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I am layman in particle physics. I saw this question about gravitation affecting neutrinos. There is link to an article, but it is too difficult for me. Is it known if and where can neutrinos orbit heavy objects, say centre of galaxy, is their trajectory stable?

John Rennie
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weatherman
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Neutrinos have mass and so they are affected by gravity (indeed, even if they were massless, they would still be affected by gravity, just as photons are). However, the mass of a neutrino is very very small, so neutrinos emitted by the the nuclear fusion processes inside stars (and in even more extreme events such as supernovae) have speeds that are very close to the speed of light - they are relativistic particles. Because they travel at speeds so close to the speed of light, it is very difficult to directly measure the speed of a neutrino and this is an area of ongoing research - see this Wikipedia article

To go into a closed orbit around a galaxy, a star or even a black hole, a neutrino would have to lose energy and slow down. But because they are not affected by the electromagnetic force or the strong nuclear force, neutrinos hardly ever interact with other particles, so a relativistic neutrino is very unlikely to lose enough energy to ever go into a closed orbit.

gandalf61
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