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December 26, 1995
Accretion Disk Binary System
HST Artist's Visualization
Sun is unusual in that it is alone - most
stars occur in multiple or
binary systems. In a binary system, the
higher mass star will evolve faster and will eventually
become a compact object - either a
white dwarf star, a
neutron star, or
black hole. When the lower mass star later
evolves into an expansion phase, it may be so close to the compact star
that its outer atmosphere actually falls onto the compact star. Such is
gas from a blue giant star is
shown being stripped away into an accretion disk around its compact binary
companion. Gas in the accretion disk swirls around, heats up, and
eventually falls onto the compact star. Extreme conditions frequently
occur on the surface of the compact star as gas falls in, many times
gamma-rays, or even
cataclysmic novae explosions. Studying the extreme conditions in these
systems tells us about the inner properties of ordinary matter around us.
Tomorrow's picture: Nova Cygni 1992
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