Credit: A. Neronov (ISDC, Geneva); E. Churazov (IKI, Moscow); J.-P. Roques (SPI team); F. Lebrun, P. Ubertini (IBIS team); N. Lund (JEM-X team)
The Hole Earth
It's hard to get a clear view of something diffuse, like the cosmic background of high energy radiation. It's hard to know just where it comes from. One simple technique is to look at something at a known distance and see if that thing is in front or behind the background emission. The
moon and the earth are good test objects, though they can be a little tricky to use - they are close to the sun, and sometimes bright in reflected solar emission, which can blind star trackers (needed for accurate pointing). The INTEGRAL gamma-ray observatory recently obtained the image of the earth, shown above, with it's imaging spectrometer, SPI . This image is in the hard X-ray band. In this image the earth is actually not seen - it's the hole in the background emission. This observations clearly shows that the hard X-ray emission originates beyond earth. But not all of it - the INTEGRAL observations suggest that a small part of the emission arises from Earth's aurorae.
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Page Author: Dr. Michael F. Corcoran
Last modified Friday, 20-Apr-2012 15:26:05 EDT