Astronomy Picture of the Day |
APOD: 1999 December 19 – Accretion Disk Binary System
Explanation:
Our 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 the case
diagrammed above. Here
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
causing detectable
X-rays,
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.
APOD: 2003 November 10 – An Intermediate Polar Binary System
Explanation:
How can two stars create such a strange and intricate structure?
Most stars are members of
multiple-star systems.
Some stars are members of close
binary systems
where material from one star swirls around the other in an
accretion disk.
Only a handful of stars, however, are members of an
intermediate polar, a system featuring a
white dwarf star with a
magnetic field that significantly pushes out the inner
accretion disk,
only allowing material to fall down its magnetic poles.
Shown above is an artist's depiction of an
intermediate
polar system, also known as a
DQ Hercules system.
The foreground white dwarf is so close to the normal star that it
strips away its outer atmosphere.
As the white dwarf spins, the columns of infalling gas rotate with it.
The name
intermediate polar derives from observations of emitted light
polarized
at a level intermediate to non-disk binary systems known as
polars.
Intermediate polars
are a type of
cataclysmic variable star system.
APOD: 2005 August 30 - Albireo: A Bright and Beautiful Double
Explanation:
Sometimes, even a small telescope can help unlock a hidden beauty of the
heavens.
Such is the case of the bright double star
Albireo.
Seen at even slight magnification,
Albireo unfolds from a bright single point into a beautiful
double star of strikingly different colors.
At 380 light years distant, the two bright stars of
Albireo are comparatively far from each other and
take about 75,000 years to complete a single
orbit.
The brighter yellow star is itself a
binary star system,
but too close together to be resolved even with a telescope.
Albireo, pictured above, is the fifth brightest star system toward the
constellation of the Swan (Cygnus) and easily visible to the unaided eye.
Authors & editors:
Robert Nemiroff
(MTU) &
Jerry Bonnell
(USRA)
NASA Web Site Statements, Warnings, and
Disclaimers
NASA Official: Jay Norris.
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A service of:
EUD at
NASA /
GSFC
& Michigan Tech. U.