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Questions related to the evolution of stars.

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Are there simplified M-L, M-R, and lifetime equations for non main sequence stars?

To give some context - I am trying to create a simple program that outputs the stellar properties of a star when given its initial mass and current age. e.g. Input Initial Mass = 2e30kg Age = 4.6 ...
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0answers
36 views

Why does D4000 affect stellar age?

From my understanding D4000 is a ratio between the 'flux densities between 4050 and 4250 Angstroms and that between 3750 and 3950 Angstrom', from Poggianti et al (1997). However I do not understand ...
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1answer
356 views

Why is H_delta prominent in type A stars?

I understand factually that H$\delta$ lines are most prominent in type A stars and less so in more extreme types of stars on the H-R diagram. However I was wondering the reason for why they are not ...
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1answer
48 views

What are the equations governing stellar evolution (Luminosity, Mass, Temperature, Radius)

I'm looking for ('simplified') equations governing stellar evolution. Especially how mass, luminosity, temperature and radius of a star change during it's lifetime. As well as equations which tell you ...
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3answers
6k views

Where did the Sun get hydrogen to work with if it is in the 3rd generation of stars?

As I see here, the Sun belongs to the Population I group of stars, which is the 3rd generation of the stars in our universe. 1st generation stars are Population III, 2nd generation are Population II, ...
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1answer
27 views

Secondary maximum in SNIa lightcurves for near infrared

Type Ia supernovae (SNIa) are thermonuclear supernovae that generates a lot of Nickel 56 which emits photons while disintegrating. How is the secondary maximum in lightcurves for reddish bands (see ...
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0answers
77 views

What fraction of a star's hydrogen store will be fused over its lifespan?

A main sequence star will fuse some of its hydrogen, but not all. In massive stars ($>1.5M_\odot$) the core is convective but the rest of the atmosphere radiative and hence does not mix much: as it ...
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1answer
46 views

What factors makes a star big in size(Physically)?Is the size of the nebula a relevant factor?

(Our sun compared to some of the known stars) I know that the star is born in a nebula.Do only a extremely gigantic nebula give rise to large-radius star or is there any other factors related?
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0answers
34 views

Doubt about star formation [duplicate]

When a star runs out of hydrogen, it either goes through supernova or forms white dwarf and planetary nebula. So there should not be much hydrogen left to form a new star in the nebula. So how new ...
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1answer
23 views

Stellar electromagnetic signatures

By using only the electromagnetic signature of a star, could a star be distinguished with reliable accuracy from any other star? To elaborate a little, say we have a collection of about 200,000 stars. ...
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0answers
39 views

pp-Chain reactions involving $^{3}_{2}He$ - differences in S-factor

So I was looking at the pp-chain reactions that take place inside stars in a bit more detail. I got confused about the massive differences in reaction efficiencies concerning two reactions $^{3}_{2}He$...
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1answer
65 views

Question about stellar remnants

I know that after a star undergoes the process of mass loss, depending on the mass of the core the stellar remnants gets converted into a white dwarf star, neutron star or a black hole. Hence, if the ...
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2answers
220 views

Can someone explain this diagram showing the spectral type distribution of bright stars

Can someone explain this diagram? The text is in Dutch, free translation: "You are given a graph: a histogram of the 10 000 most apparent bright stars. Explain 1, 2 and 3." The fact that the number ...
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1answer
228 views

Why do type Ia supernovas produce more iron than type II

My course book on astronomy states the following. Older stars seem have higher oxygen abundances than iron. Explanation is that back in the days when these older stars were being formed type II ...
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1answer
130 views

What affects the evolution curve of a star's luminosity as a function of time?

Take a star of a given mass (say $1.0\ \mathrm{M_{\odot}}$ or $1.1\ \mathrm{M_{\odot}}$), what affects the star's luminosity as a function of time and how much? (metallicity?, rotation?) It seems to ...
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2answers
179 views

Appearance of sun at geologic past

After origin of Earth ( 4.54 billion years ago ) to today; what are the changes through-which the sun undergone with time? , ( if seen from Earth. ) I'm doing some palaeobiology-landscape rendering; ...
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1answer
216 views

Concerning the “Lithium test” for Brown Dwarfs

Both low-mass PMS (pre-main-sequence) stars and young brown dwarfs can fuse lithium in their cores and the lithium can be depleted throughout the star/brown dwarf very quickly. Wiki. Then the Li I ...
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4answers
210 views

How do we know how the Sun (or any star, for that matter) will evolve?

The evolutionary path of the Sun has been described in some detail, and, subtle differences aside, it's been described as such for decades - the Earth-engulfing red giant stage, the helium flash, etc.....
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3answers
562 views

How much of carbon, sodium, silicon, and magnesium does the Sun have?

I've just begun learning of Astronomy and I can't figure out why any stars would begin their life with such elements if nuclear fusion hasn't created them. Don't all stars begin life as Hydrogen? I ...
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1answer
451 views

Relationship between metallicity and color? Should Pop. I stars be blue?

I have found in numerous places such as this website: http://burro.astr.cwru.edu/Academics/Astr222/Galaxy/Structure/metals.html or in "Introduction to Stellar Astrophysics" by B. Carroll, that state: ...
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1answer
90 views

Neutrino producton rate over time

Has the rate of neutrino production in the universe varied over time? Are there more or less being created now against the early days?
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2answers
502 views

Mass of black holes compared to parent star

What is the range of percentage mass of parent star left in a stellar black hole directly after its formation? What factors determine this number for a specific case?
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1answer
277 views

How do we know a star's age based on its spectrum? [duplicate]

A star's nearby environment may give clue to its age. Different stellar type have different spectral features. If we just have its spectrum, how do we know its age? For example, a star may be born ...
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2answers
483 views

What is the final destination of a neutron star?

As I understand, neutron stars are born as extremely bright, extremely fast spinning cores of stars dying in a supernova. However, several websites tell me that within a course of a few years, the ...
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1answer
128 views

Could non-supernova carbon, oxygen, or silicon flashes be observed?

I was reading about the helium flash, the short but sudden onset of helium fusion in certain red giant stars. As I understand, the upper (nondegenerate) layers of the star absorb the energy as they ...
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1answer
8k views

How can there be 1,000 stellar ancestors before our Sun?

I've heard from a few sources recently that the Sun is a 1,000th generation star, meaning it had a thousand stars that came before it based on its heavy-element content. I understand that earlier ...
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1answer
315 views

What are the possible solutions to the Red Supergiant problem?

I have recently come across this so called "Red Supergiant problem" in the literature, a phrase that was coined by Stephen Smartt in 2009 in reference to why red supergiants with masses ∼16-30M⊙ have ...
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1answer
492 views

Redshift to calculate age of stars

In multiple articles I have seen the age of a star, within the milky way, referred to as its redshift (typically denoted by $z$). I know that $z$ can be calculated as $z=\frac{\lambda_{obsv} - \...
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1answer
78 views

Metalicity and age of bulge stars vs halo [duplicate]

From what I understand of current models, the bulge of the galaxy formed first, and thus, would contain older population II like stars. Currently, however, the halo has a higher population of stars ...
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1answer
555 views

Why can't neutron stars ignite and explode?

Beyond the Chandrasekhar limit, white dwarfs become extremely hot. As a result, previously unfusable carbon can become fusable, causing nuclear reactions. This leads to thermal runaway and ultimately ...
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1answer
410 views

Stellar mass limits for Neutron Star and Black Holes

Don't hate on me if I am asking a very basic and straightforward thing. I have a few questions about black holes and neutron stars. What is the mass range (in terms of solar masses) for a main ...
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1answer
382 views

Why does shell fusion produce more energy than core fusion?

Stars go from the main sequence phase to the red giant branch due to the depletion of hydrogen in the core. As a result, the star contracts and shell hydrogen fusion begins, which apparently produces ...
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1answer
1k views

Why is the Sun's brightness and radius increasing, but not its temperature?

On the Sun's article on Wikipedia, there is an image showing how the Sun's brightness, radius and temperature have changed over time: For the past (and next) few billion years, I see the luminosity ...
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1answer
62 views

If a star were to suddenly lose nearly all of its stored heat, would it be able to return to its normal state? [closed]

If not, would it be possible to approximate the maximum heat energy a star could lose before the change became irreversible?
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4answers
1k views

How could a neutron star collapse into a black hole?

White dwarfs usually do not collapse, as they have electron degeneracy pressure due to the Pauli exclusion principle. However, if one accretes mass beyond the Chandrasekhar limit, it is energetically ...
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1answer
162 views

Description of Henyey tracks on wikipedia incorrect?

So, if you search for Henyey tracks on wikipedia (I know, the shame of it!) you will come across this statement: The Henyey track is characterized by a slow collapse in near hydrostatic ...
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1answer
214 views

Why do PMS stars on the Hayashi track remain at a constant temperature while they contract?

Why do pre-main-sequence stars on the Hayashi track remain at a constant temperature while they contract? I've read the Wikipedia article, so no need to repeat the derivation. What I took away from ...
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1answer
164 views

Why do proto stars on the Hayashi track get dimmer as they contract?

Why do proto stars on the Hayashi track get dimmer as they contract? My expectation is that they would get hotter and brighter the more they contact. Why is this wrong?
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1answer
98 views

Gyrochronology?

I recently became aware of the work of the Kepler Cluster Study. In January of this year it was announced that a long awaited method of finding ages of "cool" stars is now available. This is huge and ...
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2answers
174 views

Temporal path through Hertzsprung-Russell diagram?

Is there graphic of typical temporal paths that stars take through the Hertzsprung-Russell diagram?
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2answers
162 views

Can any stars ever form supermassive black holes?

I heard that most supermassive blackholes are not formed by stars – in fact, we aren't even sure how they're formed. But could a star, with enough mass and low enough metallicity, form a supermassive ...
4
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1answer
626 views

Why do certain massive stars leave no remnants?

Mass and metallicity are the two main determinants for a star's fate. This is simple enough. What's more complicated is how exactly these determine the star's fate. For example, you can see in this ...
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3answers
2k views

Is a black hole a perfect sphere?

I know all about how black holes form and why their gravity is so strong. However, is the gravity equally powerful in all directions? Will the event horizon appear as a perfect sphere?
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2answers
2k views

What happens to oxygen produced on the Sun (or other stars)?

Through nuclear fusion, the Sun can (or at the very least, someday will) produce atoms of all elements up to and including oxygen. And in terrestrial chemistry at least, when you combine oxygen, ...
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2answers
509 views

How long does an over contact binary star system last?

I read recently about VFTS 352, an overcontact binary star system where both stars have roughly equal mass. All of the reports I've read (in mass-media type publications) have said that the system has ...
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3answers
136 views

Recommendation for learning about stellar astrophysics

I would like to know which are the best books to learn about stellar astrophysics at (just) graduate level. I have a basic formation in general astrophysics but I'm interested in learning about ...
3
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1answer
334 views

How massive does a main sequence star need to be to go type 1 supernova?

We know the mass a white dwarf needs to be. That's well defined by the Chandrasekhar limit, but before a main sequence star turns into a white dwarf it tends to lose a fair bit of its matter in a ...
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1answer
379 views

Why is metallicity important in the death of stars?

I always thought that mass was the sole determinant of a star's fate. Then I saw the table here. So why does metallicity influence a star's ability to become a black hole or neutron star? Does it have ...
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1answer
102 views

What's the bleeding-edge model for how Population III stars are born and evolve?

I'm trying to do a brief literature review to find out what the best current models for population III stellar evolution are. I was hoping that someone with more expertise in the area could perhaps ...
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2answers
83 views

Conflicting information about the star Delta Pavonis?

Delta Pavonis has about the same mass as the sun so I would think that the evolutionary path would be about the same (the mass is given as O.991 M(Sun)/ not sure how we get this so accurately). It has ...