I have heard a lot recently about so-called 'dark stars'; stars that are formed with the help of the gravitational pull of dark matter, or perhaps entirely from self-annihilating Majorana-type dark particles like WIMPs.

I posted a question years ago on Physics SE about why gluons are not expected to annihilate constantly, despite (possibly) being Majorana particles. I also have asked somewhere about why neutrinos, also considered candidate Majoranas, do not seemingly constantly self-annihilate. But I still do not understand why some particle/antiparticles destroy each other upon contact, while others do not.

Gluing and neutrinos do not interact via the electromagnetic force, so some people have said that that is why they do not become photons upon contact but dark matter particles, by their very definition, do not interact electromagnetically either. So I do not understand why WIMPs should be expected to turn into photons when forming a 'dark star'.

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    $\begingroup$ I have edited your question to remove the unnecessary periods/full stop as punctuation. Please time it down a little. $\endgroup$ Commented Aug 27, 2023 at 8:17

1 Answer 1


Gluons actually annihilate, so do neutrinos, just more rarely than Neutralinos.

Neutrinos, Gluons, WIMPS, Majorana particles are always neutral being a Truly Neutral Particle. These Majorana particles don't require electromagnetism, and Maxwell's field, these particles carry a different kind of charge, Lepton Number. C Reversal can also refer to the Lepton number, than electromagnetic charge since Neutrinos are the same lepton family as electrons, and so is it's sparticle. The neutrinos νi are the Dirac particles that have the lepton number L = 1. The lepton number of the antineutrinos ν ¯ i is equal to −1, same applies for it's sparticle, and that's why electromagnetism does not matter in this case.

Gluons are subject to only 1 force: The strong force, and this is the strongest force out there, but it occurs at short distances. Neutrinos, however, interact via two forces: Gravitation and the weak force, so this means they are subject to both Einstien Metric tensor and Yang Mills field.

WIMPS such as Neutralino which are also truely neutral Majorana fermions also interact in a similar manner to neutrinos (Sparticle of Neutrino), except the mass of Neutralino found in dark star is an order of magnitude greater than neutrino, Neutrinos are the lightest particle, and Neutralino are much more massive. So in a Feymann diagram where the distance between the vertices, Neutralinos are more likely to meet and annihilate given that the gravitation force is much more greater than neutrinos.

For example, here is a loop Feymann diagram referring to Gluon annihilation (I picked up this diagram from another answer): Loop Feymann Diagram of Gluon-AntiGluon Anhiliation

Thanks! Hope it is helpful!

  • $\begingroup$ You said, 'WIMPS such as Neutralinos'... But I thought WIMPs are a type of Neutralino? Not the other way around?? $\endgroup$
    – Kurt Hikes
    Commented Aug 29, 2023 at 4:24
  • $\begingroup$ @KurtHikes Neutralinos are weakly interacting massive particles (since they are just the super symmetrical cousin of neutrinos), not the other way around because not all WIMPS are neutralinos. Hope this answers your question! $\endgroup$
    – Arjun
    Commented Aug 29, 2023 at 11:04

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