16 July 1998
Astronomers Reveal Hidden Universe
Deep in the outer reaches of the Universe there exists a population of strange, dusty galaxies radiating about the same amount of stellar energy as the entire optical Universe put together. So say an international team of astronomers, who report their findings in the July 16 issue of Nature.
The discovery, which is supported by a parallel British study appearing in the same issue of Nature, has been described as "a true revolution in submillimetre astronomy" - not least because the results suggest that much of the star formation taking place in the distant Universe may be hidden to visual observation, even from powerful observatories like the Hubble Space Telescope.
According to the astronomers, dust in galaxies absorbs starlight emitted at visible wavelengths by hot young stars, then reradiates it at much longer wavelengths. In extremely dusty galaxies, most visible light is reradiated into the far-infrared. For galaxies at large distances, this light is even further "redshifted" by the expansion of the Universe to wavelengths slightly less than a millimetre. By contrast, the wavelength of visible light is about a thousandth of a millimetre.
"The recent submillimetre observations have opened an exciting new era in cosmological exploration comparable to that which occurred with the restoration of image quality with the Hubble Space Telescope," says Richard Ellis, director of the Institute of Astronomy at the University of Cambridge, UK.
"The pioneering deep exposures conducted by groups in Hawaii, the UK, and Canada have shown the importance of studying galaxies at large look-back times at wavelengths other than simply the traditional optical and infrared regions. Understanding this new population is essential in order to obtain a comprehensive picture of cosmic galaxy formation."
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