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Questions tagged [stellar-evolution]

Questions related to the evolution of stars.

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Are there any kinds of binary pairings that haven't been discovered yet?

There are lots of possible objects. For simplicity's sake (i.e. to hide my ignorance) lets assume momentarily that there are only black holes, neutron stars, white dwarfs, brown dwarfs, red giants, ...
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Properties of low-mass stellar remnants vs the Earth

How does the Earth differ from a (low-mass) stellar remnant, which has stopped fusion and the outer layers of which have been blown away? Could a stellar remnant end up with a similar relative ...
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1answer
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Stellar nurseries in the “Shedding New Light on the Whirlpool Galaxy” video

Captions in the Hubble Space Telescope YouTube channel video Shedding New Light on the Whirlpool Galaxy say: (visible) Along the dark dust lanes, bright pink nebulae are the birthplace of new stars....
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Is the structure of crystalized white dwarf related to nuclear pasta?

There is news of an analysis of a large number of nearby white dwarfs revealing a "pile-up" at a certain point in their cooling which has been predicted to happen due to a phase change where nuclear ...
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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 (...
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3answers
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How long does it take for a white dwarf to cool to a black dwarf?

I was reading on white dwarfs, and I came across this sentence— Without energy sources, the white dwarf cools to a black dwarf in a few billion years.[1] However, when I looked into the Wikipedia ...
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How to convert Log(g) vs T_eff to y vs (v-y)?

I have a plot in Log(g) vs T_eff coordinates from my stellar evolution model. The parameters of the model are M=0.8 M_solar, [Fe/H]=-1.19, Y=0.245. I want to convert it to the y vs (v-y) coordinates (...
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45 views

Activity of M dwarf stars

Why are M dwarf stars the most active (in terms of starspots and faculae) of all stars?
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Compute the total stellar mass of galaxy with major influence of Red Giants luminosity

Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago If the luminosity in the B band (absolute magnitude in B-band is equal to -21.22) is dominated by ...
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1answer
35 views

From original burst, fraction of stellar mass still surviving on Main sequence

Suppose that all stars in this galaxy were born in a single major-merger burst event about 10 Gyr ago. From this original burst, I want to compute the fraction of stellar mass still surviving as stars ...
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1answer
61 views

Could population III stars develop directly into population I stars?

Hundreds of millions of years after the Big Bang, the very first stars began to form consisting of mostly hydrogen, a bit of helium, and maybe some lithium. These stars lacked any "metals" (elements ...
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What is the theoretical ages for Pop I stars

How old could population I stars theoretically be? What's the earliest they could have formed?
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Does a star fuse helium to beryllium on the main sequence?

When a star has finished fusing all its hydrogen into helium, it will then start fusing helium into beryllium and so on and so forth up until iron. When the star is fusing to beryllium, will the ...
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3answers
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Sun's Stellar Class at Birth?

The Sun currently has a stellar class of G2V. However, since its birth, the Sun has brightened significantly. What would the Sun's class have been when it was born ~4.6 gyr ago?
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Could Black holes forge heavier elements that have yet to be discovered?

Observations The heaviest elements known in abundance in nature are forged deep within stars. These elements are made possible by the high densities/pressures within the stars. Black holes are known ...
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1answer
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Stellar core mass as a function of metallicity

Using Hurley's 2000 paper on Single Stellar Evolution, I have graphed the core mass of a star at three stages as a function of metallicity, Z, for a chosen ZAMS mass: at the beginning of the HG (MS), ...
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1answer
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Is there a more modern/updated paper than Hurley's 2000 SSE?

I've implemented equations from Hurley's 2000 paper on Single Stellar Evolution (SSE) to model the stages of stellar evolution without having to use the full SSE code (or MESA for that matter). Is ...
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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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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
366 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
64 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
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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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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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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
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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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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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2answers
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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
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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
78 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
300 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
345 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
302 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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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
335 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
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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
765 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
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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
94 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
657 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
485 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
681 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
158 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
373 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
661 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
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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
679 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
481 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
470 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
2k 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 ...