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Space Observatories

Space telescopes have proliferated in recent years. Many of the new “observatories” operate at definite parts of the electromagnetic spectrum. XMM-Newton (10 December 1999) is the largest satellite ever launched by the European Space Agency; it is over 9 metres (30 feet) long and weighs 4 tons. It comprises two payload modules connected by a long carbon-fibre tube, which forms the optical telescope bench. X-ray telescopes, three of which are carried in XMM-Newton, are quite unlike optical telescopes, but are remarkably effective; for example Newton has discovered a vast ball of hot gas, 3,000,000 light years across, streaking through a galaxy cluster known as Abell 3866, in the far southern constellations of Horologium (the Clock) and Reticulum (the Net). One member of the research team, Professor Mark Henriksen of Baltimore, said that “as the gas ball races through the cluster, individual galaxies tear portions of it away to stimulate future star growth”, and he likened it to “a giant comet streaking through the heavens”; but a comet is icy, while the temperature of the gas ball is 55,555,538°C (100 million °F) – so hot that it cannot be seen in the optical range, but is striking afterglows at X-ray wavelength.