Questions tagged [neutron-star]
Questions regarding a degenerate star that is mainly composed of neutrons.
177
questions
7
votes
1
answer
85
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\...
- 71
2
votes
1
answer
138
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?
- 123
6
votes
0
answers
93
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
107
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 &...
- 63
9
votes
2
answers
960
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 ...
- 23.3k
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 ...
- 415
4
votes
1
answer
137
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 ...
- 31k
5
votes
2
answers
979
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 ...
- 255
1
vote
0
answers
133
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?
- 11
1
vote
1
answer
92
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?
- 295
6
votes
1
answer
101
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 ...
- 31k
6
votes
1
answer
147
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 ...
- 275
1
vote
0
answers
31
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 $$
But taking into account that g will change ...
- 211
5
votes
1
answer
68
views
What is the spectral reflection curve of cold white dwarfs and neutron stars?
Suppose that I got a white dwarf and a neutron star and after some trillions of years their temperature are down to just a few °K so cold that they don't emit any appreciable black body radiation.
Now,...
5
votes
1
answer
230
views
Difference between NSBH and BHNS mergers
What's the difference between Neutron Star-Black Hole Merger (NSBH) and Black Hole-Neutron Star Merger (BHNS)? Are they the same names for the same events or is there any difference between them?
I ...
- 313
1
vote
1
answer
189
views
Is a black hole really a neutron star with a gravitational time dilation factor of 1.0
Here's why I'm asking.
The gravitational time dilation factor at the surface of a star or planet can be expressed as $$gr/c^2$$
In theory, the same equation should apply to the gravitational length ...
- 211
9
votes
1
answer
802
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 ...
- 313
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 ...
- 311
3
votes
1
answer
94
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 ...
- 31k
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 ...
- 2,625
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 ...
- 61
2
votes
1
answer
47
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 ...
- 4,179
14
votes
0
answers
287
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 ...
- 670
11
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 ...
- 1,698
5
votes
2
answers
1k
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 ...
- 51
7
votes
2
answers
231
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 ...
- 473
3
votes
0
answers
50
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, ...
- 1,698
5
votes
0
answers
66
views
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 ...
- 1,698
2
votes
0
answers
104
views
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 ...
- 621
11
votes
1
answer
940
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 ...
- 1,698
6
votes
1
answer
488
views
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 ...
- 31k
1
vote
2
answers
126
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.....
- 4,179
4
votes
1
answer
651
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 ...
- 621
3
votes
0
answers
50
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 ...
- 4,274
-2
votes
2
answers
106
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 ...
- 621
7
votes
2
answers
277
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 ...
1
vote
1
answer
162
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....
- 31k
4
votes
3
answers
220
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 ...
- 145
3
votes
1
answer
547
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, ...
- 4,179
15
votes
3
answers
2k
views
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 ...
- 31k
0
votes
1
answer
82
views
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}\...
- 6,474
1
vote
0
answers
78
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, ...
- 5,444
3
votes
1
answer
122
views
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 ...
2
votes
0
answers
103
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 ...
3
votes
0
answers
47
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. ...
2
votes
0
answers
86
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, ...
4
votes
1
answer
115
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......
- 4,179
2
votes
1
answer
108
views
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? ...
- 21
5
votes
1
answer
671
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 ...
- 5,444
1
vote
1
answer
105
views
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 ...
- 329