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and Cosmology

Extragalactic Astronomy and Cosmology: An Introduction

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1.3 The Tools of Extragalactic Astronomy<br />

33<br />

Fig. 1.33. The left image shows the Compton Gamma Ray Observatory<br />

(CGRO) mounted on the Space Shuttle manipulator<br />

arm. This NASA satellite carried out observations between<br />

1991 <strong>and</strong> 2000. It was finally shut down after a gyroscope<br />

failed, <strong>and</strong> it burned up in the Earth’s atmosphere in a controlled<br />

re-entry. ESA’s Integral observatory, in operation since<br />

2002, is shown on the right<br />

discovered many AGNs at very high energies above<br />

20 MeV, which hints at extreme processes taking place<br />

in these objects.<br />

The successor of the CGRO, the Integral satellite,<br />

was put into orbit as an ESA mission by a Russian Proton<br />

rocket at the end of 2002. At a weight of two tons, it is the<br />

heaviest ESA satellite that has been launched thus far. It<br />

is primarily observing at energies of 15 keV to 10 MeV<br />

in the gamma range, but has additional instruments for<br />

observation in the optical <strong>and</strong> X-ray regimes.

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