Credit: The ROSAT Mission and Max-Planck-Institut für extraterrestrische Physik
Looking through a Hole in the Sky
Trying to observe the X-ray Universe beyond our Galaxy from our particular
vantage point in the Milky Way is like looking at the sky on a cloudy day.
That's because large clouds of gas and dust in the Milky Way block our view
of the external X-ray emission in most directions. But there are certain
directions in the sky, the clouds part. One such direction is known as the
"Lockman Hole" - this is the the place in the Galaxy where the clouds are
thinnest and where most of the X-ray emission from the rest of the Universe
can shine through. The image above is an X-ray image of
the Lockman Hole, obtained by the ROSAT X-ray
observatory. The white lines are contours showing the thickness of the
Milky Way's clouds in the Lockman Hole. The X-ray emission and the cloud
thickness are clearly anti-correlated - where the clouds are thick the X-ray
emission is weak while where the clouds are thin, the X-ray emission is
stronger. This shows that most of the X-ray background in this direction
originates in the space beyond the Milky Way.
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Page Author: Dr. Michael F.
Last modified December 17, 2001