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Questions tagged [stellar-evolution]

Questions related to the evolution of stars.

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Comprehensive Stellar Evolution Article

Is there an article that comprehensively covers stellar evolution, from start to finish. I've found articles on this, one in an introduction to a stellar evolution model, and I am searching for more. ...
Astrovis's user avatar
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What do you call a protostar with more than 10 solar masses?

PMS Stars with less than 3 solar masses are T Tauri stars, and PMS stars between 3 and 10 solar masses are herbig ae/be stars, so what do you call a star with more than 10 solar masses? Is there ...
Astrovis's user avatar
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Hayashi Track vs Red Giant branch

Are the red Giant branch and the Hayashi track the same thing? After doing some research, I found some similarities between the two, such as both aree fully convective. However, the T Tauri phase does ...
Astrovis's user avatar
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2 votes
1 answer
215 views

Pure Lithium Star

Suppose by some miracle a large molecular cloud of pure lithium assembled itself in space, then gravitationally collapsed. What would the result look like? Would it be a star of some sort (fusing the ...
volcanrb's user avatar
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Question about a White Dwarf formula

I have a question regarding the White Dwarf radius formula given on wikipedia, in terms of what units I am supposed to use and what expected values of one variable would be. https://en.wikipedia.org/...
DanceroftheStars's user avatar
2 votes
2 answers
253 views

How to predict the radius of a Red giant

I am working on a sci-fi that goes over such a large length of time that I will be having stars dying out, and this raises a question that I would need to find an answer to. How can one predict the ...
DanceroftheStars's user avatar
6 votes
1 answer
585 views

Intuitive connection between the periods of oscillation of Betelgeuse and the elemental concentrations at its core? (Betelgeuse; Saio et al. (2023))

Preamble (yes it's long, but it's part of this question's premise, so need to spell it out) Dr. Becky's recent video New study claims Betelgeuse supernova IMMINENT (decades not centuries!) | Night Sky ...
uhoh's user avatar
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What are the primary astrophysical implications of a proposed mass of about 11 M⊙ for the SN 2023ixf progenitor?

The abstract of the arXiv preprint SN 2023ixf in Messier 101: A Variable Red Supergiant as the Progenitor Candidate to a Type II Supernova (itself recently "discovered" in the observatory) ...
uhoh's user avatar
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4 votes
1 answer
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What crystal structures are predicted for the crystalline phase of matter inside crystalizing white dwarfs? Does it depend on the carbon/oxygen ratio?

The abstract of Venner et al. (2023) A Crystallizing White Dwarf in a Sirius-Like Quadruple System includes the following: The location of HD 190412 C on the 𝑇eff − mass diagram implies it is ...
uhoh's user avatar
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Do stars become more metal-rich as they evolve?

Since we determine the metallicity of a star ([Fe/H] or Z) from surface emission, does this change as it ages? For instance, can a young star with a measured [Fe/H] of -0.02 have a higher value when ...
Jack R. Woods's user avatar
2 votes
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Radius and surface temp of red giant Sun [duplicate]

There is wildly conflicting information going around about the predicted parameters of the Sun as a red giant. The estimates for the radius vary from 100 to even 256 solar radii (with the larger ...
Adam Kamil Gola's user avatar
4 votes
2 answers
564 views

Trying to understand this graph (stellar activity)

I managed to trace this graph back to http://katjapoppenhaeger.com/?p=457. It's meant to show how stellar activity declines with time for different star types, and whilst I get the general idea, I don'...
Kazon's user avatar
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1 answer
161 views

Do red dwarf stars get dimmer over time, the opposite of most other main sequence stars?

It is common knowledge, for instance, that the sun has increased in brightness by roughly 40% since its formation... (The apparently early appearance of life has led to the 'Faint young Sun paradox', ...
Kurt Hikes's user avatar
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2 votes
1 answer
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Why are the largest stars, such as O-type or B-type, most likely to be in multi-star systems; while red dwarfs are least likely?

I was just reading about what percentage of stars in our galaxy and, perhaps, other galaxies are in binary systems (or trinary... etc.). Researchers keep going back and forth about whether or not most ...
Kurt Hikes's user avatar
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How much of the hydrogen in our sun will never participate in fusion? What about larger stars? [duplicate]

From what I gather, only red dwarf stars are fully convective, and will use up pretty much all of their hydrogen.... Is there a chart or list somewhere that shows the percentage of hydrogen that is ...
Kurt Hikes's user avatar
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1 vote
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Calculating the expected lifespan for a binary system

I’m doing some research work on finding a correlation between the mass of binary stars and their lifespan. I have methods to find the mass, and that department seems to be going fine, but is there a ...
Vedant 's user avatar
2 votes
1 answer
162 views

How can I Mathematically Calculate the Luminosity of a Post-Main-Sequence Star from Mass and Age?

So, I saw this question (which is quite old) and that's all well and good, but what if I need to (very) roughly calculate the luminosity of a star from the end of the main sequence? Let's assume that ...
isdi0's user avatar
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1 vote
1 answer
305 views

Lifespan of higher mass red dwarf stars

Wikipedia and the reference paper they are using offer some insights into the lifespan of smaller red dwarf stars (link). However it offers no insight as to what the projected lifespan of larger red ...
user1628056's user avatar
2 votes
1 answer
123 views

Modeling binary star using MESA

I'm trying to model a binary star using the MESA (Modules for Experiments in Stellar Astrophysics docs) code with an orbital period of 10 days with the scenario where mass transfers starts after the ...
Mac Fly's user avatar
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8 votes
1 answer
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Is Barnard's star an M4 red dwarf or an M0? Why is it called an M4.0V?

I have tried to figure this out, but cannot find an answer anywhere... Are, perhaps, astronomers unsure of its exact spectral class? (I have heard that red dwarfs are usually variable... to an extent....
Kurt Hikes's user avatar
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2 votes
0 answers
29 views

Equation describing Energy Transport due to Radiation in the interiors of stars

I am considering a very elementary stellar structure and I'm required to derive an equation to describe the energy transport due to radiation. The answer I am supposed to obtain is: $$\frac{dT}{dr}= -\...
Ambica Govind's user avatar
3 votes
1 answer
164 views

In the context of stellar nucleosyntheis, is Xenon-130 a primary or secondary isotope?

With the definitions: 'a primary isotope is any isotope which can be synthesised in a star which starts its life containing only hydrogen and helium', and a secondary isotope is any isotope which ...
ryani42's user avatar
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4 votes
1 answer
222 views

Can insolation affect stars?

Stars glow with (almost) a black body spectrum. The fourth-power dependency on temperature means that there are large differences in surface brightness between hotter and cooler stars. The coolest ...
Kevin Kostlan's user avatar
2 votes
1 answer
301 views

Does the mass-luminosity relation work for brown dwarfs?

There is a mass-luminosity relationship of the form $L \propto M^a$, where $a = 3.5$, that is is applicable to main-sequence stars. Is there a similar relationship that holds for brown dwarfs?
user avatar
8 votes
1 answer
1k views

What is it like to see a brown dwarf turn into a star?

Brown dwarfs/failed stars can actually become stars, if they exceed a mass limit of about 80 Jupiter masses. This is when the internal pressure and temperature at the core become high enough to ...
Alastor's user avatar
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7 votes
2 answers
339 views

Can a brown dwarf accrete enough mass from red giant to become a star?

Let's assume a brown dwarf is on orbit around a main sequence star. Than the star becomes a red giant. Let's assume the brown dwarf has "the right" orbit and can syphon matter from the red ...
Heopps's user avatar
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3 votes
0 answers
42 views

How can I calculate evolutionary timescales of low mass stars?

How can I calculate how long a star of a given mass will spend on an evolutionary branch before evolving off it? I'm thinking about the evolution of low mass stars from the subgiant branch to the red ...
Holly Bee's user avatar
7 votes
1 answer
475 views

Are all T Tauris on the Hayashi track?

Reading the definitions of T Tauri stars and the Hayashi track one can gather that: T Tauri stars are pre-main-sequence stars in the process of contracting to the main sequence along the Hayashi ...
Gabriel's user avatar
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3 votes
0 answers
132 views

What estimate can be made of the time before a change in the Sun's intensity would make the earth uninhabitable? [closed]

From observation of stars we know that there are many types of stars that evolve over time and change and this known as stellar evolution. Over time a star changes in its size and in the intensity of ...
Tyler Durden's user avatar
7 votes
1 answer
170 views

Do planets affect their stars beyond causing them to wobble?

Are there any situations in which the existence of a planet measurably affects its star, aside from orbital wobble? I am curious about possible ongoing affects, not stuff that happened during stellar ...
David Bailey's user avatar
2 votes
0 answers
55 views

The necessary conditions for driving winds with dust (Dust-driven Wind)

So lately I've read Intro to stellar winds (particularly chapter 7 Dust-driven winds) by Lamers & cassinelli, I forget how many times I've read this but I still don't really understand. So in the ...
aapnegara's user avatar
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10 votes
1 answer
962 views

What actually are line-driven winds?

I have read several books (viz. intro to stellar winds)/articles about stellar winds (dust-driven, line-driven, coronal winds), but still didn't understand the explanation. I understand that line-...
aapnegara's user avatar
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6 votes
0 answers
158 views

Source of information on density profile of a red giant star?

Is there a good source of information of the expected density profile inside a red giant star? I have read that when a star such as the sun has converted much or most of the hydrogen in its core into ...
PAUL MILENKOVIC's user avatar
3 votes
3 answers
170 views

What physical process can Metallicity(Z) of a galaxy tell us?

For example, if there is a galaxy and its metallicity increase or decrease from high redshift to present day (We can see it from simulation like TNG or EAGLE). What physical process we can know? ...
Jinning Liang's user avatar
3 votes
1 answer
349 views

Is there a general way to plot the evolutionary track of a star on HR diagram?

HR diagrams for stars are available on the internet and it is also easy to plot this for thousands of stars from their absolute magnitude and color index values (obtainable from any catalog). However, ...
Abdul Muhaymin -Free Palestine's user avatar
4 votes
1 answer
126 views

Stellar evolution temperature gradient - why the logarithm?

We define the adiabatic temperature gradient as $$\Delta_{ad}= \Big(\frac{\partial \log \mathrm{T}}{\partial \log \mathrm{P}}\Big)_{ad}$$ The goal of this gradient is to show how the temperature ...
Loika's user avatar
  • 177
4 votes
1 answer
416 views

Virial theorem, contraction, and stars getting hotter

So, for a homogeneous sphere made of ideal gas the virial theorem applies: $$E_{int}=-\frac{1}{2}E_{grav}$$ I have read that this implies that a star must get hotter when it contracts. I don't quite ...
Loika's user avatar
  • 177
5 votes
2 answers
131 views

Do large stars ignite then continue to increase in size, or do they ignite only once they grow larger?

My limited understanding of stellar formation is that a gas cloud condenses enough that various forces (just gravity?) eventually lead to enough pressure to ignite nuclear fusion. However, since stars ...
Michael Stachowsky's user avatar
4 votes
3 answers
630 views

Why does the gas cloud collapse in regions of high density?

Stars form when gas cloud collapse under gravity, becoming hot and subsequently initiating nuclear fusion. I have read that the collapse is triggered by density fluctuations, where regions of high ...
Rian's user avatar
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2 votes
2 answers
763 views

What is the relation between Kelvin-Helmholtz timescale and free-fall timescale?

What is the actual difference between these two timescales? Both of these timescales define the time for collapse when there is only gravity. Also, what does it mean by saying Kelvin-Helmholtz ...
Rian's user avatar
  • 503
4 votes
1 answer
1k views

What determines the temperature of a white dwarf?

Can someone please explain what determines the temperature of the white dwarf? Is more massive white dwarf hotter ? Also, is the density of a white dwarf always a constant?
Rian's user avatar
  • 503
6 votes
2 answers
276 views

Are Superluminous supernova and Hypernova the same thing?

Are Superluminous supernova and Hypernova the same thing? Is there any difference with their formation, luminosity etc?
Jack the Ranger's user avatar
17 votes
1 answer
664 views

Is stellar ignition all-or-nothing?

The boundary between brown dwarfs and stars is around 80 Jupiter masses. Only stars generate a self-sustaining hydrogen fusion, although brown dwarfs sometimes fuse lithium and deuterium. Is hydrogen ...
Kevin Kostlan's user avatar
1 vote
0 answers
70 views

Mass-age stellar phase diagram

The HR diagram is a sort-of "phase diagram" (in a very rough sense) for stars, where a particular star's location on the diagram says something about what "kind" of star it is. ...
realityChemist's user avatar
2 votes
1 answer
304 views

What kind of opacity should I use when I simulate stellar structure?

I am tring to simulate the evolution of a star. As we know, opacity plays an important role and has many forms like: free-free, bound-free, bound-bound, electron scatter. But I am confused about their ...
Jinning Liang's user avatar
2 votes
3 answers
1k views

Was the young Sun cooler or hotter than it is today?

Generally, astrophysicists say that the young Sun was only about 70% as warm as today, which leads to the alleged 'Faint young Sun paradox' about how a young Earth could have been as warm as it (again,...
Kurt Hikes's user avatar
  • 5,177
4 votes
1 answer
589 views

How much mass is lost in the red giant phase of a star?

The red giant phase of stars are relatively fast. How will this impact a star's total mass? Are there significant mass losses taking place when this happens? If so, do we know how much? The sizes of ...
Constantthin's user avatar
0 votes
0 answers
66 views

What are the exact properties and evolution of a star with 1.23 Solar masses?

I'm working on a project where the star at the centre of the planetary system is 1.23 Solar masses. What would it's properties and evolutionary track be (i.e. main sequence lifespan, length of the red ...
Cryoraptor's user avatar
7 votes
2 answers
343 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
2 votes
1 answer
64 views

How well defined are the elemental shells in evolved stars?

Most textbooks and popular science show highly evolved massive stars with an onion-like structure with layers or shells of different elements fusing. This is clearly approximate (as noted in the ...
Anders Sandberg's user avatar

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