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Universität zu Köln
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Mathematisch-Naturwissenschaftliche Fakultät
Fachgruppe Physik

I. Physikalisches Institut

Worldwide observing campaign lead by work group of Prof. Eckart

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Sagittarius AAt the heart of the Milky Way lies a supermassive black hole, called 'Sagittarius A*'. It contains 3.7 million times as much mass as our Sun. A few times per day, Sagittarius A* shows sudden bursts of radiation - termed 'flares' - that can be detected with X-ray observatories (like the American satellite 'Chandra' or the European 'XMM' observatory) and with radio and optical telescopes. These flares are related to the black hole guzzling gas and dust from its environment. However, the exact cause of the flares remains enigmatic. Astrophysicists believe that they can learn a great deal about black holes and Einstein's theory of relativity from a study of these phenomena. In order to understand the flares of Sagittarius A* it is necessary to examine their behavior in as many regions of the electromagnetic spectrum as possible, from X-rays to radio waves. The effort for preparing such experiments is very high because observing time has to be proposed for at many observatories across the world. Additionally, all these observations have to take place at the same time. The astrophysicists of the group around Prof. Andreas Eckart from the University of Cologne, in collaboration with scientists from the USA, have been successful in setting up such a campaign. In May they will observe the black hole for 10 days with telescopes around the world. Participating observatories are the Very Large Telescope of the European Southern Observatory (ESO) and the Gemini South telescope in Chile, the radio telescope in Effelsberg, Germany, the Plateau de Bure Interferometer in France, the IRAM30m telescope on the Pico Veleta near Granada in Spain, the new CARMA radio interferometer and the Very Long Baseline Array (VLBA) in the USA, and the ATCAradio interfermeter in Australia. By combining radio telescopes across three continents, it will be possible to observe the black hole for 24 hours a day. Scientists from the University of Cologne will be present at all these telescopes in the time from 14 to 24 May 2007. Galactic Center science at the I. Physikalisches Institut of the University of Cologne

(May 7, 2007, rs)