Questions tagged [neutron-star]

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

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Can Neutron Star merger remnants solve the black hole mass gap? Why can't we observe them?

The mass of neutron stars is generally agreed to be anywhere between the Chandrasekhar limit of $1.39M☉$ and the Tolman–Oppenheimer–Volkoff limit, which ranges from $2–2.16M☉$. Anything above is ...
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According to this article the max mass of a non-spinning neutron star is around 2.5 solar masses. What is defined as a non-rotating neutron star?

This is the article as mentioned above: The Maximum Mass of a Neutron Star is 2.25 Solar Masses To repeat, according to this article, the maximum mass of a non-rotating neutron star is around 2.5-3 ...
Stefan 's user avatar
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Why do double neutron stars remain bounded?

I read that in principle, the formation of a double neutron star requires that at the time of the second supernova explosion the binary consists of a $\sim$ 1.4 solar mass neutron star, and a second ...
some_math_guy's user avatar
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About angular diameter, parallax and image of the nearest neutron star RX J185635-3754

I have a big doubt about our allegedly nearest (X Ray isolated) neutron star, also known as the Walter star, one of the members of the "Magnificent Seven stars": RX J185635-3754. So I came ...
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What are the most up to date, accepted, evolution stages of big stars that end in compact objects or a planetary nebula?

There are numerous charts and diagrams showing the stages of stellar evolution, as: or among many more (you can find several after googling a little), for example. When I studied my B.Sc. on Physics,...
omivela17's user avatar
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Lifespan of neutron stars and black dwarfs in terms of mass in years

Stars have a lifespan scaling as $1/M^{2.5}_\star$ for sunlike stars or more generally $t\sim 1/M^3$ for general stars (more or less), black holes have a lifespan (according to simple Hawking ...
riemannium's user avatar
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Number of neutron stars by radiation band

Since the number of known neutron stars ain't reached yet 4000 at the time of writing, I am wondering about how neutron stars are classified in terms of their radiation spectrum. Clearly, some neutron ...
Jimmy Bionic's user avatar
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How long would we survive an approaching neutron star?

I recently came across PSR B1620−26. A neutron star that captured a sun like star with an orbiting planet. The system went through several stages of development, but through it all the orbiting planet ...
Bradtvford's user avatar
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1 answer
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Why is nuclear pasta the strongest part of a neutron star?

From my very rudimentary understanding of neutron stars taken from the abstract to "Elasticity of Nuclear Pasta", nuclear pasta is the strongest substance, hence the strongest part of a ...
Ben A.'s user avatar
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What would the collapse of a white dwarf to a neutron star look it

It’s hypothesised that some white dwarves, when raised in mass above the Chandrasekhar limit, will instead of producing a type 1A supernova, will instead collapse into a Neutron star. What would this ...
blademan9999's user avatar
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Degenerate object accretion - what happens after it becomes a PMO?

Degenerate objects such as neutron stars and white dwarfs can be accreted from by other objects. As the degenerate object loses mass, it could pass through different mass ranges which govern the ...
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Meaning of Bidirectional Arrow in a Fitting Formula

I was reading this paper on the ejecta mass of compact binary mergers and came across this notation in equation (6): $$\frac{M_\text{dyn}}{10^{-3}M_\odot}=\left(\frac{a}{C_1}+b\frac{M_2^n}{M_1^n}+cC_1\...
hikari30's user avatar
2 votes
1 answer
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What is the maximum radius of a pure iron-56 planet?

Suppose we are building a pure iron-56 planet atom by atom, how large can it get in terms of radius before it collapses into a black hole?
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There is a decibel limit to sound based on the medium, what is the decibel limit in neutronium?

I've been participating in many discussions online about the classic thought experiment on pressing a button a light year away with a light year long rod. The solution boils down to the speed of ...
Aaron Hathaway's user avatar
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1 answer
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Do collisions of stars still undergoing fusion reactions produce gravitational waves?

When studying gravitational wave sources, we just consider BNS, NSBH, and BBH systems since their inspiraling and collisions can produce detectable graviational waves. Also according to the paper &...
noob anomaly's user avatar
9 votes
2 answers
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Lightest Neutron Star ever observed?

Fundamentally, my question is, is this a real and confirmed observation? Or is there a too-high margin of error for now? Inspirational discoveries, Lightest neutron star ever discovered might ...
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Why does electron degeneracy pressure not stop massive star collapse?

I was thinking a little bit, and never asked myself the following. If white dwarfs do not collapse, because electron degeneracy pressure stops the star from collapsing by its own gravity, and this is ...
martín canullán's user avatar
4 votes
1 answer
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"Holy grail" future observation to confirm presence of neutron stars in the centers of massive, otherwise conventional stars? (Thorne–Żytkow objects)

Wikipedia's Thorne–Żytkow object begins: A Thorne–Żytkow object (TŻO or TZO), also known as a hybrid star, is a conjectured type of star wherein a red giant or red supergiant contains a neutron star ...
uhoh's user avatar
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Could a quasi-neutron-star exist between the maximum mass of a star and the mass of a quasi-star?

A quasi-star is a hypothetical supermassive star that is so heavy its core collapses into a black hole as it is still forming. The matter accreting into the black hole then generates radiation ...
Hene's user avatar
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How much would you weigh at the equator of the fastest spinning pulsar?

Assuming you have a mass of 70 kg, what would your weight be on the equator of PSR J1748−2446ad?
A.J Perez's user avatar
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1 answer
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Photon sphere in neutron stars

Just a simple question. Has neutron stars photon sphere as black holes? If the answer is yes, what is the radious and why?
Gabriel Palau's user avatar
6 votes
1 answer
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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 ...
uhoh's user avatar
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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 ...
哲煜黄's user avatar
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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 ...
Alan Gee's user avatar
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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,...
Victor Stafusa - BozoNaCadeia's user avatar
4 votes
1 answer
249 views

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 ...
Junaid Ihsan's user avatar
1 vote
1 answer
215 views

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 ...
Alan Gee's user avatar
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9 votes
1 answer
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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 ...
Junaid Ihsan's user avatar
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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 ...
Autodidact's user avatar
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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 ...
uhoh's user avatar
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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 ...
Kavin Ishwaran's user avatar
5 votes
3 answers
2k views

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 ...
topotamadre's user avatar
2 votes
1 answer
55 views

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 ...
Kurt Hikes's user avatar
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15 votes
1 answer
491 views

How would a cooled down neutron star look when illuminated?

Assume we have a neutron star that has cooled down so far that it no longer emits visible light. If we illuminate it with a powerful external light source, what would it look like? Would it reflect ...
cuckoo's user avatar
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12 votes
2 answers
2k views

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 ...
zucculent's user avatar
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5 votes
3 answers
2k views

What is the smallest possible radius for a neutron star?

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 ...
Donald Blake's user avatar
7 votes
2 answers
327 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 ...
Young Kindaichi's user avatar
3 votes
0 answers
56 views

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, ...
zucculent's user avatar
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5 votes
0 answers
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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 ...
zucculent's user avatar
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2 votes
0 answers
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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 ...
Alex's user avatar
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11 votes
1 answer
1k views

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 ...
zucculent's user avatar
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5 votes
1 answer
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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 ...
uhoh's user avatar
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1 vote
2 answers
156 views

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.....
Kurt Hikes's user avatar
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4 votes
1 answer
676 views

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 ...
Alex's user avatar
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3 votes
0 answers
60 views

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 ...
Prallax's user avatar
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-2 votes
2 answers
157 views

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 ...
Alex's user avatar
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7 votes
2 answers
310 views

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 ...
Deschele Schilder's user avatar
1 vote
1 answer
188 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....
uhoh's user avatar
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4 votes
3 answers
305 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 ...
Giovanni's user avatar
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4 votes
1 answer
817 views

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, ...
Kurt Hikes's user avatar
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