The birth of new stars has been captured on film. The heat emitted by a galaxy some 20 million light years distant has been captured in the first pictures taken by the European Space Agency's orbiting Infra-red Solar Observatory (ISO).
The galaxy is similar to our own - it is a spiral like the Milky Way. The white spots in the pictures are hot gas and dust coming together to create new stars.
The birth pangs of stars have hitherto been concealed from human sight, because the heat-radiation (infra-red "light") is absorbed by the Earth's atmosphere. In November 1995, the European Space Agency launched its infra-red telescope into orbit with the express purpose of capturing such events for detailed analysis by astronomers.
The results will cast light on the evolution of our own solar system. Astronomers believe that the Sun and the planets condensed out of a disc of hot gas and dust some 5 billion years ago.
The data from ISO has been eagerly awaited by the astronomers. There are billions of galaxies in the universe and most of them are powerful emitters at infra-red wavelengths. More than nine-tenths of the energy output of many galaxies is in the infra-red. This "bias" is, astronomers believe, caused by a large burst of star formation, sometimes because of two galaxies colliding.
The ISO is so sensitive that it will perform the equivalent of detecting from the centre of London the heat radiated by a snowman in Cambridge. But this exquisite sensitivity is bought at a price: the satellite has to be cooled by evaporating liquid helium from a tank at -271C (just above absolute zero) to avoid the detector being swamped by heat from the satellite that carries it.
Even accidental exposure to the heat emitted by the Moon could cause the telescope to overheat and so irreparably damage the detectors.
Astronomers' appetites for infra-red observations were whetted some 12 years ago by the results from an Anglo-Dutch satellite known as IRAS. It identified more than 25,000 sources of infra-red radiation in the sky. But compared with ISO it could only take fairly crude pictures of the universe.Reuse content