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Neutron Star formation Entropy

When a neutron star forms, is its entropy lower than when it was in the form of the star core. In the case of a black hole the entropy becomes the surface area, so what happens in a neutron star ...
Roghan Arun's user avatar
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3 votes
2 answers
70 views

Massive star evolution leading to white dwarf?

Is it possible that a star with an initial mass greater than $12 M_\odot$ loses so much mass in the giant phase that it eventually becomes a white dwarf? If it is possible, what constellation or ...
gamma1954's user avatar
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Why can we not describe matter as an ideal gas when the gas is degenerate

When a low mass stars core mostly consists of helium (after years and years of fusion reactions) its thermal pressure decreases and so the core gets denser due to gravitational pressure. Why is it ...
selin's user avatar
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0 answers
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How fast is the naked-eye visible transition of a main sequence star to a giant? [duplicate]

I know the evolution of a main sequence star to a giant is a process that takes millions and millions of years, but how fast is the VISIBLE change? Basically, will our sun, for example, slowly grow to ...
blacktopshaman's user avatar
7 votes
2 answers
192 views

Why are black holes sometimes formed without supernovae?

I've heard that very massive stars can sometimes collapse into black holes without creating supernovae. How does this happen? (I suspect it's something to do with the relative lack of Urca process ...
blademan9999's user avatar
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0 votes
1 answer
37 views

Difference between star formation rate and star formation history

When we speak about galaxies evolution, what is the difference between the star formation rate and the star formation history?
Daniele Zambetti's user avatar
3 votes
1 answer
102 views

How many type II supernovae are there per stellar mass formed?

I have been searching for the number of type II (core-collapse) supernovae per unit of stellar mass formed. It is my understanding that a star must have an initial mass of at least 8 times and no more ...
sav's user avatar
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1 vote
1 answer
174 views

Would a black hole instantly form when a neutron star slips below the phantom event horizon?

So lets say we have a neutron star that is just few inches away from the phantom horizon and only needs 500 kg before collapsing. So lets say hypothetically that a ship that is designed to survive the ...
Roghan Arun's user avatar
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9 votes
2 answers
1k views

Why don't less massive stars explode in form of supernovas?

I'm a high school student with a question about supernovas and the life cycle of stars. I understand that supernovas occur in massive stars when they run out of fuel and collapse, resulting in a ...
Authentic Melody's user avatar
2 votes
2 answers
230 views

Can a massive star become a red giant more than once?

Massive stars may undergo multiple fusion processes as they near the end of their lifespans. Our sun will eventually start fusing helium in its inner core so that carbon is formed. As this occurs, the ...
user12277's user avatar
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14 votes
3 answers
3k views

Is it possible to tell the difference between a young star that is just "big" and an older red giant?

I read the Wikipedia page for one of the biggest known stars, UY Scuti, and was curious to see the age of the star isn't really known at all. When a star's hydrogen fuel is exhausted, it starts ...
MFerguson's user avatar
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Pair-instability supernovae: how does it happen?

How does the formation of electron positron pairs increase the energy density and softens the EOS? I trrying to understand the pair instability supernova. In many texts and articles, it is written ...
Debasish Dutta's user avatar
5 votes
1 answer
34 views

Why is the common envelope ejected in some accretor-donor systems?

As an example, let us consider a binary system of a neutron star and an evolved star (e.g. red giant) that has expanded, filled its roche lobe, and started the mass transfer onto the neutron star. ...
Gianluca's user avatar
0 votes
2 answers
134 views

How hot is the core of a star just before it collapses to form a black hole?

Is the core of a star still hot as the star collapses under its own gravity?
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1 vote
1 answer
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How could have Boson Stars formed in the universe at all?

Boson particles have been predicted by some to have been able to form stars known as Boson Stars. I am curious as to how these stars could have formed given that Boson particles are not truly affected ...
Kaleb Metke's user avatar
1 vote
0 answers
21 views

How long does the expansion last?

It is known that when a main sequence star consumes about 10% of the central hydrogen, the external envelope starts to expand leading the star to the phase of a red giant. How long does this expansion ...
mattiav27's user avatar
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1 vote
1 answer
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Why do elliptical galaxies not have large proportion of blue stars?

In an article it was given that elliptical galaxies are also formed when a spiral galaxy experiences continuous star burst thus depleting it's gas. So if this is correct than why do elliptical ...
25 Simran Tiwari's user avatar
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0 answers
33 views

Does a star that is far from any galaxy tend to rotate slower?

I'm wondering whether the rotation of a galaxy and the buffeting of the gas and dust within it by light and stellar wind and pressure waves makes nebulae or gas clouds in galaxies have more angular ...
Matthew Christopher Bartsh's user avatar
3 votes
1 answer
64 views

Do stars lose spin angular momentum, to planets, radiation, or gravitational waves, or in some other way get a longer period?

A spinning star is throwing off stellar wind, and electromagnetic radiation, which might be carrying away angular momentum, so that the star loses angular momentum, and its angular momentum per unit ...
Matthew Christopher Bartsh's user avatar
3 votes
1 answer
77 views

Evolution into a main sequence star

I was reading the following from the textbook An Introduction to Modern Astrophysics by Bradley W. Carroll Dale A. Ostlie, "Due to the onset of the highly temperature-dependent CNO reactions, a ...
Aravind Madhavan's user avatar
2 votes
2 answers
69 views

How can we be sure that degenerate stellar matter does not bring up emergent phenomena not considered during their theoretical analysis?

With the astrophysical predictions on stellar evolution (which I admit I am not familiar with in detail) I always ask myself how we can be sure that they are correct although they are extremely ...
oliver's user avatar
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2 votes
0 answers
104 views

Inner and outer orbital limit of planets in single-star systems

I am trying to find a rough cut-off of the inner and outer orbits of native planets around a single star. I know about the Roche limit and Hill Sphere, but these are not the limits I am looking for. I ...
Selewirre's user avatar
0 votes
1 answer
207 views

Energy released from forming a black hole?

Gravitational collapse release potential energy, in some cases a huge amount of it. In the case of a black hole, that collapse goes to "infinity" which suggests the release of "infinite&...
BCS's user avatar
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6 votes
1 answer
462 views

A question regarding water and a possible proton-proton chain reaction

I believe it is the case that stars as low as about 0.08 solar masses undergo the proton-proton chain reaction. So if you were to have a gas of more than about that mass of hydrogen in a location of ...
Rory Cornish's user avatar
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1 answer
46 views

When a star loses temperature its matter loses KE so does it mean the star's gravity weaken?

When a star loses temperature its matter loses KE so does it mean the star's gravity weaken? The question is based on Einstein's field equation which states that energy also contributes in space-time ...
Janko Bradvica's user avatar
4 votes
2 answers
148 views

When Sun was forming and before nuclear reactions inside the core what should have been its surface temperature?

When the Sun was forming and before all the nuclear reactions started inside its core, what should have been its surface temperature (only due to gas friction)?
Janko Bradvica's user avatar
2 votes
1 answer
63 views

In the far future, when the sky is devoid of stars, will a sufficiently advanced civilization be able to discover the big bang [closed]

In the far future, when most of the stars have expanded away and the only ones visible in the observable universe are those in the host galaxy, will there be any obvious clues (assuming there are no ...
Foamteapot's user avatar
2 votes
2 answers
113 views

Rotational energy of stellar remnants

The theoretical maximum rotational energy a black-hole can have is 29% of its rest mass. We've often observed remnant black-holes spinning at nearly the speed of light. From this we conclude that ...
Will Jeremijenko's user avatar
-3 votes
1 answer
1k views

What is the process of star formation? [closed]

What is the process of star formation and what happens to stars after their death?
snowballCode's user avatar
3 votes
0 answers
31 views

Evaporation of a gravitationally-bound spherical cloud of a warm ideal gas in a vacuum

It seems that for any gravitationally bound system with a very large number of atoms/particles, there will always be some particles that manage to achieve escape speed and ultimately leave the cloud. ...
Roger Wood's user avatar
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1 vote
0 answers
44 views

Star formation rate in different galaxies

I was looking for some scale to compare my result of star formation rate and see if it is moderate or high or low. But I couldn't find any scale. Is there any paper related to such scale where Star ...
Sagar Rawal's user avatar
1 vote
0 answers
409 views

How does metallicity affect stellar evolution?

The main sequence evolution of a solitary star depends most of all on its initial mass. Other factors influencing its evolution are the initial metallicity, rotation and magnetism. Question: how does ...
gamma1954's user avatar
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2 votes
1 answer
68 views

Death of Stars and Red Giants [duplicate]

As a matter of fact, I was learning stellar astrophysics where I couldn't understand the chain of events at the time of death of stars, Once the hydrogen fuel core is exhausted, the stars start ...
Kshitij Kumar's user avatar
6 votes
2 answers
318 views

Why don't baby black holes give off a lot of Hawking radiation and vanish before having the chance to grow?

Is it because they eat more than they eject? Or something else? Edit ------- I mean black holes which have just started forming from stellar collapse. Should had mentioned this. Edit 2 ----- When you ...
Midovaar's user avatar
  • 159
1 vote
3 answers
237 views

How big should a star be to turn into a black hole?

My initial calculations show that if the radius of a star $-$ with a uniform mass density of $\rho$ $-$ is greater than $\frac{c}{2\sqrt{\pi G\rho/3}}$, the star would collapse into a black hole. ...
Mohammad Javanshiry's user avatar
1 vote
0 answers
29 views

Why does nature have higher atomic nuclei if Iron(Fe) has higher binding energy per nucleon? [duplicate]

From the binding energy per nucleon (B.E./A) vs atomic number (Z) we know that Iron (Fe) is most stable nuclei in the nature. Here comes the question that if nature has found the stable nuclei then ...
robert froast's user avatar
2 votes
2 answers
94 views

Could you know in advance specifically when a star will go supernova?

I've been thinking about star trek 2009 and star trek Picard in which they happen to talk about a sun inside a fictional solar system which goes supernova destroying a particularly important planet to ...
The victorious truther's user avatar
1 vote
3 answers
382 views

Why don't main sequence stars continuously expand?

I understand main sequence stars become subgiant when hydrogen is depleted in their cores and they start hydrogen shell burning. But I don't understand why this process is divided into two distinct ...
Vitor Machado's user avatar
11 votes
1 answer
467 views

Mass gap between neutron stars and black holes

From the detection of gravitational waves in GW190814, the merging of a 2.6 solar mass compact object with a heavier object has been inferred. The lighter object is in the "mass gap" between ...
gamma1954's user avatar
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0 votes
1 answer
84 views

What causes highly compacted matter to collapse into a black hole? [duplicate]

"The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole". Why does this happen? I mean, why something finite (like the core of a very ...
NumLock's user avatar
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1 vote
0 answers
31 views

When do planets formed via core accretion in a proto-planetary disk stop gaining mass?

I was just trying to go over some of the contents in my exo planets course and wanted to know that if all the planets that form via core accretion continue to attract all the dust in a proto-planetary ...
Vishal Jain's user avatar
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0 votes
1 answer
369 views

What will be the mass of the sun when the core is depleted of hydrogen about 5 billion years from now?

Our sun converts 600 million tons of H to He every second, that is 5 million tons of matter into energy through nuclear fission. However, as the core of the sun continues to shrink the outer layers of ...
Tushar Sharma's user avatar
4 votes
2 answers
1k views

Understanding the Chandrasekhar limit for white dwarfs and its relation with supernovas

So if I understand correctly, the Chandrasekhar limit ($\sim 1.4 \ M_{\odot}$) is the maximum mass that a white dwarf can have. Beyond this mass, the degeneracy pressure of the electrons can no longer ...
Guillermo Franco Abellán's user avatar
20 votes
3 answers
7k views

Why do main sequence stars get bigger and more luminous as they age?

As stars age, the concentration of hydrogen in the core decreases, which lowers the power output, causing an imbalance between outward radiation pressure and inward gravitational pressure. This causes ...
never took courses but why's user avatar
3 votes
1 answer
207 views

How long from star collapse to supernova explosion?

According to some reports, Betelgeuse might "be ready to explode into a supernova". It's luminosity has decreased "considerably" in the recent weeks. If we consider the "stable period" as that when ...
luchonacho's user avatar
3 votes
1 answer
383 views

Evolution of red dwarf stars

While low mass stars (initial mass approximately $0.1 M_\odot$ to $0.8 M_\odot$) are quite numerous, their evolution seems to draw relatively little attention. The lower central density and ...
gamma1954's user avatar
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6 votes
2 answers
451 views

Why do later fusion stages in a star last shorter?

When most of the hydrogen in the core of a massive star has fused to form helium, the next fusion stages (helium, carbon, neon, oxygen, ...) produce less and less energy in a single fusion reaction. ...
gamma1954's user avatar
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0 votes
0 answers
25 views

Existence and evolution of P-type "asymmetrical binaries"

I'm not sure how those are called so let me explain what I mean by "P-type asymmetrical binaries" - I'm thinking of two stars of very different masses (originally) that orbit each-other fairly closely....
Rosh's user avatar
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0 votes
2 answers
136 views

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 ...
Manoj Payardha's user avatar
0 votes
1 answer
85 views

Temperature function for stars?

I was thinking that for a star to be stable, the rate of energy emittance through a shell of radius r is constant, otherwise there would be a buildup of energy which would change the temperature and ...
Brain Stroke Patient's user avatar