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31 votes
Accepted

Can there be planets, stars and galaxies made of dark matter or antimatter?

Dark matter galaxies are possible but very speculative. On a theoretical level, they are hard to form because dark matter interacts only gravitationally (see Anders Sandberg's answer), which makes it ...
Allure's user avatar
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28 votes

Can there be planets, stars and galaxies made of dark matter or antimatter?

Probably not. Dark matter should really be called "transparent matter" since it does not interact with light. This has an important consequence: it is hard for dark matter - whatever it is - ...
Anders Sandberg's user avatar
22 votes

What observations show that galaxies are made of matter instead of anti-matter?

When you say anti-matter, I assume you mean the opposite of what our Galaxy is made of. Obviously you can label what we are made of as matter or anti-matter as you wish, the point is that the universe ...
ProfRob's user avatar
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12 votes

antimatter annihilation in stars

The proton-proton chain ultimately converts four protons into one helium nucleus. The charge of the 4 protons was balanced by 4 electrons, but helium contains 2 protons (and 2 neutrons), so it only ...
PM 2Ring's user avatar
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11 votes

Is Anti-Dark Matter a thing?

Yes, it is a thing. Weakly Interacting Massive Particles (aka WIMPS) are thought to come in matter and anti-matter forms and have a self-annihilation cross-section in order to produce the "correct" ...
ProfRob's user avatar
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7 votes
Accepted

Scenarios: Abusing a black hole

Black holes are not "made of matter". They are better described as structures of gravity/warped spacetime. However, they do grow when absorbing things with positive mass-energy. Antimatter still has ...
Anders Sandberg's user avatar
5 votes

antimatter annihilation in stars

They are not replaced. Fusion in ordinary stars means actually many processes, neutrinos are involved most commonly in these: $p + p \rightarrow D + \nu_e + e^+$ $T \rightarrow He_3 + \nu_e + e^+$ ...
peterh's user avatar
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5 votes

Can there be planets, stars and galaxies made of dark matter or antimatter?

Gravitational lensing observations suggest that there is a large mass of dark matter on either side of the bullet cluster, which is actually one of the major pieces of evidence that dark matter does ...
Hearth's user avatar
  • 151
3 votes

Symmetry in Hawking radiation?

This assumes that when a pair particle-antiparticle is created, a bias towards antiparticles being captured and particles escaping must exist. No such assumption or bias exists. As far as we know ...
StephenG - Help Ukraine's user avatar
3 votes
Accepted

Anti matter in Jupiter magnetic field?

Yes it is. See this 2012 blog post by Paul Gilster: https://www.centauri-dreams.org/2012/05/17/powering-up-the-antimatter-engine/ It says things like this: Antimatter in space is an idea that ...
John Duffield's user avatar
3 votes

The Matter Anti Matter Asymmetry

Energy can indeed transform into matter - for example pair production; but this creates equal amounts of matter and anti-matter.
ProfRob's user avatar
  • 156k
3 votes

How does Hawking Radiation work exactly?

... but how does the other know how to take energy from the black hole? In order to understand this, you need to be familiar with the essence of this picture$^1$ including negative energy states ...
Ad Astra's user avatar
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3 votes
Accepted

Could the newly discovered glow in the solar system be antimatter?

No, this visible glow cannot be due to matter-antimatter annihilation. As Peter Erwin mentions, electron-positron annihilation produces gamma-ray photons, (mostly) with the energy of 511 keV. Proton-...
PM 2Ring's user avatar
  • 15k
2 votes

What observations show that galaxies are made of matter instead of anti-matter?

A recent article, Constraints on the antistar fraction in the Solar System neighborhood from the 10-year Fermi Large Area Telescope gamma-ray source catalog, suggests that there might well be stars ...
David Hammen's user avatar
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1 vote

What observations show that galaxies are made of matter instead of anti-matter?

You basically answered your question with your sub-questions. Detection would be through the process of annihilation - either for individual atoms, or for a star hitting an anti-star with an ...
AnoE's user avatar
  • 165
1 vote

What are the sources of antimatter particles in the magnetosphere?

Matter and antimatter particles are always produced as a pair. This particle physics' process is called pair production. If antimatter is detectable, it means that the antiparticle of a matter-...
B--rian's user avatar
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1 vote

The Matter Anti Matter Asymmetry

Many products are created by Matter and Anti Matter collision but is dependent on what matter antimatter that is annihilating. Example electron and a positron annihilate create 2 photons. Proton-anti-...
Dean Pitts's user avatar
1 vote

antimatter annihilation in stars

I'm stealing a bit from other answers, just to clarify the point here. What follows is not exactly how it all happens, but should clarify how electrons and positrons are balanced. The key to the ...
tuomas's user avatar
  • 1,837
1 vote

Conversion of matter into antimatter

This is from my general relativity course from many years ago. I don't think there have been any discoveries since that would invalidate it. There is this thing called the no hair theorem for ...
Kenneth R Cosner's user avatar

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