I believe there was an article not too long ago on space.com about two stars that are rotating around each other and will eventually collide? My question is, what will happen?
My guess is that they would shuck off a good portion of their outer gasses, throwing it into a ring that would gradually be pulled back. Eventually they would settle back down into a larger, hotter star with a very unstable magnetic field. The star's effective lifespan would probably be significantly shortened by this whole process as well. A lot of this depends on the types of stars involved. A white dwarf could literally continue to orbit within the thin outer gasses of a red supergiant... at least until friction forces it down into the gravity well.
i am just hopeing that something totally new happens . i could love to see some new things happing in space .
I'd agree with Clockwood: mutual tidal effects will tear huge masses of gas of both stars long before their atmospheres combine. The pair will be wrapped in a shared nebula which may follow their orbital plane, dependent on whether the orbits coincide with their separate axial rotations. The ejected material might even accrete to form new planets, or a new low-mass star if there's enough of it. In the scenario of a white dwarf being engulfed by its expanding supergiant companion: wouldn't the diffuse atmospheric gas be drawn down and concentrated on the dwarf's surface, rather than robbing it of speed as it passed through? Before too long, the dwarf would accumulate enough new mass to cause a nova explosion - or even a type I supernova, which would clearly destroy both stars.
Another possibility is that the two dwarfs would combine to form a neutron star (if the mass left behind exceeds the Chandrasekhar limit). If a white dwarf is too massive, it overcomes the degeneracy pressure of its own protons and electrons, forcing them together to become a superdense mass of neutrons.
Or two neutron stars could merge to form a black hole, if the combined mass is more than about 3.2 Solar masses. At the lower mass end, two brown dwarfs could collide to form a new red dwarf: sort of a second chance for failed stars. In the distant cosmic future, long after normal star formation has ceased and the galaxy has become dark and degenerate, a few dozen red dwarfs formed in this fashion may be the only stars shining...
I think that stars seldom, if ever, actually collide. A collison requires that their velocity closely approximate a straight line path toward eachother. If their path deviates from a straight line by even a small amount, they tend to orbit in an ellipse or fly away from eachother on parabolic-like paths. Close encounters might result in one star forming an accretion disk about the other and slowly being consumed. This is more likely than an actual collision.
If they approach within a few dozen astronomical units of each other, however (a hair's breadth in interstellar terms) their mutual gravitation will come into play. Even if two passing stars do not make physical contact at their first encounter, they may engage in a long parabolic orbit as you suggested; eventually they will swing about and come together again, perhaps colliding after a few passes.
Starthane Xyzth: I do not think it is a simple as you describe. Two extremely rigid objects are not likely to collide unless they start out on a path approximating a collision course. Even small deviations from the collision course result in both being accelerated to high velocities. When they get near to each other, they pass at high speed and either go into an elliptical orbit or get flung apart never to approach each other again. For a more realistic situation (stars which are not not rigid objects), tidal forces start separating matter from each star before they can collide. If one is much more massive that the other, the mass of the smaller star forms an accretion disk spiralling into the large star. It is my guess that nearly equal mass stars become a rotating gaseous cloud which collapses into a single star.
I have read descriptions of colliding galaxies. It is my understanding that there are few stellar collisions when this occurs.
Not surprising. The individual stars within galaxies are so widely separated that they would be like two swarms of midgies passing through each other, or two salvos of buckshot. Even with billions of stars on both sides, direct hits are unlikely.
