Tangentially related but I can’t seem to find the answers and I have a couple questions that perhaps someone can answer:

1. Do stars actually generate muons directly? From what I understand the muons on Earth are a result of cosmic rays colliding wtih particles in the atmosphere.
2. If they do, how far do they travel before decaying? Even if they travel at relativistic speeds, they have a mean lifetime of 2.2 ns, so the math seems to say they don’t travel very far at all on average.
3. Either way, are there any other sources of muons in the universe? I’m curious what the muon density distribution in the universe would look like.