ROSAT Lockman Hole
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. Corcoran
Last modified December 17, 2001