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Questions tagged [stellar-population]

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Regarding the phase space density of stars and the Maxwell-Boltzmann distribution

I was reading a paper where the authors effectively made the following equality when talking about stellar populations: $$\frac{\mathrm{d} N_* }{ \mathrm{d} m_* \mathrm{~d}^3 \mathbf{x} \mathrm{d}^3 \...
Matrix23's user avatar
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Stellar classification: Luminosity class

So in the astrophysics textbook by Carrol and Ostlie, when the luminosity class is discussed, it has such a sentence "The ratio of the strengths of two closely spaced lines is often employed to ...
ABC's user avatar
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What is the local stellar number density?

Is it just me or does this paper, while providing a great equation for the behaviour of the general stellar number density, never actually give a value for the local stellar number density $\rho(R={\...
Dyaus_Pitar's user avatar
3 votes
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Where are all the Population III galaxies?

We can now see back to 400 million years after the Big Bang. Yet we still haven't seen any Population III galaxies. Why is this? How do metal-rich galaxies evolve in just 400 million years?
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Dyson Sphere Structures [closed]

In a type II civilization we may need to harvest the energy of neighboring stars. Freeman Dyson gave an interesting point of view that we could invent a megastructure to harvest this type of energy. ...
Dendi Suhubdy's user avatar
1 vote
2 answers

Why has the amount of star formation in the Universe decreased over time?

If you like, refer to my old question from the last year, about star formation rates and their declining, answered by Rob Jeffries. I'm now examining why this process happens. It appears that in ...
Hatmix5's user avatar
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Has the number of new stars born decreased over time?

Has the number of new stars being formed decreased at all over the age of the universe? Would this be because the average density of the universe is decreasing due to the expansion of the universe, it ...
Hatmix5's user avatar
  • 383
4 votes
1 answer

Is there a way to tell what centile of the overall sample a star's mass is in?

One hears that hyper-giant stars like Eta-carinae represent the upper bound on stellar mass at about 130 solar masses. At the lower end there are red dwarfs with as little as 0.075 solar mass. You ...
ben's user avatar
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6 votes
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Are stars getting more metal-rich, less massive and shorter-lived with cosmic time?

A star produces energy through nuclear fusion with the 2H and 3H isotopes to create 4He for example. I read that there is a mass loss of 0.018884 (in atomic mass units). Of course this mass loss is ...
Hatmix5's user avatar
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8 votes
1 answer

Could we tell the difference between population I and II (or even III) neutron stars?

This question is related to thoughts I was having about the mass-radius relationship for neutron stars. Is it unique? Is there a single relationship between $P$ and $\rho$ or is there any chance that ...
ProfRob's user avatar
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11 votes
2 answers

What is the frequency of occurrence of stellar classifications off the HR main-sequence?

An alternative version of this question would be: "if was to pick a star from the $10^{11}$ or so in our galaxy at random, what are the probabilities of it being various kinds of star?" (and ...
timday's user avatar
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Population I and II stars

I have been thinking about the formation of the galaxy. I can easily understand that old, low-metallicity stars are in the halo, but I'm missing something when it comes to the disk. If slowly-...
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What is the best evidence/theory about the first generation of stars

In particular, during what range of years after the Big Bang did the stars form? What is the expected range of masses of these stars and what is the expected lifetime before they supernova? I assume ...
FrankH's user avatar
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3 votes
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Code to sample from & integrate light of a cluster?

Are there any publicly available codes to sample from an initial mass function (common ones... Kroupa, Chabrier, Salpeter) to construct a cluster, then use stellar models to generate an integrated ...
keflavich's user avatar
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3 votes
2 answers

Does the recent re-count of stars in elliptical gallaxies affect our understanding of the universal mass balance?

I've seen several popular reports of a new count of low-mass stars in elliptical galaxies (here's one). Edit: Pursuant to several correct comments I've changed the title to agree with the actual ...
dmckee --- ex-moderator kitten's user avatar