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Cold Dust At The Heart Of TheUniverse

June 28, 1996

The Universe contains vast quantities of very cold dust and gas; from the relatively dense regions where young stars are born to the most distant galaxies, still in the process of forming after the Big Bang. The new SCUBA instrument, conceived, designed and built at the Royal Observatory, Edinburgh and installed on the James Clerk Maxwell Telescope in Hawaii, will make important breakthroughs in the study of these challenging and exciting phenomena.

The spaces between the stars are very cold, where the interstellar dust and gas is typically at -260 degrees Celsius. Yet it is in these very dense dust clouds that stars are born. Just as a heated poker cools and glows redder until eventually an infrared camera is required to see its emission, so astronomers need detectors sensitive to even longer wavelengths, between 0.3 and 1.0 mm, to detect the feeble radiation from this very cold dust in the Universe. This is the sub-millimetre domain, sandwiched between the radio and infrared.

This wavelength range is also of critical importance in the study of phenomena at the largest scales in the Universe. Primordial galaxies, still forming after the Big Bang, are the most distant objects we can see in the Universe. Because of the expansion of the Universe these objects appear to be speeding away from us at a high velocity, with the result that the radiation is shifted to longer wavelengths - right into the submillimetre region.

Similarly the Cosmic Background Radiation, the glow left over from the Big Bang which uniformly fills all space, is now known to contain tiny fluctuations which correspond to the early formation of the largest-scale structures in the Universe. The peak of this radiation again falls close to one millimetre.

A giant leap forward in capabilities at these wavelengths is about to be made by SCUBA (Submillimetre Common-user Bolometer Array). SCUBA is a camera with many detectors and so able to take a picture, whereas previously the sky had to be scanned with a single detector to build up an image. It also gains greatly in intrinsic sensitivity by cooling these detectors to within a tenth of a degree of absolute zero, the coldest temperature possible. All in all a 5,000-fold increase in power will be achieved.

The successful development of the advanced cryogenics, electronics and mechanical engineering in SCUBA, has been a major challenge for the Royal Observatory, Edinburgh (ROE), in collaboration with Queen Mary and Westfield College in London, and has been funded by the James Clerk Maxwell Telescope (JCMT) Development Fund, to which the UK Particle Physics and Astronomy Research Council (PPARC) is the main contributor, together with its partners Canada and the Netherlands.

AlphaGalileo Foundation