Este debate sobre a morte das anãs vermelhas está muito interessante com praticamente três correntes de opinião. Uma que diz que as anãs vermelhas chegam à fase de gigante vermelha e nebulosa planetária acabando depois como anãs brancas. Outra que diz que elas nunca chegam à fase de gigante vermelha, mas que mesmo assim acabam em anãs brancas por contracção gravitacional. E finalmente há mesmo quem diga que elas nunca chegam à fase de anã branca.
Red dwarfs are only massive enough to fuse hydrogen into helium. They will never fuse heavier elements, so the core of helium will simply grow larger as the star gets older. At the end of their lives, a low mass helium core white dwarf will result -the degenerate remains of the red dwarf star's core. It becomes degenerate because no other source of outward pressure is available - the helium is not hot enough to fuse. In single stars, this process takes many tens of billions of years, so the process in still ongoing. In binary stars, transfer of mass between the two stars can speed the evolution -and we do see helium core white dwarf stars in binarysystems.
Red dwarfs are only massive enough to fuse hydrogen into helium. They will never fuse heavier elements, so the core of helium will simply grow larger as the star gets older. At the end of their lives, a low mass helium core white dwarf will result -the degenerate remains of the red dwarf star's core. It becomes degenerate because no other source of outward pressure is available - the helium is not hot enough to fuse. In single stars, this process takes many tens of billions of years, so the process in still ongoing. In binary stars, transfer of mass between the two stars can speed the evolution -and we do see helium core white dwarf stars in binarysystems.
Brown dwarfs remain brown dwarfs forever -- they just slowly cool overtime.
Travis; High Altitude Observatory
Yes, the red dwarfs one day become red giants. Red dwarfs are small cool stars, when they run out of hydrogen in the core they will expand as Sun like stars do and presumably become redder giants (i.e. they will be cooler, redder red giants than Sun like stars). The details of exactly how stars go through the red giant phase does depend on their mass, so there are likely to be some differences between what happens to Sun-like stars and red dwarfs. I don't know what the details are, though I think that it is likely that they would form planetary nebulae. The remaining core will be much less luminous than the bigger stars though and so the nebulae itself would probably be less spectacular in optical light.
Simon Ellingsen : Lecturer in Physics/Radio Astronomy, University of Tasmania
No, red dwarfs do not become white dwarfs. However, red *giants* do. Stars like the Sun (and more massive) will go through the stage of beinga red giant before becoming a white dwarf. Red dwarfs have very very VERY long lifetimes, so in fact the oldest red dwarfs are still red dwarfs. 100 billion year lifetimes are the standard. In the long run, they'll just run out of hydrogen in the core and cool off to become balls of hydrogen and helium that don't emit anything beyond a little infrared radiation.
Brown dwarfs are fairly similar, in some sense, to red dwarfs except that they've never been a star (meaning they never burned hydrogen). So they just get cooler with time.
The friendly wwwastro person; New Mexico University
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