Questions tagged [neutron-stars]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
4
votes
1answer
85 views

Can gravity give neutrons a longer lifespan? [duplicate]

Isolated neutrons have a lifespan of about one minute yet neutrons in a neutron star can have the lifespan of the neutron star itself and not decay into proton and electron. Is the intense gravity ...
0
votes
2answers
194 views

Gravitational Time Dilation Inside a Massive, Non-Uniform, Non-Rotating Sphere

I know the time dilation (relative to an observer at infinity) outside a non-rotating sphere can be found from the Schwarzschild metric to be $$t_{0}=t_{f}\sqrt{1-\frac{r_{s}}{r}}$$ where $r_{s}$ is ...
-1
votes
5answers
121 views

How does gravity acts on the electrons to collapse a neutrons star or white dwarfs against the degeneracy pressure?

if electrons is considered as quantum particle in case neutron star (alluding to quantum statistics) how does gravity makes the star collapse? considering the fact that electrons are quantum particles ...
0
votes
1answer
39 views

Question about nuclear reation

In Landau and Liftshitz Volume 5 page 318, it talks about nuclear reaction in high density, where proton reacts with electron and becomes neutron and neutrino: $$A_z+e^- = A_{Z-1}+\nu$$ where $A_z$ ...
1
vote
1answer
78 views

Is there a Neutron Star or Black Hole close to solar system?

I recently read an article where it mentioned that the solar system could be born out of a supernova explosion (death of a previous star). In case there was a supernova, wouldn't there be a ...
-1
votes
1answer
66 views

Why are neutron spectra continuous, with maxima? e.g 252Cf [closed]

I want to know why there is a maximum and then decrease.
3
votes
2answers
232 views

How does a neutron star collision turn mass into gravitational waves?

I heard on the TED Radio hour that in the neutron star collision that LIGO recently detected, some of the mass of the neutron stars was turned into energy in the form of gravitational waves. How does ...
2
votes
3answers
279 views

What is the roundest object in the universe?

I would imagine it to be something that has a few of the following characteristics: held tightly together by gravity. large, relative to the deviation of its topography. has minimal spin. I Googled ...
0
votes
1answer
41 views

Is the R-process the only mechanism for making heavy elements in a neutron star merger?

Is it possible that in the debris field left over from a neutron star merger (kilonova) there are heavy element sized chuncks of (mostly) neutron matter that undergo rapid beta-decay to become the ...
2
votes
1answer
295 views

What is the speed of light escaping a neutron star? [duplicate]

If the escape velocity of a neutron star is just less than that of light, will light come out very slowly from the star?
2
votes
0answers
56 views

Observational evidence for superfluidity in neutron stars

What is the earliest evidence for the existence of superfluidity in neutron stars? I'm about to present the subject in a seminar and I'm under the impression that at the moment there is no ...
7
votes
1answer
253 views

Would dark matter (as a BEC) be captured by Black Holes, Neutron Stars, etc?

Suppose that dark matter is in the form of a Bose-Einstein Condensate, with a DeBroglie wavelength of ~10,000 LY. (There are some axion models of DM where the axions are in a BEC.) In this model, the ...
2
votes
0answers
68 views

What would happen if very light particles (of large de Broglie wavelength) encountered a neutron star?

I want to consider the possibility of a very light particle being captured by a neutron star. (For the purpose of discussion, let us allow the neutron star mass (or radius) a tunable parameter, so ...
-1
votes
2answers
63 views

Neutron Stars of unequal mass merging

Is the difference in masses between merging Neutron Stars the cause of the massive gravitational disturbances due to the unbalanced decaying orbit right before the merger?
0
votes
0answers
20 views

Could quark star becomes a neutron star? [duplicate]

Fusion of quarks release 8 times more energy than hydrogen fusion, so I was wondering if quark star exists and before quark degeneracy pressure kicks in wouldn't these tightly packed sea of quarks ...
-3
votes
2answers
207 views

How many neutrons are there in a teaspoonful of a neutron star and if stacked end on end, how far would these neutrons reach? [closed]

I am not a physicist nor a student of physics. I am just an old man that wonders. As such, I probably do not belong in this society. I've had a long interest in neutron stars. This interest began ...
-1
votes
1answer
83 views

What would happen if neutron beam hits a neutron star? [closed]

Suppose there is a continuous stream of neutrons constantly hitting a neutron star, does it adds to the mass but do the surface of the neutron star still remains fairly even? How about nuclear fusion ...
-1
votes
1answer
79 views

If light was 2 parts per trillion slower than gravitational waves, would we know this from Gauss' law? [duplicate]

In the recent neutron star merger. The gravitational waves started 100 seconds before the collision, which is when they reached a max and STOPPED. The mass quadrupole had stopped changing, which means ...
2
votes
2answers
128 views

Effects of a neutron star merger

After the announcement of a neutron star merger on 16 October, I have been wondering how close such a merger would have to be in order to generate effects that could affect life on Earth. For example,...
3
votes
0answers
76 views

Neutron star merger: large scale dynamics

Yesterday was announced the first detection of a neutron star merger via gravitational and electromagnetic waves. On the announcement one of the speakers is showing a simulation of the dynamics of ...
31
votes
2answers
3k views

Why did the neutron star merger signal last for so much longer than the black hole merger signals?

Just recently, LIGO and Virgo successfully detected new signs of gravitational waves. This time, instead of colliding black holes, it is a pair of colliding neutron stars. This collision emits light ...
58
votes
4answers
8k views

Why did the gamma ray burst from GW170817 lag two seconds behind the gravitational wave?

The ABC, reporting on the announcement of gravitational wave GW170817, explained that for the first time we could identify the precise source of a gravitational wave because we also observed the event ...
1
vote
0answers
175 views

What does the “black body” spectrum look like from a neutrom star?

In a recent discussion I learned that when neutron stars form they cool down much quicker than a black body of the same size and temperature because they can radiate neutrinos from their interior as ...
16
votes
1answer
2k views

Why can a neutron star implode? [duplicate]

In a book* I was reading, it said that a neutron star is formed when the pressure is so large that the electrons in a white dwarf interact with the protons, forming neutrons. The neutrons then ...
0
votes
1answer
357 views

Difference between neutron degeneracy pressure and thermal pressure of a neutron star

I'm solving TOV (Tolman-Oppenheimer-Volkoff) equations and i'm just confused in first equation of TOV equations. The pressure involved in TOV equations is a thermal pressure or neutron degeneracy ...
3
votes
2answers
237 views

Magnetic decay versus rotation braking of neutron stars

A canonical pulsar can be described as a ball of mass $M \approx 1,44 \, M_{\odot}$ and radius $R \approx 10 \, \mathrm{km}$, rotating with a period of about $P \approx 5 \, \mathrm{ms}$. It also ...
4
votes
1answer
68 views

How to justify the maximal value of a star's magnetic field at surface?

In many lectures, it is stated that the maximal value $B_{\text{max}}$ of the magnetic field at the surface of a star can be found in Newton's gravitation theory by equating the gravitational ...
6
votes
1answer
389 views

Neutron stars - only neutrons?

I was at a museum recently, and there was a display on neutron stars. It said that neutron stars are made only of neutrons, which honestly didn't make much sense to me - neutrons decay very quickly on ...
3
votes
1answer
115 views

Where does the 10 km of neutrons stars comes from? [duplicate]

Neutrons stars are known to have a radius of about 10 km to 15 km. Where that size comes from ? How to theoretically derive that number, using Newton's theory of gravity ? I know the magnetic flux ...
-1
votes
1answer
125 views

what is meant by Newtonian Polytrope?

I study about newtonian polytrope n = 1 that for this polytrope steller radius does not depend on mass and central density. I want to know are there some more polytropes that are known as newtonian ...
1
vote
1answer
74 views

Do neutron stars have enough magnetic pull to move or effect other stars? [closed]

Do neutron stars have enough magnetic energy to pull our Sun?
23
votes
4answers
559 views

Due to relativity, does the surface of a pulsar have less area than the layer beneath it?

A pulsar or spinning neutron star can reach relativistic angular velocities. Special relativity asserts that objects traveling near the speed of light contract in length. Therefore, it seems ...
6
votes
1answer
126 views

How does fermion degeneracy affect elastic scattering in astrophysical compact objects?

As I currently understand it, absorption processes or inelastic scattering involving fermions in a degenerate gas are strongly inhibited, because to change the fermion energy (or create a new fermion) ...
6
votes
1answer
209 views

Why is the speed of sound a quantity of interest in nuclear astrophysics?

According to E. Chabanat et al. (1997), the speed of sound in a nuclear medium is defined as $$\left(\frac{v_s}{c}\right)^2 = \frac{dP}{de}$$ with $$P = \rho^2 \frac{dE/A}{d\rho}$$ and $$e = \rho\...
1
vote
1answer
250 views

Why don't neutron stars transform into proton stars as a result of neutron beta decay? [duplicate]

Free neutrons, as we know them, are unstable and hence undergo a three-body decay into proton, electron and antineutrino with a mean lifetime of just under 15 minutes. But there are astrophysical ...
1
vote
1answer
110 views

Circular orbits and neutron stars

For a black hole with Schwarzschild radius $r$ it is true that there are no circular orbits around the centre of this black hole with radius smaller than $\frac{3}{2} r$. Is it possible to have ...
2
votes
1answer
94 views

What is meant by effective nuclear interactions?

I am new to astrophysics... I am confused by the term effective nuclear interaction SLy of the Skryme type. Would anyone define me briefly that phrase and some reference related to it?
34
votes
2answers
2k views

Can a neutron star become a black hole via cooling?

How much does thermal expansion affect neutron stars? Would the loss of temperature cause a neutron star to be more densely packed and thus collapse into a black hole?
1
vote
1answer
36 views

Accretion neutron star; mass gain 0.8m?

My textbook on Astrophysics says the following about accretion (translation): Assume we have a particle with mass $m$ that falls on a neutron star; $R\approx 10$ km, $M\approx 1.4M_{\text{sun}}$, ...
0
votes
2answers
116 views

Possible for certain black holes to transform into neutron stars?

Considering that space-time is expanding at an increasing rate or perhaps during times of inflation - could a black hole just above the neutron star threshold experience a decrease in density to ...
-1
votes
2answers
557 views

Are all 'substances' made of atoms?

Is there any other large collection of particles other than atoms that would fit our traditional intuitive definition of a substance? Something that would appear similar to a solid liquid or gas. ...
3
votes
4answers
221 views

Can stars contain neutron-star dense cores?

purely for curiosity: are there any conditions under which a small amount of neutron star matter (400 trillion grams per cubic centimeter) could be at the core of a star or planet? neutron star ...
0
votes
1answer
651 views

Gravitational time dilation and neutron stars [closed]

How great is the gravitational time dilation close to a neutron star? How would the effects of gravitational time dilation compare with the event horizon of a black hole?
1
vote
2answers
440 views

What if I shot protons and electrons at a neutron star

Could I create a massive element simply by putting protons into a neutron star? And then forcing electrons to orbit it?
2
votes
1answer
83 views

Is it possible that matter mass of a star more than total gravitational mass?

Matter mass of a star can be found from $$M_\rho =\frac{1}{2} \int \rho r^2 dr .$$ On the other hand, there is also gravitational mass of a star in the Schwarzchild metric $$ 1- \frac{2M}{r}.$$ ...
1
vote
0answers
42 views

More conditions needed for determining the moment of inertia

I am solving the moment of inertia for a neutron star using equations: $$\frac{dI}{dr}=\frac{8\pi}{3}\frac{(\epsilon + P)f(r)j(r)r^4}{(1 − 2M/r)}\tag 1$$ $$\frac{d}{dr}\bigg(r^4j(r)\frac{df}{dr}\...
1
vote
1answer
100 views

Can be possible that a neutron star has a negative gravitational surface redshift?

I am looking for some strange stars that is gravitationally blue shifted. A star surface redshift determines mass-radius relation for chargeless star. Can be possible that a charged neutron star ...
2
votes
1answer
1k views

What are saturation density and nuclear drip point?

What is meant by nuclear saturation density and neutron-drip point? How can we relate the both densities? Where do these densities occur in the layers of neutron star and by what reactions a star ...
0
votes
2answers
557 views

Is total energy density in energy-momentum tensor equal to total energy density with relativistic mass density?

I am studying the Tolman-Oppenheimer-Volkhoff (TOV) equations of hydrostatic equilibirium: $$\frac{dP}{dr}= −(G/c^2)(\epsilon + P)\frac{M + \frac{4\pi(r^3)P}{c^2}}{r^2− \frac{2GMr}{c^2}} \tag{1}$$...
-1
votes
1answer
213 views

In TOV equations of hydrostatic equilibrium

in TOV equations of hydrostatic equilibrium $\{P(r),M(r),v(r)\}$ are coupled with 1st order and $P(r)$ , $M(r)$ have initial values at $r=0$ but $v(r)$ is at the boundary of the star. Therefore, when ...