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I can't imagine that the concentration of matter ejected, which diffuses impressively, would have been so concentrated so far away. Supernovae shockwaves are th

I can't imagine that the concentration of matter ejected, which diffuses impressively, would have been so concentrated so far away. Supernovae shockwaves are thought to be a candidate for touching of the process of dust cloud collapse and stellar formation, but an old star is usually a really dense core and a very wispy atmosphere, relatively speaking. Maybe a shockwave could set off a nova event, or the addition of matter could trigger a collapse, but I'm not sure how it could jumpstart nuclear fusion again.

pixl97 10y ago
Do we have any idea what occurs if a young star and an old star merge? Of course my first thought on that line of thinking is that would cause some type of explosion or ejecta that would be noticeable, but maybe not.
- S_Daedalus 10y ago
  I think that might be one of those seemingly straightforward questions that's actually very nuanced, because I suspect that the combined masses of the two stars will have a lot to say about the outcome. For a couple of Solar mass stars, I would expect... a big explosion. I can't imagine it really happening though, except in a one-in-a-<insert -illion of choice> "head-on" collision. In that case, whether it blew apart and re-settled into a star, or a nebula, or... just blew apart, would be a function of mass and momentum. In the case of slowly decaying orbits, one star usually ends up stripping most of the atmosphere from its partner, before the core eventually passes its Roche limit, breaks apart, and is accreted. In that case you get a series of Novas (not to be confused with supernovas), and a somewhat larger star when all is finally said and done. Lots of debris, occasionally very bright. It's hard to imagine a situation in which two stars "merge" without a slow process of cannibalization. Compact collapsed bodies like white dwarves, neutron stars and the rest definitely do merge, but they're so much denser than a "living" star.

pixl97 10y ago

Do we have any idea what occurs if a young star and an old star merge? Of course my first thought on that line of thinking is that would cause some type of explosion or ejecta that would be noticeable, but maybe not.

S_Daedalus 10y ago
I think that might be one of those seemingly straightforward questions that's actually very nuanced, because I suspect that the combined masses of the two stars will have a lot to say about the outcome. For a couple of Solar mass stars, I would expect... a big explosion. I can't imagine it really happening though, except in a one-in-a-<insert -illion of choice> "head-on" collision. In that case, whether it blew apart and re-settled into a star, or a nebula, or... just blew apart, would be a function of mass and momentum. In the case of slowly decaying orbits, one star usually ends up stripping most of the atmosphere from its partner, before the core eventually passes its Roche limit, breaks apart, and is accreted. In that case you get a series of Novas (not to be confused with supernovas), and a somewhat larger star when all is finally said and done. Lots of debris, occasionally very bright. It's hard to imagine a situation in which two stars "merge" without a slow process of cannibalization. Compact collapsed bodies like white dwarves, neutron stars and the rest definitely do merge, but they're so much denser than a "living" star.