Cosmic Dust Culprit Unmasked

British astronomers have solved one of the darker riddles of the universe - the culprit behind the gargantuan clouds of cosmic dust.

There are around 100 billion galaxies each containing an estimated 100 billion stars in the visible universe. Puzzlingly, almost half of all the visible light from distant stars is blocked by shadowy clouds of dust.

A team led by Loretta Dunne of Cardiff University reports today in Nature that they focused on fine grains of carbon and rock floating in Cassiopeia A, 11,000 light years from Earth, and measured 1,000 times more dust than had been previously detected.

Cassiopeia A is a remnant of a supernova, a star that exploded, showering stellar shrapnel into the cosmos. The conclusion is that cosmic dust is made and then spread by supernovae.

Stars burn hydrogen in enormous thermonuclear reactions, and in the course of doing so forge more complicated atoms, starting with helium. Star factories made all the higher elements in the periodic table, and must also have played a hand in making more complicated molecules found in space, such as water, diamond, amino acids, silicates, formaldehyde and alcohol.

"Effectively, we live on a very large collection of cosmic dust grains," Dr Dunne said. "The question of the origin of cosmic dust is in fact that of the origin of our planets and others."

Cassiopeia A was once a star 30 times the mass of the sun. The dust and debris from the explosion is still travelling outwards at speeds of 10,000km a second. "This is over 1,000 times what has been seen before," said Steve Eales of Cardiff. "Cassiopeia A must have been extremely efficient at creating dust from the elements available."