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Questions tagged [neutron-stars]

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8
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2answers
535 views

Gravitational waves and chirp waveform

When two neutron stars collide emitting gravitational waves, what exactly does the chirp waveform represent and how is it used to infer the distance to the source?
3
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3answers
110 views

Why do neutron stars with more mass have smaller volume?

I know about Heisenberg uncertainty which makes more localized neutrons have a wider range of undefined momentum, and Pauli exclusion principle which prohibit neutrons from getting too close or "...
1
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1answer
105 views

What is the closest distance for an undiscovered old neutron star and how long would it take to get here? To help people scared of neutron stars

This is to help people who are scared of neutron stars. My questions are What is the faintest a neutron star could be How close could it be and not yet be detected How long would it take to get here ...
0
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0answers
43 views

How to calculate the corotation radius?

I am studying this paper: P.Ghosh & F.K.Lamb, APJ, 232, pag.259 (1979) I do not understand how the authors calculate the corotation radius, $r_{co}$, where the matter of the disk has the same ...
0
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2answers
53 views

Can an invisible neutron star exist? [duplicate]

Basically a neutron/quark star that approaches it's Schwarzschild radius but doesn't surpass it. Its gravitational force is great enough to not let light escape from it, but not great enough to become ...
1
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1answer
46 views

Forming a Neutron Star: inverse $\beta^-$ decay or electron capture?

There are three different kinds of beta decays: $\beta^-$: n $\rightarrow$ p + e$^-$ + $\overline{\nu}_{e^-}$ $\beta^+$: p $\rightarrow$ n + e$^+$ + $\nu_{e}$ electron capture: p + e$^-$ $\rightarrow$...
2
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1answer
28 views

Running coupling constants within a highly compressed object

I wonder is it possible. in highly compressed objects, such as neutron stars and black holes, (I'm not sure that this applies to singularities), that the physical conditions within these objects ...
3
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1answer
59 views

BCS theory for neutral fermions

As I understand it, Cooper pairs form between two fermions and are the cause of superconductivity. I was told by a teacher that the formation of Cooper pairs and BCS theory requires both fermions to ...
0
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0answers
32 views

Magnetar's magnetic field near a black hole (novice question)

Even light cannot escape the event horizon of a black hole. Now, imagine a magnetar orbits a black hole. The magnetar orbits too far to be ripped and consumed by the black-hole. However, its magnetic ...
1
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1answer
71 views

How common are neutron stars?

I thought this would be a rather easy question to answer, but it doesn't seem to be addressed anywhere. I haven't even been able to find a paper, article, or page that says it's unknown how common ...
1
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1answer
33 views

Neutron Star LMXB Accretion Spin-Up Estimation

I've been asked to estimate how much mass a neutron star in a low mass X-ray binary would have to accrete in order to be spun up to ~300 Hz. I found the conservation formula $\frac{d(I\omega)}{dt} = \...
1
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0answers
32 views

Examples of perturbative force-free electrodynamics on top of vacuum solutions?

Imagine I have a solution $A_{(0)\mu }$ for the four-vector potential of vacuum electrodynamics. That is, the solution fulfills source-free Maxwell equations $F^{\mu\nu}_{(0)\;\;;\nu} = 0$ with $F_{(0)...
1
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1answer
75 views

Is it possible to test the physical reality of extra dimensions predicted by string theory?

I have no business asking this question since I am not a string scientist but I like to follow science news in phys.org and I read an article dated today Gravitational waves provide dose of reality ...
0
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1answer
50 views

Neutron degeneracy pressure and the Schwarzschild radius

Does the Schwarzschild radius exist at the exact tipping point where neutron degeneracy pressure fails? For example, consider a hypothetical neutron star that is being held up just below the limit of ...
2
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2answers
83 views

What is the energy required to create a gravitational field equivalent to that a mass $m$ shows?

If the mass of a neutron star in its collapse becomes a singularity, then the resting energy of this gravitational field must be $E = mc^2$ ($m$ = star mass). Is this possibility wrong?
0
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1answer
382 views

What will happen if a magnetar gets close to Earth?

I have studied that magnetars are a type of neutron stars which are the most powerful magnets in the Universe. Their field strength can be of $10^{13}$ Tesla or even more. What effect would one have ...
1
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3answers
109 views

Does the neutron star collapse from the surface to the center or from the center to the surface?

I think the collapse begins at the surface because in this place the gravity is always more intense than in the center. That's right?
0
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0answers
73 views

How does a neutron star collapse into a black hole?

Neither this answer nor this answer answers my question. I want to know more details of how a neutron star collapses into a black hole. One possible way it does so is once a neutron start is massive ...
0
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1answer
29 views

Phase transition and energy conservation inside neutron star

I'm stuck at the moment with this simple question: If a phase transition from hadronic to quark matter of 1st order with a big jump in the energy density occurs inside a neutron star one can get ...
2
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2answers
121 views

Can gravitational waves be emitted from single neutron stars?

I wonder whether GWs can be produced and emitted by single neutron stars, since it is known that typically they must be emitted by a binary system of them. If so, can the source be an isolated cool ...
2
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0answers
28 views

How can a neutron star have a magnetic field when its particles are neutral? [duplicate]

I understand that it is a celestial object of very small radius (typically 18 miles/30 km) and very high density, composed predominantly of closely packed neutrons. Neutron stars are thought to form ...
1
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2answers
210 views

How can a neutron star radiate when it is neutral? [duplicate]

We know how to define the Temperature of a neutron star, as answered in this question. After watching the Sixty Symbols video about Forging Weapons from Neutron Stars, where the temperature and ...
2
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1answer
94 views

What happens when a neutron star loses enough mass to go under Chandrasekhar limit?

Say if a blackhole passes very close by a neutron star at high speed fly-by and eats half of the neutron star. What happens to the other half? Does it blow up in size as the electroweak force pushes ...
1
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2answers
216 views

In-between neutron stars and black holes

Current knowledge and theories,...Suggest a maximum mass for neutron stars about 2-3 solar masses, and is generally assumed that black holes are ANY compact object above that or more generally 5 solar ...
2
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0answers
50 views

On the conversion of neutron stars in deconfined quark stars

Imagine a neutron star, constituted of nucleons ($p$, $n$) and charged leptons (say $e$ and $\mu$), can decay into a deconfined quark star through some process. Given the Bodmer-Witten hypothesis, the ...
2
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1answer
173 views

Free fall time of collapsing non-rotating star in GR according to a distant observer

Suppose a star with a spherically symmetric mass distribution, mass $2\cdot M_{sun}$ and initial radius $R$, undergoes a gravitational collapse after all gas pressure has vanished. The final radius ...
8
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0answers
173 views

What is the Chandrasekhar-Friedman-Schutz (CFS) instability, exactly?

I am confused as to what the Chandrasekhar-Friedman-Schutz (CFS) instability is, exactly. It seems to partially refer to this paper (https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.24.611) ...
4
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1answer
77 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
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2answers
154 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 ...
0
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5answers
101 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
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1answer
38 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
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1answer
73 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
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1answer
62 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
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2answers
208 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 ...
0
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0answers
45 views

What will happen when neutron star-material touches regular matter?

I do know matter will become the same material as neutron star if it landed on neutron star because of the strong gravitational effect. But what's going to happen if a very small amount of pure ...
2
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3answers
239 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
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1answer
31 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
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1answer
248 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
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0answers
52 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
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1answer
223 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 ...
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0answers
56 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 ...
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2answers
61 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
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0answers
18 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
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2answers
177 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
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1answer
66 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
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1answer
76 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
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2answers
124 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
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0answers
75 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 ...
30
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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 ...
57
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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 ...