Questions tagged [neutron-star]

Questions regarding a degenerate star that is mainly composed of neutrons.

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How do neutron stars maintain inhomogeneous surfaces and migrating "hot spots"? (e.g. SGR 1830-0645)

News item NASA's NICER Tracks a Magnetar's Hot Spots and Phys.org's Properties of magnetar SGR 1830−0645 inspected with NICER reference the January 14 2022 arXiv Pulse Peak Migration during the ...
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6 votes
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Do “neutrino supernovae” exist?

Core collapse supernovae release most of their energy in the form of neutrinos. About 1% of the neutrinos are absorbed by the thick outer envelope which powers a spectacular supernova explosion. Core ...
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Is it coincidence that the change in GPE when falling from deep space into the largest know neutron star is approximately mc squared Joules?

We can calculate the change in GPE in falling from a very long distance to the surface of a star or planet from $$\Delta{GPE} = \int_{r}^{\infty}mg\,dh $$ But taking into account that g will change ...
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5 votes
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What is the spectral reflection curve of cold white dwarfs and neutron stars?

Suppose that I got a white dwarf and a neutron star and after some trillions of years their temperature are down to just a few °K so cold that they don't emit any appreciable black body radiation. Now,...
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5 votes
1 answer
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Difference between NSBH and BHNS mergers

What's the difference between Neutron Star-Black Hole Merger (NSBH) and Black Hole-Neutron Star Merger (BHNS)? Are they the same names for the same events or is there any difference between them? I ...
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0 votes
1 answer
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Is a black hole really a neutron star with a gravitational time dilation factor of 1.0

Here's why I'm asking. The gravitational time dilation factor at the surface of a star or planet can be expressed as $$gr/c^2$$ In theory, the same equation should apply to the gravitational length ...
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9 votes
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Metallicity in gravitational wave astronomy

Metallicity relates to the quantity of elements in an object that are heavier than hydrogen and helium. I often see this terminology in recent studies of gravitational waves such as this paper. If I ...
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8 votes
1 answer
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Rotation direction of Pulsars

Pulsars are rotating neutron stars observed to have pulses of radiation at very regular intervals that typically range from milliseconds to seconds. It has a very strong magnetic fields which funnel ...
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3 votes
1 answer
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What is this strange animation of a pulsar likely trying to illustrate? One beam is normal, the opposite gets wrapped like coiled rope?

The November 2020 Sixty Symbols video How Smooth is a Neutron Star? (linked below) describes negative LIGO results looking for weak but very periodic signals from rotating neutron stars that might ...
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13 votes
2 answers
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Have we observed any static neutron stars? [duplicate]

Neutron stars are one type of remnant of a giant star's core after its collapse. Neutron stars tend to rotate at very high speed and the mismatch between its axis of rotation and magnetic pole make it ...
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5 votes
3 answers
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What does it mean for a proto-neutron star to be opaque to neutrinos?

I have read that a proto-neutron star is opaque to neutrinos but I do not really know what does means. Could someone explain this to me? I am a mathematician, not a physicist so I found it hard to ...
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1 answer
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What is the relation between size (radius) of an astronomical object and the speed of oscillation of 'light' coming from it? (Strength/amplitude)?

From the year-end issue of New Scientist Magazine (Dec. 18-31,2021): Astronomy: 'Space Cow' explosion was probably a failed supernova' Page 10: 'They found that the strength of this radiation ...
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How would a cooled down neutron star look like when illuminated?

Assume we have a neutron start hat has cooled down so far that it no longer emits visible light. If we illuminate it with a powerful external light source, how would it look like? Would it reflect ...
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10 votes
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How big would a telescope have to be to get a good look at the nearest neutron star?

It's my understanding of observational astronomy that the size of a telescope limits its effective angular resolution, which is why scientists needed to use radio telescopes all over the globe to look ...
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5 votes
1 answer
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What is the smallest neutron star radius possible?

According to the Chandrashekhar limit the minimum mass of a neutron star is about 1.44 solar masses, however I found some examples of neutron stars less massive than that. Additionally, I thought that ...
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7 votes
2 answers
181 views

Why is the number density of neutrons much larger in neutron stars?

There is a particular argument given in Concepts In Thermal Physics by Blundell that I'm not able to understand: A free neutron can decay with a mean life of about $15$ minutes but in stars, we have ...
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3 votes
0 answers
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What's the mass distribution of elements created in neutron star mergers?

In charts like this, you'll see that a bunch of the heaviest elements mostly come from neutron star mergers. But what about the mass distribution of just the products of neutron star mergers? That is, ...
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4 votes
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Is there a mass-vs-radius chart for neutron stars?

I'm aware that we currently don't have an equation of state for the radius of a neutron star, because we don't know what happens to neutrons at their cores, and because the equations involved with ...
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2 votes
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In what year (2014?) the gravitational wave triggered by this merger was possibly generated?

Re: "A transient radio source consistent with a merger-triggered core collapse supernova" https://www.science.org/doi/10.1126/science.abg6037 Actually the described merger consisted of two ...
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11 votes
1 answer
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Does the average proton/electron density in a neutron star change with mass?

My understanding is that although electron degeneracy prevents beta decay, there are still a few protons and electrons hanging around. I also understand that, at least in white dwarfs, as the mass ...
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6 votes
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Is "magnetars don't last long — just a year to a few years" really true? Is it a misquote or perhaps taken out of context?

NASA's Two Sides of the Same Star discusses the relationship between pulsars and magnetars and contains a video also linked below. At 02:13 it quotes "Tom ...
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1 vote
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What does an electron-capture supernova leave behind? A white dwarf, a neutron star or nothing?

Somehow, none of the many articles I've read about the recent discovery of electron-capture supernovae has specifically said what they leave behind as remnants.....
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4 votes
1 answer
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Are there black holes and neutron stars in satellite dwarf galaxies orbiting around Milky Way?

It is thought that the number of satellite dwarf galaxies orbiting around Milky Way is counted in hundreds. Are there black holes and neutron stars in satellite dwarf galaxies orbiting around Milky ...
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3 votes
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Can we use asteroseismology to study neutron stars?

Asteroseismology study the propagation of sound waves inside a star to probe its internal structure. Could something similar be used to study the structure of neutron stars and put constraints on the ...
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-2 votes
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Could observation of GL or other image phenomena from system of 2 merging massive dense objects and of GW caused by their merge be connected?

What is the probability to observe gravitational lensing (or any other image related phenomena) from the pair of black holes (or pair of neutron stars or black hole - neutron star) which are about to ...
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6 votes
2 answers
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Can dark matter be normal matter after all? [duplicate]

MACHO's and RAMBO's are both baryonic (and leptonic) forms of matter that can't be observed by their nature. They barely emit or reflect light. Black holes, neutron stars, or brown dwarfs (or groups ...
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1 vote
1 answer
131 views

Is the smaller companion of Pulsar J0453+1559 still the smallest known neutron star? Was it further confirmed to be a NS after Martinez et al. (2015)?

@ProfRob's Physics SE answer to What is the theoretical lower mass limit for a gravitationally stable neutron star? was linked just now in their answer to Can a neutron star ever be less than about 1....
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4 votes
3 answers
184 views

What escape velocity would quark stars have?

Quark stars are hypothetical compact stars that are denser than neutron stars and maybe the last stage of upholding matter before stars that collapse into a singularity. Neutron stars have escape ...
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3 votes
1 answer
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Can a neutron star ever be less than about 1.44 solar masses (the Chandrasekhar limit)? Why not?

I learned about the Chandrasekhar limit as being the UPPER limit, in terms of mass, for a white dwarf... But, I have never heard of a neutron star being BELOW that mass, so I have wondered, recently, ...
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15 votes
3 answers
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Is there anything different about the gravitation around a non-spinning black hole and a neutron star of the same mass?

If we perform a simple experiment by orbiting identical spacecraft around a non-rotating black hole and a non-rotating neutron star of equal mass at a "safe" distance, and ignore differences ...
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0 votes
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Is something wrong with my luminosity calculation?

A few million years after a white dwarf forms, its surface temperature reaches $100000\text{K}$, while its radius is $0.01R_\odot$. Would this mean that its luminosity is $\Big(\dfrac{100000}{5778}\...
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1 vote
0 answers
71 views

Strange matter objects other than neutron stars?

This question is about celestrial objects which are composed by exotic matter, and exotic matter I define as states of matter that are not commonly encountered such as Bose–Einstein condensates, ...
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3 votes
1 answer
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Are there any known neutron star - supergiant binaries?

After looking for more information about TZOs (Thorne-Zytkow Object), I came up with a question that I had trouble finding answers on the Internet. Do we know of any future TZOs, supergiants being ...
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2 votes
0 answers
79 views

Can a Thorne-Żytkow object be the progenitor of a modern quasi-star?

I was reading some Wikipedia articles about astronomy, and came across an interesting line: The neutron star may also accrete sufficient material to collapse into a black hole. Now, here is my ...
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3 votes
0 answers
46 views

Can mass loss via accretion occur on stellar remnants?

We know that normal stars can lose mass to a binary companion. But can this happen to neutron stars and white dwarfs? Let's say a stellar black hole is being orbited by a white dwarf or neutron star. ...
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2 votes
0 answers
68 views

What would happen if a neutron star merged with a white dwarf?

We've heard of neutron star mergers and white dwarf mergers. But what would result in a neutron star merging with a white dwarf? Would there be a similar super/kilonova, are there any examples of it, ...
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4 votes
1 answer
100 views

Can a star be massive enough to go 'supernova' yet not be massive enough to leave behind a neutron star? Or, perhaps vice versa?

From what I understand, stars that explode as a supernova at the end of their lives become either a black hole or a neutron star, and less massive stars that do not explode become white dwarves, but......
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2 votes
1 answer
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The star that died and became the Crab Nebula and Crab Pulsar?

The supernova of this star was witnessed about 1 thousand years ago, and the star's remains are the Crab Nebula and Crab Pulsar. What is this no longer existent star called? How massive was this star? ...
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5 votes
1 answer
388 views

Stellar life cycle flow chart with mass conditions and time scales

I remember that in my nuclear astrophysics lecture a decade ago, our lecturer drew a large flow chart like diagram of stellar evolution in dependence of the mass of the star (in solar units) on the ...
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1 vote
1 answer
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What about the magnetic field strength inside of an old accreting neutron star?

As the magnetic field strength outside an old accreting neutron star is thought to be small (about $10^8-10^{10}$ Gauss), what about it inside the star? Because of the superconductivity and ...
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2 votes
0 answers
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What is the gravitational wave spectrum of an ellipsoid neutron star like?

If the star is ellipsoid instead a sphere, the wave should be rich of harmonics, not only (2*orbital frequency). Can these harmonics behave the same way, i.e. they appear/disappear together and drift (...
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1 vote
1 answer
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How big would the supernova when a neutron star collides with another neutron star? [closed]

If two neutrons stars that are orbiting were to collide, how big would the supernova explosion be? Would a new black hole or a new supernova remnant be formed?
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1 vote
1 answer
74 views

Question about redshift and effective gravity at the rotating neutron star surface

For a rapidly rotating neutron star, if consider the star as a sphere, redshift at the equator surface will be larger than at the pole. But if consider the star as an obsolate sphereiod (the ellipsoid ...
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3 votes
1 answer
179 views

Do neutron stars have an ergosphere?

Ergospheres are a property of black holes, and do neutron stars have it? If yes, why seldom article mentions that; if no, why can't neutron stars have this ergosphere component?
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3 votes
0 answers
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How could we search for old cold neutron stars?

This is the inverse of Will Gaia detect inactive neutron stars? (to which the answer was "probably not"). So if Gaia can't do it, what would it take? How could such a search work, and what ...
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3 votes
1 answer
305 views

Assuming proton decay is false, what's the ultimate fate of a neutron star or white dwarf?

A still unproven theory that protons can decay, and have a halflife of $10^{30}$ years or so, meaning eventually all matter will dissolve because their constituent protons and therefore neutrons will ...
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5 votes
1 answer
778 views

Is nuclear pasta or neutron star crust iron stable outside of neutron stars?

When neutron stars collide, they crash into and kill each other in a kilonova explosion, which blasts a lot of their material into space. A huge amount of neutronium, neutron star stuff, is suddenly ...
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3 votes
2 answers
525 views

Is there a Vela Nebula?

The Vela pulsar is a neutron star from a supernova that exploded 10,000 years ago. It spins 11 times a second. The Crab Nebula along with the central Crab Pulsar formed 1000 years ago. This pulsar ...
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2 votes
1 answer
78 views

How did Fermi manage to see neutron star merger?

When the GW170817 neutron stars merger was observed by LIGO/Virgo, the Fermi gamma-ray telescope observed the event 2s after the merge. How did it know where and when to look? It must take some time ...
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3 votes
1 answer
107 views

Why do objects appear blue while on a neutron star?

I was playing around in Space Engine recently, and I realized I hadn't yet landed on a neutron star. This seemed like a very sensible thing to do, so I did it and chose a (relatively) well-known one ...
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