Stars are astronomical bodies that are (usually) mainly composed of Hydrogen, Helium, and Lithium. They are massive enough that their gravity compresses the matter to the point where nuclear fusion occurs, which creates a lot of heat and tends to make stars output radiation along a blackbody curve. ...

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262 views

Why Does The Moon Apear White/Grayish and The Sun Yellow? [duplicate]

The Sun, as we all know, is white. Because our atmosphere scatters light the sun appears yellow to us hear on earth. So, why isn't the moon also yellow. Doesn't our atmosphere scatter its light. How ...
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0answers
13 views

What is the definition of the “stellar angular diameter” in stellar astronomy?

(Following the definitions here: http://arxiv.org/pdf/astro-ph/0509535.pdf ) What is the "stellar angular diameter", as measured by astronomers specializing in stellar astrophysics? Using the ...
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0answers
18 views

Using stellar spectroscopy to measure stellar parameters, why is it log g?

Stellar spectroscopy can in principle measure the stellar surface gravity, radii, effective temperature, and stellar rotation. Why is it that surface gravity g is ...
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2answers
52 views

Density of the Sun

Being either on the surface or somewhere inside; where is the density of the gases of the Sun equal to the density of the ground we stand on here on earth?
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1answer
34 views

Origin of Stellar Nurseries

What is the mechanism thought to cause huge stellar nurseries to form e.g. eagle nebula?
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1answer
33 views

Best telescope for value per dollar? [closed]

recently I'm thinking of buying a telescope for recreational purposes. I'm looking for telescopes that have the highest performance/cost ratio, and I'm willing to spend around $200 on this. Anyone ...
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1answer
66 views

If the Sun were smaller but had the same surface temperature, would it still have the same luminance?

Let's assume we have two stars that have the same surface temperature but very different size. I understand how luminosity depends on surface area so the two stars will have different luminosity, but ...
2
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2answers
43 views

Are there hypothetical processes which allow the existence of a fission powered star?

I know this is impractical given the rarity of heavy fissile elements in the universe (contrary to the abundance of fusion friendly elements like hydrogen), but is there any process via which a ...
5
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4answers
62 views

Why do stars undergo nuclear fusion?

This might sound silly. But we always talk about nuclear fusion in stars and I have always wondered why this process happens at all. Is it inevitable for fusion to happen at the temperature and ...
1
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3answers
84 views

Can there be eternal stars?

the question is quite straightforward: Can there be stars that shine forever without ever collapsing nor growing? Do we know some really, really old stars? (whatever age that might be) I hope to ...
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0answers
26 views

How do inert helium cores in sub giant stars create a pressure force?

I'm reading about the sub giant branch (SGB) and the evolution to the red giant branch (RGB). On the SGB stars have burned all hydrogen into helium, as a result, they have an inert helium core. The ...
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2answers
33 views

In stellar astrophysics, what is the difference between protostellar disk and circumstellar disk?

I have noticed both the terms "protostellar disk" and "circumstellar disk" in the stellar astrophysics and exoplanet literature. What exactly is the difference?
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0answers
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Why do TiO bands dominate M dwarfs?

I'm new at understanding stellar classification and the spectral classification of stars. What is the exact reason TiO molecules (titanium oxide) dominate the spectrum for M dwarfs? How did this TiO ...
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2answers
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What is the smallest distance possible between two stars?

If two stars of any type were to form near each other, how closely can they form before something prevents them from being two distinct stars?
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0answers
18 views

Books of dynamo theory

I wanted recommendations of dynamo theory pdfs to make a report about magnetic fields of planets and stars with all the math behind it, like vector calculus, Lagrange functions, partial differential ...
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2answers
62 views

Do gamma ray bursts play a role in cosmic evolution?

If gamma ray bursts were to interact with gas clouds in the early universe, might it be a relevant factor in star production?
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1answer
56 views

What is this big, white, dense, circular collection of stars in this picture taken from a Telescope? (See the image)

I was visiting this website- http://crest.iiap.res.in/iaonightcam.html, where there was a picture of the night sky coming live from a Telescope. My question is, why is there so many stars in this ...
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0answers
54 views

Prove that $T_{00}$, $T_{10}$, $T_{01}$, and $T_{11}$ are all $L/(4\pi x^2)$ at $(ct, x, 0, 0)$ for star of constant luminosity $L$

We have a star of constant luminosity $L$. We want to prove that the components $T_{00}$, $T_{10}$, $T_{01}$ and $T_{11}$ are all the same for the event $(ct,x,0,0)$ and they are all $L/(4\pi x^2)$. ...
3
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2answers
63 views

How can we determine the internal structure of a star from distance?

See here for the discussion leading to this question. In essence, I was wondering whether there were methods to differentiate between a star destined to become neutron star and a star destined to ...
0
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1answer
56 views

If both neutron stars and white dwarf stars can have the same mass, what determines what a star of that mass will become when it “dies”?

My understanding is that roughly 1.4 solar masses is the upper limit for white dwarf stars, and that the lower bound for neutron stars is around 1.1 solar masses. Is there any way to tell what a star ...
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1answer
40 views

Would I be able to see light coming towards me before it got to me

If I were in space looking at a star that just started producing light that was two light years away. Would I be able to see the light coming towards me?
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0answers
21 views

Do all stars Turn into Black Holes? [duplicate]

If all stars turn into black Holes one day, in far future, what will happen to Earth if Sun becomes a Black Hole.
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5answers
1k views

Did the Sun form around a solid core?

When Jupiter formed I assume like the other planets it started as tiny clumps of matter that eventually came together, became gravitationally bound and then eventually captured a lot of gas. I've also ...
2
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3answers
600 views

Pure hydrogen star

What is the smallest mass of pure hydrogen that can ignite fusion? That is can population III stars have tiny masses? How would such stars develop? How long would such a star last?
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0answers
27 views

Star collision observation

What would these scenarios look like in real world? I mean, what the result would be?: 2 stars (not necessarily same mass) will collide "side by side", like in, they originally were traveling ...
7
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1answer
199 views

Are the electrons at the centre of the Sun degenerate or not?

Trying to find an answer to this question, I came across two different methods of determining whether electrons at the center of the sun are degenerate or not. The first method, used here, calculates ...
3
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1answer
42 views

Do stars produce spatially coherent light? Why?

If I understand correctly, the existance of astronomical interferometry implies coherence of light produces by stars. The temporal coherence can probably be achieved by wavelength filters. But what ...
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2answers
62 views

Energy of black hole

If a black hole attracts and engulfs light, then why doesn't the energy of the black hole increase to form a star once again? Black holes form when a star burns off its energy and collapses, so it ...
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2answers
98 views

If planet like Jupiter is massive enough to hold hydrogen with its gravity is it bound to become a star?

I have been reading about Jupiter as of late and reason I am asking is if Jupiter has strong enough gravity to pull hydrogen to itself then it should be only matter of time when it will acquire enough ...
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0answers
42 views

Star vs Blackhole - Accretion Disk

Simple question: can we prove that what we call today a "star" is not a accretion disk of a "tiny" black hole that happens to rotate in all the 3 axis?
1
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1answer
85 views

Properties of a star made from water? [closed]

What would the properties of a star formed from a sphere a water/ice be? One large (massive) enough to collapse into an ordinary, mostly plasma star. I understand that it would have particularly high ...
10
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6answers
4k views

What will happen if a ball of ice with the mass of sun is thrown into the sun?

The question is a bit unrealistic with its circumstances but lets assume there is a bucket of ice cooled down to about absolute zero and is about 1000 km away (all around the sun) from sun and moving ...
3
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2answers
89 views

Olbers Paradox Solution

Olbers’ Paradox says that in an infinite universe every line of sight will end on a star. Surface brightness is independent of distance (moving a star further away makes it smaller and reduces its ...
1
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1answer
30 views

What could explain the presence of Promethium in stars? [duplicate]

[This is pretty much a copy and paste job from Technetium question but I wanted to add this one in case there was some other explanation] So, I understand that PM doesn't exist in nature [though, I ...
3
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3answers
78 views

What could explain the presence of Technetium in the spectral lines of stars?

So, I understand that TC doesn't exist in nature [though, I don't know why every reference I see regarding TC says that and then goes on to state that it is found in some stars...] but, if that's the ...
3
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2answers
222 views

What would happen to a star if a Dyson sphere lined with mirrors reflected a significant portion of the stars light back to the star

I have looked for similar questions here on stack exchange. The closest example to this that I found is Could a Dyson sphere destroy a star. That question assumed less than perfect absorption of ...
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0answers
22 views

Emission of sounds from stars [duplicate]

Stars do emit electromagnetic radiation. Is it emit sound - mechanical waves? Sound waves from sun may not travel in space, however, are there any experiment done to detect sounds from sun?
1
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1answer
90 views

Do the arms of a spiral galaxy spin around like a candy bar in long spirals?

Because the arms of a spiral galaxy have a linear center, perhaps they rotate around their center same as a candy bar spiral or a spiral of smoke? Have similar movements within galaxies been measured? ...
0
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1answer
101 views

Metric inside a sphere of uniform density?

Is an exact solution to Einstein's Field Equations known for the interior of a sphere of uniform density (to approximate a star or planet, for example?)
3
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3answers
83 views

Why is the release of energy during the He-flash in stars almost explosive?

Can't really put 2-2 and together as to how having an inert degenerate He core translates to a He-flash. Also, at which points exactly do degeneracy and the He-flash start occurring?
3
votes
3answers
100 views

Is it possible to calculate the radius of star?

Suppose I know the Luminosity $L$, temperature $T$ and Mass $M$ of star. Assuming the star is very heavy so that we can treat it to be radiation-dominated star. This would imply that pressure inside ...
1
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1answer
54 views

Visibility of a super-massive star

I heard that mass and distance are the only deciding criteria for determining the gravitational pull. Keeping the distance constant, if mass would be the only deciding factor for gravitational pull, ...
2
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3answers
211 views

Violation of Pauli exclusion principle

From hyperphysics (emphasis mine): Neutron degeneracy is a stellar application of the Pauli Exclusion Principle, as is electron degeneracy. No two neutrons can occupy identical states, even under ...
6
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2answers
1k views

What would it be like “inside” a star?

This question was triggered by a discussion regarding the computer game Elite: Dangerous, where spaceships routinely operate in close proximity to stars (two or three light seconds away), at which ...
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1answer
55 views

Have scientists always known that the Sun was not a fuel+air system?

Astronomy is far older than nuclear physics. So there was a long time in which fire was a reasonable explanation for the sun burning. Has any scientist figured out the sun cannot possibly be a normal ...
4
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1answer
87 views

How much mass is typically ejected from a supernova?

How much mass is released from a supernova of a 15 solar-mass star? 20? 25? What is the relation between star mass and mass ejected?
26
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4answers
4k views

Why are stars white?

That is may be a easy question, but I am not a professional. The sun is a star and when I look at the sun is usually yellow. Why stars in the night are white? I suppose is for the distance. What is ...
5
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0answers
81 views

Metal-rich star formation

While discussing star formation on cosmological scales with some classmates, we mentioned the breakdown between the different stellar populations via metallicity: Population III: $Z = [{\rm Fe/H}] ...
6
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1answer
373 views

How to tell if a star is in a galaxy?

An astronomer is studying a star that appears to be in a galaxy. How does the astronomer know the star is actually in the galaxy and not just on the same line of sight as the galaxy? I'm guessing ...
1
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0answers
55 views

The standard textbook on supernovae?

This is a straightforward question: What is considered to be the standard treatment of supernovae? Could be a textbook, lecture notes, review article, etc.