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Questions tagged [neutron-star]

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

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4 votes
1 answer
911 views

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 ...
4 votes
2 answers
436 views

What is the "hypothesized lower mass gap" between 2.5 and 5 solar masses?

Searching here for "mass gap" yields nothing yet. Penn State's Black hole or neutron star? LIGO-Virgo scientists find mystery object in 'mass gap' begins: When the most massive stars die, ...
8 votes
2 answers
1k views

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 ...
5 votes
0 answers
129 views

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 ...
15 votes
1 answer
501 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 ...
3 votes
3 answers
357 views

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 ...
6 votes
2 answers
1k views

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,...
1 vote
1 answer
102 views

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 ...
1 vote
0 answers
48 views

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 ...
4 votes
1 answer
323 views

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 ...
45 votes
2 answers
48k views

How does a neutron star collapse into a black hole?

We know the spectacular explosions of supernovae, that when massive enough, form black holes. The explosive emission of both electromagnetic radiation and massive amounts of matter is clearly ...
5 votes
1 answer
165 views

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 ...
0 votes
0 answers
84 views

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 ...
-2 votes
2 answers
158 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 ...
4 votes
1 answer
75 views

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 ...
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 ...
2 votes
1 answer
161 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 ...
14 votes
5 answers
2k views

Is it possible neutron stars are actual elements?

As you go up the periodic table (more protons), the ratio of neutrons to protons steadily increases as well. Are we sure there are absolutely no protons and electrons in a neutron star, or could there ...
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 ...
7 votes
1 answer
90 views

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\...
62 votes
3 answers
16k views

What is the hottest thing in the universe?

Straight from my 7 year old to you, exactly what it says on the cover: What is the hottest thing in the universe? To make it Stack Exchange-friendly, I'll add the following caveats: it should be ...
2 votes
1 answer
180 views

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?
5 votes
0 answers
115 views

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 ...
4 votes
1 answer
117 views

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 &...
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 ...
9 votes
2 answers
984 views

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 ...
21 votes
5 answers
4k views

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 ...
4 votes
1 answer
175 views

"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 ...
5 votes
2 answers
1k views

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 ...
0 votes
0 answers
158 views

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?
2 votes
0 answers
62 views

What methodology should be used to choose the correct model for origin of QPOs in X-ray astronomy?

In X-ray astronomy, quasi periodic oscillations (QPOs) are routinely shown by black hole and neutron star X-ray binary systems in their X-ray flux. Despite being strong and easily measurable signals, ...
1 vote
1 answer
129 views

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?
1 vote
2 answers
159 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.....
6 votes
1 answer
116 views

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 ...
4 votes
1 answer
129 views

Do neutron stars have something like a gamma-ray photosphere? Are gamma rays from below it limited more by the nuclei or electrons?

@RobJeffries' answer to Is there evidence of super-heavy elements in the x-ray and gamma-ray spectrums of neutron stars? includes the sentence: However, the only things that contribute to a neutron ...
13 votes
5 answers
4k views

Is there a possibility that a white dwarf can turn into a neutron star or a black hole?

I know that a white dwarf is supported mainly by electron degeneracy pressure and that if it gains more than about 1.4 solar masses from any source (such as a companion star or a collision), it ...
6 votes
1 answer
186 views

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 ...
1 vote
0 answers
42 views

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 ...
5 votes
1 answer
90 views

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,...
1 vote
1 answer
216 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 ...
4 votes
1 answer
250 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 ...
8 votes
1 answer
1k views

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 ...
9 votes
1 answer
822 views

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 ...
3 votes
1 answer
116 views

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 ...
3 votes
0 answers
177 views

What does "GPU-accelerated butterfly matched filtering over dense bank of time-symmetric chirp-like templates" mean? (GW170817)

A new analysis of gravitational wave (and other data) from GW170817 on 2017-Aug-17 has been published, strongly suggesting that the merger of two neutron stars resulted in a large, rapidly rotating ...
13 votes
2 answers
2k views

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 ...
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 ...
4 votes
3 answers
390 views

Could anything consume a small black hole?

Whenever I read about black holes, it is normally involving how they devour anything that comes too close... regardless of how big anything is. But what if it were a really small black hole vs ...
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 ...
9 votes
2 answers
412 views

Do the neutrons in neutron stars emit the radio waves?

Neutrons can, especially in extreme circumstances (and large concentrations) emit electromagnetic radiation. I specifically asked about this in Physics S.E. Has a free neutron ever been shown to ...