Chandra X-Ray Observatory

Chandra X-Ray Observatory, or CXO, one of the “Great Observatories” of the US National Aeronautics and Space Administration (NASA), designed to study the X-ray part of the electromagnetic spectrum. Named after the distinguished Indian-American astrophysicist Subrahmanyan Chandrasekhar, it was launched by NASA on July 23, 1999. CXO was then injected into a high Earth orbit with a period of 63.5 hr, which allows for long, unbroken observations of X-ray sources (compared to the more usual 100 min low Earth orbit, of which typically only about 45 per cent is useable). The observatory, which can produce X-ray images up to 10 times sharper than those obtained by any previous X-ray telescope, also has the capability to undertake (together with the XMM observatory of the European Space Agency), for the first time on faint X-ray sources, high-resolution X-ray spectroscopy. This allows CXO to determine both the composition and dynamics of the X-ray emitting gas (which must be at temperatures of millions of degrees), and CXO has already provided astronomers with a wealth of remarkable data as well as spectacular pictures. It has been able to account for the previously puzzling glow of diffuse X-rays that pervade the universe (the so-called “X-ray background”) by resolving this glow into a huge number of faint, individual X-ray sources, most of them galaxies probably containing accreting, massive black holes, some of these being the farthest objects so far detected. CXO has also made studies of the black hole at the centre of the neighbouring Andromeda galaxy, and produced images of cannibalistic galaxies, X-ray jets emanating from the supermassive black holes at the centres of active galaxies (such as M87) and quasars, and glowing planetary nebulae. See also X-ray Astronomy.