Herschel looks back in time to see today's stars bursting into life

An international team of astronomers have presented the first conclusive evidence for a dramatic surge in star birth in a recently discovered population of massive galaxies in the early Universe.

The scientists used the European Space Agency’s Herschel Space Observatory, an infrared telescope with a mirror 3.5 m in diameter, launched in 2009. They studied the distant objects in detail with the Spectral and Photometric Imaging Receiver (SPIRE) camera, obtaining solid evidence that the galaxies are forming stars at a tremendous rate and have large reservoirs of gas that will power the star formation for hundreds of millions of years.

Dr Scott Chapman from the Institute of Astronomy at the University of Cambridge, presents the new results in a paper in a special edition of the journal Monthly Notices of the Royal Astronomical Society focusing on results from Herschel.

"These Herschel-SPIRE measurements have revealed that a population of galaxies is hotter than expected, due to forming stars far more rapidly than we previously believed," he said.

The key to the new results is the recent discovery of a new type of extremely luminous galaxy in the early Universe. These galaxies are very faint in visible light, as the newly-formed stars are still cocooned in the clouds of of gas and dust within which they were born. This cosmic dust, which sits at around -232 C, is much brighter at the longer, far infrared wavelengths observed by the Herschel satellite.

A related type of galaxy was first found in 1997 (but not well understood until 2003) using the "SCUBA" camera attached to the James Clerk Maxwell Telescope on Hawaii, which detects radiation emitted at even longer sub-millimetre wavelengths. But these distant "sub-millimetre galaxies" were thought to only represent half the picture of star formation in the early Universe. Since SCUBA preferentially detects colder objects, it was suggested that similar galaxies with slightly warmer temperatures could exist but have gone largely unnoticed.

Dr. Chapman and others measured their distances using the Keck optical telescope on Hawaii and the Plateau de Bure sub-millimetre observatory in France, but were unable to show that they were in the throes of rapid star formation.