An X-ray equivalent of the Hubble Space Telescope, the Chandra X-ray observatory, was launched on 23 July. Astronomers look forward to a new view of the violent universe with the highest-quality images ever obtained of X-ray sources.
X-rays are emitted by material with temperatures of more than 1 million degrees, such as hot gas that permeates the space between galaxies, material thrown out into space by stellar explosions and huge superluminal jets ejected by active galaxies.
Astronomers expect to gain new insight into the nature of how spinning-neutron stars work as some pass through an X-ray emitting phase. In particular, magnetars, with their extremely strong magnetic fields, are thought to be at the origin of some gamma-ray bursts.
One of Chandra’s most important results may be the discovery of the origin of the diffuse glow of X-rays that pervades the whole sky the so-called X-ray background. “We think that it is composed of emissions from many distant individual sources of X-rays,” said Martin Ward, director of the X-ray astronomy group at the UK’s University of Leicester. “For the first time Chandra should be able to pinpoint the galaxies and quasars that are responsible for the emission, and we will solve the puzzle of what produces the X-ray background.”
Chandra will also be used to make a new estimate of the age of the universe. Today’s observations suggest that the universe is around 12 billion years old. By measuring the X-ray emission from giant clusters of galaxies, astronomers will make a new estimate using the SunyaevZeldovitch effect. This occurs when hot gas in the clusters scatters the cosmic microwave background radiation.
Chandra is a NASA project, with contributions from the Netherlands, Germany and the UK. The observatory is named after the 1983 Indian Nobel Prize for Physics winner, Subrahmanyan Chandrasekhar, who died in 1995. He was widely known as Chandra, which means “moon” or “luminous” in Sanskrit.
The European Space Agency also plans to launch an X-ray observatory. XMM (CERN Courier July) is scheduled for launch in December. It has a larger collecting area than Chandra better for observing faint sources but lower resolution. X-ray astronomy can only be carried out from space because X-rays are absorbed by the Earth’s atmosphere.
