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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2answers
56 views

How do we know singularities/black holes actually bend time?

Recently I read up on some articles about singularities / black holes, how they form and how they affect their surroundings. Just to clarify, I am no physicist and I found those articles on the ...
1
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0answers
14 views

Number of stars with apparent flux

The stars in our Galaxy have luminosities ranging from $L_{\text{min}}$ to $L_{\text{max}}$. Suppose that the number of stars per unit volume with luminosities in the range of $L$, $L+dL$ is $n(L)dL$. ...
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0answers
30 views

Influence of matter of a star on masses of neutrinos

It is well known that if neutrinos has masses then from Dirac equation it follows that they propagate (in vacuum) as a eigenstates of mass (not as eigenstates of interaction). It's wave function is of ...
1
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1answer
51 views

Resource: Star map which show current actual positions versus current observable positions?

Light travelling from stars and galaxies takes some time to reach us here on Earth - when we observe stars or galaxies in the night sky, we see their positions as they were when the light left on its ...
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5answers
3k views

Can elements heavier than Iron be present in a star's core?

My understanding is that elements heavier than Iron and Nickel are not formed in a star but, can heavy elements such as lead and others be present/found in a star's core ? I ask because the following ...
23
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5answers
4k views

Why is the Sun called an “average star”?

This is a statement (presumably in mass, longevity, energy output) many people that I've met have heard in school, and it is known in pop culture. However, according to Wikipedia, about 75% of the ...
8
votes
4answers
240 views

Why are some stars very large (i.e., $r \geq 1000 \ R_{\odot}$) but not super massive?

Background While I was in graduate school, I put together some cartoon-like comparisons of multiple stars to show the order of magnitude differences in radii. At the time, VY Canis Majoris was the ...
14
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2answers
2k views

What is the farthest planetary body or star system object we have observed using visual light?

What is the farthest object which we can get a direct Detailed visual image of using visible light which appears more than just a dot and falls into one of the following categories: Planet Satellite ...
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2answers
61 views

Is it possible that there are stars working on fission?

Most/all stars are getting their energy from fusion of small atoms like our sun. But is it possible according to the laws of physics that there are stars getting their energy from fission fe with ...
3
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0answers
63 views

Mass of star from Lane-Emden equation

Suppose we have equation of state $p=K\rho^{1+\frac{1}{n}},$ where $\gamma=1+\frac{1}{n}$ for some star. Then by standard calculations we obtain equation for enthalpy $h$: $$\Delta h+4\pi G\left(\frac{...
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2answers
50 views

Does the solar wind correspond to a net electrical current?

The solar wind is a stream of ions emitted from the sun. Are there more positive than negative charges released? That is, is there any imbalance in the charge emitted from the sun in the solar wind?
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1answer
41 views

Identify binary stars in nbody simulation

I'm doing a nbody simulation, and I'm interested in the formation of binary systems in the temporal evolution. I can identify them by eye, but I don't know an algoritmic criteria that can say me if ...
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1answer
26 views

Stellar classifiaction and metals

I have recently started to study astronomy and there is a thing with stellar classifications I can't get my head around: The colder the star the more absorption lines from metals are present in its ...
1
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2answers
113 views

Why doesn't sunlight flicker like candle or flame torch?

Why sunlight appears constant and stable like sun is a bulb? If the surface of the sun and processes going in it are not completely uniform why don't we notice any flickering or non- uniformity in ...
9
votes
2answers
790 views

Do stars remain electrically neutral? [duplicate]

How electrically neutral do stars remain through their lifetime? As an example, I could imagine processes such as coronal mass ejections leaving the Sun in a slightly charged state. Are there such ...
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1answer
66 views

How does the energy of a supernova compare to that of its parent star?

How can the energy produced in a supernova be quantified? And, if the energy of the supernova is not equal to the energy of the parent star, how do we account for this difference?
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2answers
44 views

Distances between stars and their sizes

At the begining I wish to apologise for naive question, but one thing puzzles me. Let's say we observe two stars that have average brightness. One can easily see that they are not points, but those ...
1
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1answer
72 views

Does a singularity appear the instant a black hole is formed? [duplicate]

Imagine a very heavy (tens of solar masses) star in its final moments before collapsing to form a black hole. The gravitational force exerted by the weight of the star overcomes the neutron degeneracy ...
1
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1answer
51 views

Are there star systems orbited by stars? [closed]

I never really heard about such occurencies and now asked my self if this could be possible. So could there be systems with a star (or black hole) that is so heavy that other less heavy stars are ...
21
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2answers
3k views

Why is the cut off mass for massive stars 8 solar masses? Why can't it be 10-11 solar masses or so?

I know that stars having a mass greater than or equal to 8 solar masses are termed "massive stars". But why is the cut-off 8 solar masses?
3
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2answers
486 views

How can a low-mass star increase its mass to 1.4 Msun?

In my astronomy class I learned that a only low-mass stars (< 0.5 Msun) will contract, and then become degenerate, until it is a white dwarf. However, we also learned about the Chandrasekhar limit, ...
4
votes
2answers
164 views

Why aren't the hottest stars mostly invisible due to radiating mostly in ultra-violet? [duplicate]

The hottest stars have surface temperatures in the range of 40,000K. Wolfram Alpha says that such a star acting as a black body should radiate almost no energy in the visible spectrum. Why then do ...
5
votes
2answers
842 views

How to calculate the force of gravity that wants to collapse a star?

In astrophysics, the pressure created by the outflow of energy from the interior of the star counteracts the force of gravity that wants to collapse the star. If I want to calculate this force for a ...
2
votes
1answer
53 views

How much energy does proton - carbon 12 fusion produce?

Page 25 of this document from the California Institute of Technology says that proton-carbon 12 fusion releases 7.54 MeV, while Wikipedia says it releases 1.95 MeV. Which one is correct?
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5answers
108 views

Could it be possible for man to create a star? [closed]

If it were possible for us to create a star or a new sun, how could it be done, or how would it have to be done?
16
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8answers
4k views

How do stars from far away affect Earth?

I know that we obviously get light (or we wouldn't be able to see them), but are there any other ways that they affect Earth and maybe just our solar system in general?
1
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1answer
50 views

Has a stellar blackhole more mass than previously?

What is the coefficient of mass gained/lost by a star in its first phase transitioning into a blackhole. Does the blackhole have more or less mass than the star it was made from? Thank you Regards
0
votes
3answers
122 views

If our eyes see at the speed of light, how do we know about the current states of stars and galaxies far away?

As you guys know that we see at the speed of light, it means that we see the past of stars and galaxies. So say a star went supernova right now, how are we able to know current state of that star that ...
0
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0answers
63 views

Would a grid of $10^{57}$ hydrogen atoms collapse?

Assume we have a gridded cube of $10^{57}$ hydrogen atoms, with all atoms 1mm apart from other atoms. This 'cube cloud' is in an area of space that would otherwise be at zero g, were it not for the ...
3
votes
1answer
43 views

Classification of binary star system

I'm not an astrophysicist, but I'm studying a binary star system and I need some clarification about star classification. The spectrum seems to be F8V-like. The absolute magnitude is between 12 and ...
1
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0answers
27 views

Dust mass-loss rate from a massive star given a set of parameters?

I've been looking for examples at how mass-loss rates are determined. I'm studying a circumstellar dust shell ejected from a Wolf-Rayet star. I have some parameters like, expansion velocity of the ...
2
votes
1answer
98 views

Observation of a dying star

Looking far away mean looking back in time. Stars evolve and then after long time they die. Some of them evolve in supernova. Other than this case, when looking at the sky with telescopes, are there ...
4
votes
2answers
109 views

How do we know what happens to stars during their life cycle?

It is common knowledge than Sun-sized stars will eventually become red giants, and later they will get gradually smaller again until they cool down into a brown dwarf, and that bigger stars can ...
2
votes
2answers
130 views

Why does a light wave fade as it travels through space?

It stands to reason: if it didn't, the entire sky would be covered with stars shining blindingly day and night. But what causes a light wave (or an electromagnetic wave) to fade if there are no ...
3
votes
2answers
104 views

Is sun a black body? [duplicate]

My teacher told me that sun is a black body but after reading at various sites whre they say that sun is not a black body but has black body radiations because it cannot absorb all radiations.
1
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2answers
95 views

We say Light is Red-Shifted or Blue-shifted from faraway stars and galaxies [closed]

We say Light is Red-Shifted or Blue-shifted from faraway stars and galaxies. Can we find out the distance at which it changed its frequency. So in another solar system, it might seem to be Green ...
4
votes
1answer
265 views

Why do astronomers call all elements heavier than helium “metals”?

I understand that a scientific term need not be constrained by its etymology. But is there some significant reason why astronomers choose to call all elements heavier than helium "metals"? Are ...
1
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1answer
68 views

Eccentric binary black holes

Comparable-mass binary black hole inspirals and mergers are expected to be an important source of gravitational wave signals for current and future ground-based detectors. It is generally expected ...
0
votes
1answer
50 views

Why only binary star system produce ripples in space-time (gravitational waves)?

I saw a statement being made in a video, but it didn't explain why. It originally said, "stars orbiting each other does not create gravitational waves, binary system of two massive stars or black hole ...
4
votes
1answer
162 views

Why do neutron stars have solid crusts?

A long time ago I read that neutron stars have a solid crusts that are several orders of magnitude harder/stronger than alloys here on the Earth. So how is this possible ? A neutron star has a ...
1
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2answers
57 views

Sound speed vs Speed of sound

Are 'sound speed' and 'speed of sound' the same thing? If not, what is the difference? If they are, could you clarify how the speed of sound applies in the below description of gaseous clouds? ...
1
vote
1answer
58 views

What percentage of the energy in a dust cloud must be lost before it can collapse into a star?

With reference to this previous question about how dust clouds can collapse to form stars: How is hydrostatic pressure overcome when a star is formed? The answer given is that they must radiate away ...
17
votes
4answers
2k views

How is hydrostatic pressure overcome when a star is formed?

If stars are formed by the collapse of dust clouds under gravity, how is the pressure of the dust cloud overcome? As more material gathers together, gravity will increase, but pressure will also ...
2
votes
2answers
136 views

Why does the core of a low mass star contract after reaching electron degeneracy?

I am learning about the lives and deaths of stars with a solar mass of 0.4-2. What I understand is that once the star stops hydrogen fusion after using up all its hydrogen, the star leaves the main ...
2
votes
2answers
90 views

Why can I always see a star? [duplicate]

Light moves along straight lines... Got it. So if the light from that faraway star is traveling in a straight line, and that beam is, considering the distaces involved, at best one or two photons "...
4
votes
0answers
53 views

Which is the mechanism through which dying stars shed their outer atmosphere and leave behind their core? [closed]

I was looking into neutron star creation and I read that when a star dies, it expells its outer atmosphere and leaves behind a really small really dense nucleus (a white dwarf if the first star was a ...
1
vote
0answers
59 views

If entropy is positive, then why do stars form from nebulae?

Sorry if I have so many misconceptions with this questions, but I guess that's the point of asking questions. If entropy, the measure of disorder, is always positive, then how come a star could form ...
1
vote
2answers
140 views

Good books or resources for Stellar Astrophysics at graduate level?

I wanted to know if there is a well established resource in the field of Stellar Astrophysics which is not very outdated. I have seen plenty of books at my university library but I do not know if ...
1
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2answers
283 views

How long would it take to see the nearest star die?

If you were in the general proximity to the nearest star to Earth (besides the Sun) and you saw it turn to a neutron star or black hole at the very end of it's star cycle, how much longer would it ...
1
vote
1answer
95 views

How to calculate how much energy a body gets from a star?

Okay, so I could swear that I've seen an equation before for this (which I believe involved the Stephen-Boltzmann constant.) But now that I actually need it, much like my reading glasses I can't seem ...