Questions tagged [stellar-evolution]

The tag has no usage guidance.

Filter by
Sorted by
Tagged with
2 votes
2 answers
51 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 ...
user avatar
  • 7,114
2 votes
0 answers
33 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 ...
user avatar
0 votes
1 answer
69 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&...
user avatar
  • 1,085
6 votes
1 answer
424 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 ...
user avatar
  • 1,037
0 votes
1 answer
39 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 ...
user avatar
4 votes
2 answers
131 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)?
user avatar
2 votes
1 answer
54 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 ...
user avatar
2 votes
2 answers
72 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 ...
user avatar
-3 votes
1 answer
505 views

What is the process of star formation? [closed]

What is the process of star formation and what happens to stars after their death?
user avatar
2 votes
0 answers
16 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. ...
user avatar
  • 2,462
1 vote
0 answers
29 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 ...
user avatar
1 vote
0 answers
190 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 ...
user avatar
  • 875
2 votes
1 answer
54 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 ...
user avatar
6 votes
2 answers
274 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 ...
user avatar
  • 159
1 vote
3 answers
103 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. ...
user avatar
1 vote
0 answers
27 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 ...
user avatar
2 votes
2 answers
71 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 ...
user avatar
1 vote
3 answers
134 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 ...
user avatar
7 votes
1 answer
272 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 ...
user avatar
  • 875
0 votes
1 answer
54 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 ...
user avatar
  • 83
1 vote
0 answers
26 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 ...
user avatar
  • 1,307
0 votes
1 answer
136 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 ...
user avatar
1 vote
2 answers
398 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 ...
user avatar
19 votes
3 answers
5k 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 ...
user avatar
3 votes
1 answer
165 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 ...
user avatar
3 votes
1 answer
234 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 ...
user avatar
  • 875
5 votes
2 answers
179 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. ...
user avatar
  • 875
0 votes
0 answers
23 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....
user avatar
  • 21
0 votes
2 answers
103 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 ...
user avatar
0 votes
1 answer
38 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 ...
user avatar
0 votes
2 answers
77 views

What conditions provide the oldest star?

If we define the start of the lifetime the protostar and the end of the lifetime a red giant (at max volume), what conditions would make this time the longest when the star was first formed and ...
user avatar
  • 2,563
0 votes
0 answers
306 views

M3 globular cluster: simple age determination

For my pre-university pupils I would like to find a simple way to determine the age of the globular cluster M3 using a colour-magnitude diagram (CMD, B-V horizontal axis and apparent visual magnitude ...
user avatar
  • 875
15 votes
1 answer
2k views

How do neutron star binaries form?

Do neutron star binary systems come from previously active-star binaries, where where both stars have gone supernova and left behind neutron stars that are still in orbit? Or do they form when two ...
user avatar
  • 3,060
2 votes
1 answer
91 views

If I add more mass to a red giant, will it become a supergiant?

Let's say I have a red giant. If I start dumping more matter onto it, will it eventually become a red supergiant? I'm guessing the answer is "yes" because when I see this covered in textbooks, they ...
user avatar
  • 16.4k
0 votes
1 answer
49 views

Why does a drop in gravitational energy result in star contraction

Consider a gas cloud that is radiating away heat. From virial theorem we see that if the cloud radiates away heat and loses energy this will cause its gravitational energy to drop. Why does this mean ...
user avatar
  • 886
0 votes
0 answers
97 views

How is black hole formed after a supernova explosion?

Does all the mass of a core collapsing star get scattered during a supernova explosion? If it does, then how can a black hole be formed without any remaining mass? Or are there remnants of the star ...
user avatar
1 vote
0 answers
42 views

Strength of core-envelope coupling in stars

For a star with a given Zero-Age Main Sequence (ZAMS) mass, as a function of metallicity how strongly is the star's core coupled to its envelope? I understand that the core-envelope boundary is only (...
user avatar
0 votes
1 answer
111 views

When a star undergo collapse in a binary system what effect it has on its companion star? [closed]

when a star in its lifetime fuses up all its hydrogen and then collapse under gravitational force, till the temperature inside become high enough to restart the fusion of helium and radiation pressure ...
user avatar
  • 165
0 votes
0 answers
91 views

Why does a star with its core collapsing and about to undergo a supernova, explode, instead of rapidly collapsing all of its matter into a black hole? [duplicate]

I am guessing this has something to do with density. I would assume that a massive star that has its core collapsing would be a prime candidate for having its core turn into a black-hole. If the ...
user avatar
0 votes
1 answer
336 views

What causes a supernova explosion?

I know similar questions have been asked and answered. However, it is still not clear to me, so please bear with me if this is duplicate to some extent. The explanation goes like this - the core ...
user avatar
  • 4,423
4 votes
0 answers
57 views

Do stellar model luminosities include neutrino losses?

I have had a sudden crisis in my understanding of the published outputs from stellar evolutionary model calculations. Usually these models output a "luminosity" that one can then use, along ...
user avatar
  • 111k
0 votes
0 answers
23 views

What is the process that leads to the volume expansion of the outer layers of a star when it becomes a red giant? [duplicate]

If a main sequence star runs out of hydrogen fuel in the core, the core collapses because of its own gravity, but what exactly leads to the expansion of the outer layers of the star when it is ...
user avatar
  • 127
1 vote
1 answer
291 views

The PPI Chain is composed of 3 steps: Does only the 2nd step release energy?

The PPI chain is \begin{align} \rm\ ^1H + {}^1H &\rm\rightarrow {}^2D + e^+ + \nu_e \tag 1 \\ \rm\ ^2D + {}^1H &\rm\rightarrow {}^3He + \gamma \tag 2 \\ \rm\ ^3He + {}^3He &\rm\rightarrow {...
user avatar
  • 613
2 votes
0 answers
55 views

Jupiter's formation

Two days ago i went to a mathematics conference where there was a paper presented on Jupiter's formation via disk-instability model. I know that there are two different theories for the formation ...
user avatar
  • 145
5 votes
1 answer
223 views

Why does the $\rm H$-burning Shell do the $\rm CNO$ cycle instead of the $pp$ Chain?

A star that initially produces energy through the $pp$ Chain will eventually exhaust its Hydrogen leading to a core contraction in order to increase the temperature to generate again nuclear reactions....
user avatar
  • 613
14 votes
3 answers
853 views

Does the Virial Theorem apply to degenerate matter?

I am trying to understand how the degenerated He core progressively increases its temperature as the star moves up through the Red Giant Branch. A well-known property of the degenerate He core is ...
user avatar
  • 613
0 votes
2 answers
249 views

How can a red dwarf have such an immense lifetime?

I understand what a red dwarf is, and that it is dominated by convection. But I still don't understand how the fusion processes in such a tiny star can keep going for the immense time predicted. ...
user avatar
  • 4,087
1 vote
2 answers
198 views

Why the He core gets hotter and hotter? Is it because it shrinks?

I know that after a star in the main sequence runs out of H in the core, it will start burning H in the shells surrounding the (now) He core. (1) Why now the Hydrogen shells are hot enough for ...
user avatar
  • 613
7 votes
2 answers
941 views

Can a hydrogen cloud directly collapse to form a black hole?

Does a cloud (essentially a nebula) have to turn into a star or can it directly become a neutron star/black hole? I might've read somewhere that some primordial black holes might have formed this way, ...
user avatar
3 votes
1 answer
117 views

Star formation confusion

If gravity is really a weak force compared to other forces, then how does gravity pull hydrogen atoms in a nebula to from stars. I understand that hydrogen is in atomic or in the molecular state in ...
user avatar