X-Ray Pleiades
The Pleiades star cluster is one of the
jewels of the northern sky.
To the unaided eye it appears as
a lovely and tantalizing grouping of stars in
the constellation of Taurus,
while telescopic views reveal cluster stars
surrounded by delicate blue wisps of dust-reflected starlight.
To the X-ray telescopes
on board the orbiting
ROSAT observatory,
the cluster also presents an impressive,
but slightly altered, appearance.
This false color image was produced from ROSAT observations
by translating different
X-ray energy bands to visual colors - the lowest energies are shown
in red, medium in green, and highest energies in blue.
(The green boxes mark the position of the
seven brightest visual stars.)
The Pleiades stars seen in X-rays have extremely hot, tenuous
outer atmospheres called coronas and
the range of colors corresponds to different
coronal temperatures.