Credit:European Space Agency/EPIC team
The bright star Castor is a well known to observers; Castor and its "twin"
Pollux mark the constellation of Gemini. Many people would be surprised to
learn that the optical star Castor is in fact composed of 6 stars. This
sextuplet consists of a pair of
A-type stars, Castor AB, orbiting each other with a period of 467
years. Around each of these A-type stars orbits another star, an invisible
dwarf. Just south of this pair of A-type stars is the star YY Gem, another
binary composed of 2
M dwarfs which dance around each other every 19 hours. X-ray
astronomers have known for some time that YY Gem and at least one star in
the Castor AB system are X-ray sources. A new observation with the EPIC camera on
XMM-Newton shows that all 3 binaries
are sources of X-rays from gas at temperatures of millions of degrees.
Throughout the 25-hour observation of the sextuplet, the EPIC images reveal
that all three X-ray sources are variable, indicating giant releases of
energy that can evolve in a few minutes or over several hours. But the
frequency of the flaring on Castor is quite surprising. At no period during
XMM-Newton's observation was the emission constant, perhaps indicating that
almost all of the observed X-ray radiation stems from giant eruptions.
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Page Author: Dr. Michael F.
Last modified June 30, 2000