Questions tagged [neutron-stars]

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Why do Type II supernova happen? [duplicate]

I am an engineer and not a physicist. I am unable to understand why SuperNova happen. I understand that when the core is composed of high atomic number of elements like Iron and further fusion is not ...
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Are neutron star cores thought to be stiffer than photon gases?

The weak energy condition and with the dominant energy condition allow anything from w=-1 to 1 (meaning that the magnitude of the pressure can be at most equal to the total mass-energy density). ...
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2answers
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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 ...
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1answer
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Artificial degenerate matter (by “non-explodey” methods) — physically plausible?

White dwarf matter, neutron-degenerate matter (I'm still confused as to whether this is the same thing as "neutronium" or not), and other possible types of degenerate matter like quark stars are ...
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4answers
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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 ...
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1answer
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How do neutron star binaries form?

Do neutron star binary systems come from previously active-star binaries, where where both stars have gone supernova and left behind neutron stars that are still in orbit? Or do they form when two ...
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What's the shortest “safe” distance from a neutron star merger?

Take GW170817 for example, the first neutron star collision picked up by LIGO. Given how much data we got from that event, can anyone figure out what the "blast radius" is, and how far away from the ...
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Can Thorne–Żytkow object (heavenly body) exist in universe?

Can Thorne–Żytkow object (heavenly body) exist in universe? It's a new concept I came across. Are there such heavenly bodies in universe? It's a heavenly body in which a neutron star is present inside ...
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Neutron star modelling with polytrope

I want to model the density profile of a neutron star with 1.4 $M_\odot$ with a polytrope $p=\kappa\rho^{\gamma}$ with $\gamma=1+\frac{1}{n}$. I started with $n=\frac{1}{2}$ and solved the Lane-Emden ...
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1answer
167 views

Qualitative picture or reference for a Lemaître's Cold Big Bang theory

Warning: please, consider this question to be motivated by historical curiosity or as an exercise in model-building. I believe this cannot be considered non-mainstream physics as it was very much ...
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1answer
243 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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4answers
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Why were pulsars not discovered in the visual spectrum?

In 1967, the first pulsar was discovered at a radio observatory in Cambridge. Radio astronomy started around the 1930s, but astronomy in the visible part of the spectrum had been done for a long time ...
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Percentage of Neutron Stars that leave the Galaxy

When a neutron star(NS) is born the supernova kick gives the newborn NS a certain boost in a supposed isotropic direction and, depending on how strong the boost is and on the position of the NS at ...
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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. ...
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Gravitational $N$-body mergers?

Beyond binary systems and its mergers, have numerical relativity groups computed an approximation to $N$-body GW signals/waveforms or is that a hard unsolved task?
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Where do gravitational waves draw the energy from?

Imagine binary neutron stars inspiral, they generate gravitational wave which carries energy away and causing the pair to become ever closer. Since all wave must carry energy I wonder where do ...
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How do LIGO and Virgo know that a gravitational wave has its origin in a neutron star or a black hole?

It is being said that gravitational-wave detectors are now able to distinguish neutron star waves from those originating from black holes. Two Questions: How do LIGO and Virgo know that a ...
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4answers
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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 ...
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How does a Thorne Zytkow star die?

A Thorne-Zytkow star is one where a red giant or supergiant contains a neutron star at its core, formed from the collision of the giant with the neutron star. It is believed that one has been found in ...
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Doubt about the Einstein Field Equations (EFE) of a Magnetar

The Schwarzschild solution could be an good model for a planet and a star, without rotation and electric and magnetic charge. Besides the fact that this solution is spherically symmetric. The metric ...
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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 "...
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Strange quarks in neutron stars

Recently I have read that the pressure within neutron stars can be so extreme that it can cause the deconfinement of quarks to form a kind of quark 'soup' and that these extreme conditions allow for ...
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What is inside a black hole? [duplicate]

I'm trying to understand what causes a black hole in terms of it's composition. We know a start can die and collapse into a neutron star, but if the neutro star is not dense enough to create a black ...
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Do different neutron stars have different density?

When stars go supernova, a neutron star may be left over if there isn't enough mass to create a black hole. Based on the mass present, will a neutron star have a varying density or is the radius ...
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Is there a relatively painless way to calculate the radius of a neutron star, given its mass?

I know there are different models based on, as I understand it, different equations of state describing the neutron star mass-raduis relation. I'm not sure what to do with that, though. My math isn't ...
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Is getting nudged from a neutron star to a black hole catastrophic?

A recently released SF book has single neutron star on the veritable edge of collapsing into a black hole... "What's going on with the star?" "It's massive. I mean, like, spit-on-it-and-it'll-...
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1answer
244 views

The inside of of a black hole

I am looking for a confirmation (or correction) of my thinking about the nature of the black holes. As I am not a physicist and only a physics enthusiast, my understanding is probably very simplified ...
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How does gravity affect sound waves? [closed]

Someone asked me this question and I don't think I gave him an adequate answer (I was trying to think of the extreme case - that of neutron stars)
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584 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?
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1answer
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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 ...
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10answers
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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 ...
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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 ...
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2answers
70 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 ...
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1answer
101 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$^-$ $\rightarrow$...
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2answers
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Can a stellar black hole revert into neutron star or whatever it was?

When a massive star cannot produce sufficient energy to counter it's weight the result is often a neutron star which is stabilized by quantum mechanical effects, say given enough mass to overcome such ...
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1answer
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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 ...
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1answer
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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 ...
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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 ...
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1answer
38 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} = \...
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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)...
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1answer
646 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 ...
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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 ...
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What happens to Protons and Electrons when a Neutron star forms?

What happens to Protons and Electrons when a Neutron star forms? At some point gravity overcomes the Pauli Exclusion Principle ( I assume) and they are all forced together. What happens in the process?...
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1answer
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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 ...
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1answer
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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 ...
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2answers
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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?
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1answer
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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?
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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?
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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 ...
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2answers
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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 ...