Questions tagged [fusion]

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Why does nuclear fusion generate heat?

I understand that nuclear fusion generates energy in the form of gamma-rays (as in the pp chain), but how does that translate into heat in the star's core? Or is the heat just generated by ...
Astrovis's user avatar
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2 votes
1 answer
204 views

Pure Lithium Star

Suppose by some miracle a large molecular cloud of pure lithium assembled itself in space, then gravitationally collapsed. What would the result look like? Would it be a star of some sort (fusing the ...
volcanrb's user avatar
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8 votes
1 answer
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Within the Milky Way, how much helium is made each second?

The Milky Way has 100-400 billion stars. Our sun is a fairly average example, and it converts 3.7× 10^38 protons to helium each second, through two different fusion pathways. I would like to know the ...
WaveInPlace's user avatar
0 votes
2 answers
86 views

Does most of the Sun's energy and light come from its black-body temperature, due to its massive size alone? Constant crashing of particles?

Stars have to be a certain size to initiate fusion to begin with, correct? Isn't this why brown dwarfs are considered 'failed stars'? But wouldn't the Sun (and other stars with sufficient mass, like ...
Kurt Hikes's user avatar
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2 votes
1 answer
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Is there a way to compare input and output energy of solar fusion to the input and output energy of man made fusion?

The Livermore fusion experiment was said to be 2 megajoules of energy in and 3 megajoules of energy out. However upon closer inspection the facility used 300 megajoules of energy. So man made uses 300 ...
Sedumjoy's user avatar
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22 votes
2 answers
5k views

Do stars become more metal-rich as they evolve?

Since we determine the metallicity of a star ([Fe/H] or Z) from surface emission, does this change as it ages? For instance, can a young star with a measured [Fe/H] of -0.02 have a higher value when ...
Jack R. Woods's user avatar
1 vote
1 answer
142 views

Bremsstrahlung's role in the sun

Due to nuclear fusion that produces gamma rays which goes through compton scattering, in the end, on the surface, visible, infrared light ends up as before then, gamma rays lost energy and became x-...
Giorgi Lagidze's user avatar
4 votes
1 answer
77 views

How does carbon end up in the remnants

We know that one way carbon ends up in the interstellar medium which by the way is one or the heavy elements that help form the planet. But we also know that in the core, carbons fuse with another ...
Giorgi Lagidze's user avatar
4 votes
2 answers
192 views

Do brown dwarf 'stars' fuse simple hydrogen (p-p reaction) at all?

I sometimes read that only deuterium-deuterium fusion can occur in brown dwarfs... And maybe deuterium-proton fusion? To He-3? In order to overcome Coulombic repulsion and, occasionally, fuse, protons ...
Kurt Hikes's user avatar
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6 votes
3 answers
307 views

In layman's terms, why does the cold C-N-O process end in Carbon?

I read up a little bit on fusion in stars, layman's articles only and the P-P chain makes hydrogen or Alpha particles. (error removed on triple-alpha), then the C-N-O process adds hydrogen to the ...
userLTK's user avatar
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2 votes
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How much of the hydrogen in our sun will never participate in fusion? What about larger stars? [duplicate]

From what I gather, only red dwarf stars are fully convective, and will use up pretty much all of their hydrogen.... Is there a chart or list somewhere that shows the percentage of hydrogen that is ...
Kurt Hikes's user avatar
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1 vote
0 answers
61 views

Weak force beta + and - decays [closed]

What is the role of the weak nuclear force in nuclear fusion, changing a proton to a neutron to produce deuterium and in neutron stars when a fundamental particle, the lepton electron, is fused in to ...
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8 votes
1 answer
1k views

What is it like to see a brown dwarf turn into a star?

Brown dwarfs/failed stars can actually become stars, if they exceed a mass limit of about 80 Jupiter masses. This is when the internal pressure and temperature at the core become high enough to ...
Alastor's user avatar
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3 votes
1 answer
269 views

What are the temperature and pressure requirements to fuse hydrogen and deuterium in Jupiter?

I've done some Google research to find out. All found sources approached the question from a mass viewpoint. That is, Jupiter has to be about 70 - 80 times more massive to be a red dwarf (through ...
William's user avatar
  • 657
5 votes
4 answers
301 views

If two fast asteroids collided, would the temperature and pressure be high enough to cause nuclear fusion?

Some near earth objects travel with speeds of dozens of kilometers per second. Would a head-on collision between two of them create suitable conditions for nuclear fusion?
2080's user avatar
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17 votes
1 answer
647 views

Is stellar ignition all-or-nothing?

The boundary between brown dwarfs and stars is around 80 Jupiter masses. Only stars generate a self-sustaining hydrogen fusion, although brown dwarfs sometimes fuse lithium and deuterium. Is hydrogen ...
Kevin Kostlan's user avatar
3 votes
1 answer
611 views

Why do stars usually stop fusion at iron, even though nickel-62 has the highest binding energy per nucleon?

We know that iron is often regarded as 'nuclear ash' because of its inability to fuse with other atoms, as it has a high binding energy per nucleon. However I found that Nickel-62, grabs the title of ...
Kshitij Kumar's user avatar