6
Complications in Binary Systems
•Can move mass between stars
•1st (massive) star becomes red giant
•Its envelope transferred to other star
•Hot (white dwarf) core exposed
•
•2nd star becomes red giant
•Its envelope transferred to white dwarf
–Accretion disk around white dwarf
•Angular momentum doesn’t let material fall directly to white dwarf surface
–Recurrent nova explosions
•White dwarf hot enough for fusion, but no Hydrogen fuel
•New fuel comes in from companion
•Occasionally ignites explosively,
 blowing away remaining fuel