Topic: CH Cyg: A Close-up View of Codependent Stellar Living

[sam]

CH Cyg is a binary star system containing a white dwarf that feeds from the wind of a red giant star. The material from the wind forms a hot accretion disk around the white dwarf before crashing onto the star. CH Cyg is one of only a few hundred symbiotic systems known, and one of the closest to the Earth. Symbiotic systems are fascinating objects, where the components are codependent and influence each other's structure, daily life, and evolution. They are likely progenitors of bipolar planetary nebulas and they could make up some of the systems that later explode as Type Ia supernovas, spectacular explosions visible across cosmological distances.

http://chandra.harvard.edu/photo/2010/chcyg/

[Clive]

What a delightful and rare star system.  White dwarfs are basically tiny dead stars which are far too faint to be seen in amateur telescopes.  Our Sun will eventually become a white dwarf and will remain in that state for up to a trillion years before turning into an invisible black dwarf.  What is so fascinating about *this* particular system (CH Cygni) is that it is being rejuvenated by matter streaming from the red giant star and might even gain enough mass to turn back into a "proper" star again thus giving it an extended lease of life.  It will of course eventually end up as a white dwarf again.