could there ever be an electron star or a proton star?
2
votes
0answers
23 views

Did cosmological natural selection get a reprieve? [duplicate]

The March 2014 issue of Physics Today has an article by Lee Smolin in which he argues that natural laws must change over time. As examples of such theories, he gives Penrose's CCC and his own ...
25
votes
5answers
4k views

How come neutrons in a nucleus don't decay?

I know outside a nucleus, neutrons are unstable and they have half life of about 15 minutes. But when they are together with protons inside the nucleus, they are stable. How does that happen? I got ...
2
votes
1answer
121 views

Is there a connection between exclusion principle and the speed of light?

As far as I know exotic stars are composed of degenerate matter created by the balance between gravity and pressure of exclusion principle and as the mass of the star grows it goes into more ...
8
votes
1answer
75 views

Will a black hole eventually turn into a neutron star?

As far as i understand, black holes radiate away energy in form of Hawking Radiation. Thus, they lose mass, i suppose. Is there a point where the mass becomes too small for the object to still be a ...
17
votes
7answers
3k views

Why do neutrons repel each other?

I can understand why 2 protons will repel each other, because they're both positive. But there isn't a neutral charge is there? So why do neutrons repel? (Do they, or have I been misinformed?) The ...
6
votes
3answers
1k views

How do neutron stars burn? Is it decay or fusion or something else?

What makes a neutron star burn, and what kind of fusion/decay is happening there? What is supposed to happen with a neutron star in the long run? What if it cools, then what do the degenerated matter ...
-1
votes
1answer
57 views

Quick question on ideal gas law

I know that the ideal gas law is: $$P = nkT$$ So Pressure = Number of Particles per unit volume * kT Why is the number of particles per unit volume = $\frac{\rho}{\mu M_H}$? Shouldn't it simply ...
0
votes
1answer
46 views

What happens to atoms in extremely strong electromagnetic fields?

I know that strong gravitational fields on the order of neutron stars (at the crust) atoms get compressed so tightly, the empty space between them is significantly reduced and it becomes denser. ...
3
votes
2answers
81 views

Smolin on Cosmological selection and neutron stars

Regarding the cosmological selection hypothesis and testable predictions, Lee Smolin asserted the following: "Smolin: I did make two predictions which were eminently checkable by astrophysical ...
7
votes
2answers
293 views

Neutron stars and black holes

The official limits for a neutron star is $1.4 - 3.2\;M_\odot$. But I read that the limit depends on the particular structure of a star to estimate which mass it must have. I also read that neutron ...
3
votes
3answers
160 views

Magnetic Pole Emission from Pulsars

I've been reading up on some pulsar emission theory (admittedly written in the 70's and 80's, but I figured that's a good place to start), namely this review by Curtis Michel as well as the book Black ...
6
votes
3answers
408 views

What allows the modified Urca process to work at lower density than direct Urca in neutron star cooling?

The dominant method of neutron star cooling is neutrino emission. There are two regimes usually presented, the "direct Urca" and "modified Urca" processes, each of which are sequences of neutron decay ...
11
votes
3answers
692 views

What stabilizes neutorns against beta decay in a neutron star?

Free neutrons are known to undergo beta decay with a half-life of slightly above 10 minutes. Binding with other nucleons stabilizes the neutrons in an atomic nucleus, but only if the fraction of ...
6
votes
3answers
477 views

Do neutron stars reflect light?

The setup is very simple: you have a regular ($1.35$ to $2$ solar masses) evolved neutron star, and you shine plane electromagnetic waves on it with given $\lambda$. Very roughly, what shall be the ...
3
votes
1answer
31 views

What compact central objects younger than the crab pulsar have been seen?

We see the crab pulsar, we don't see any compact remnant from Supernova 1987A. I can't find any others, but I believe they exist. Help?
41
votes
8answers
1k views

Do all black holes have a singularity?

If a large star goes supernova, but not enough mass collapses to form a black hole, it often forms a neutron star. My understanding is that this is the densest object that can exist because of the ...
2
votes
4answers
1k views

If there were no space between nuclei, how big would the Earth be?

I have some people telling me it would be the size of baseball. I am quite doubtful on this. If this is true, then the gaps must be so incredibly huge that everything should be transparent. I am not a ...
9
votes
1answer
255 views

How would neutron matter appear to the naked eye?

Neutron matter is matter comprised entirely of neutrons, as it exists in neutron stars. Most optical phenomena encountered in everyday life, such as light reflection and spectral absorption (i.e. ...
9
votes
1answer
122 views

Are the neutrons in a neutron star on orbitals as in atomic nuclei?

Does the internal structure of a neutron star resemble anything like that of an atomic nucleus? I.e., are the neutrons arranged in a shell like structure with different energy levels, and without a ...
7
votes
1answer
1k views

What happens to atoms inside a black hole?

Black holes have very high gravitational force that tends to crush everything. So as we know atoms in a molecule have inter-atomic spacing between them and further electrons also revolve at a certain ...
14
votes
3answers
1k views

Is it possible that all neutron stars are actually pulsars?

I'm assuming that what I've been told is true: We can only detect pulsars if their beams of electromagnetic radiation is directed towards Earth. That pulsars are the same as neutron stars, only that ...
10
votes
2answers
290 views

Stellar winds from neutron stars

It seems that this question has not really been explored in the literature. Do isolated neutron stars (which do not accrete material) emit stellar wind? If yes, what composition would it have? If yes, ...
2
votes
1answer
113 views

What is the difference between baryonic and gravitational mass?

I was reading a webpage on neutron stars, and it mentioned that a neutron star's gravitational mass is about 20% lower than its baryonic mass due to gravitational redshift. I understand the basics of ...
6
votes
2answers
218 views

How to cut a stone on on a White Dwarf

I've heard that white dwarfs are extremely dense and hard. So, if I had a piece of white dwarf matter, would it be possible to cut it (or otherwise) into a custom shape? How could one do that?
10
votes
2answers
605 views

Black Hole Photon Sphere

The photon sphere is a spherical region in space where photons are forced to travel in an orbit at $r = \frac{3GM}{c^{2}}$. Is it possible to detect these spheres? What happens if I fall through ...
6
votes
1answer
70 views

What is baryon loading in the context of gamma ray bursts (GRBs)?

I've read that with short hard gamma ray bursts (shGRBs) associated with the coalescence of NS-NS and NS-BH binaries are expected to be beamed along the axis of the orbital angular momentum (i.e. ...
0
votes
1answer
51 views

Conversion of a star

I need to know what would happen to a star that has size 2 times the solar mass. I guess it would either be a neutron or red giant. Is that right?
4
votes
2answers
307 views

What is the temperature of the surface and core of a neutron star formed 12 billion years ago now equal to?

In what part of the spectrum is it radiating? In the infrared, in the microwave? Or is not radiating anymore at all? In russian: Чему сейчас равна температура поверхности и ядра нейтронной звезды, ...
11
votes
3answers
301 views

Are Neutron stars transparent?

Neutrons have no charge so they would not, I think, interact with photons. Would a neutron star be transparent?
14
votes
1answer
981 views

Turned to steel in the great magnetic field

This is obviously a "fun" question, but I'm sure it still has valid physics in it, so bear with me. How great of a magnetic field would you need to transmute other elements into iron/nickel, if ...
4
votes
2answers
184 views

Is Brian Cox right to claim that Gravity is a strong force for large masses, is it wrong, or is it only a matter of interpretation?

I watched a program of his in which it was claimed that since mass bends space in accordance to General Relativity, then in the case of very large stars it becomes a strong force to the point of being ...
1
vote
1answer
519 views

Neutron star material

I've read on NASA's page on neutron star that one teaspoonful of that star would weigh over 20 billion ton on Earth. If it was somehow possible to bring it to earth would it: A) Burn and disappear ...
3
votes
1answer
558 views

Collision between Neutron stars and Black holes

When two neutron stars or black-holes come closer and closer, their angular velocity increases with decrease of distance and they start to revolve around a constant center with high relativistic ...
0
votes
1answer
79 views

Regarding binary systems

Are binary systems (in case of stars and other celestial bodies) more favorable than independent existence? I've been going through an article regarding pulsars, where it was stated that 'many pulsars ...
2
votes
1answer
146 views

In a neutron star - what force keeps the neutrons from getting closer and closer? [duplicate]

Possible Duplicate: Why do neutrons repel each other? What I mean is that the neutrons are attracted to one another via gravity, so what force keeps them from collapsing to form a "neutron ...
0
votes
1answer
81 views

Gravity and Magnetism on Stars

I am familiar with the fact that Magnetars have a really strong magnetic field and an ordinary star such as the Sun has a very strong gravitational field. But what about the opposite? What is the ...
1
vote
2answers
216 views

Can a neutron star compress until it's converted to a black hole?

The Universe's densest objects are black holes. In the second place, there are neutron stars. So, if a neutron star compresses to its Schwarzschild radius, would it appear as a black hole? That black ...
3
votes
1answer
177 views

Compressing a fluid with arbitrarily large force in an infinitely strong chamber

Imagine I have an infinitely strong container of volume $v_1$, and I fill it with some monoatomic fluid like liquid hydrogen. I then proceed to compress the walls of the container to reduce its ...
8
votes
2answers
146 views

What causes millisecond pulsars to speed up?

Millisecond pulsars are supposed to be old neutron stars. However, they are spinning even more rapidly than newly formed pulsars. Since pulsars slow down as they age, something must have caused ...
10
votes
1answer
168 views

Introduction to neutron star physics

I enjoy thinking about theoretical astrophysics because I want to understand black holes. Given that no one understands black holes, I like to ponder the nearest thing to a black hole: a neutron star! ...
6
votes
1answer
68 views

Could a neutron star be active, fusioning neutrons into something more dense and releasing constant power?

Could a neutron star be a bit like our Sun or any other star? Just to have a different scale: A neutron star fusioning not hydrogen and other elements but neutrons and quarks in its core at a ...
3
votes
2answers
171 views

Are there any known neutron stars just below the Tolman–Oppenheimer–Volkoff limit?

Do we know any neutron stars just below the Tolman–Oppenheimer–Volkoff limit? And how are they different from most other neutron stars?
11
votes
3answers
1k views

If I shine a bright light on a neutron star, what would it look like?

If there are no orbitting electrons in a neutron star's makeup to interact with EM, what happens to light that strikes it?
10
votes
0answers
41 views

What allows the modified Urca process to work at lower density than direct Urca in neutron star cooling? [duplicate]

Possible Duplicate: What allows the modified Urca process to work at lower density than direct Urca in neutron star cooling? This comes from an unanswered question over at physics.se: The ...
4
votes
2answers
181 views

What is a magnetised neutron star?

I heard the term the other day, but it seems strange to me. My understanding is that neutron stars are made up of neutrons; and neutrons (having no charge) shouldn't be magnetised.
3
votes
3answers
127 views

Neutron star references?

I'm looking for contemporary reviews on neutron stars. Seems like this area is pretty active, so even reviews from five or ten years ago are somewhat lacking, though certainly not worthless. Does ...
3
votes
1answer
357 views

neutrinos by formation of “neutron pairs”

Here : http://www.newscientist.com/article/dn20084-neutron-star-seen-forming-exotic-new-state-of-matter.html are news on superfluidity in a neutron star. The necessary bosons they say are pairs of ...