Early Galaxies’ Thick Dust Linked to Supernovas

A cold-seeking camera attached to the James Clerk Maxwell telescope in Hawaii has solved the mystery behind the excessive dust previously detected in the early universe.

British astronomers using the Submillimeter Common-User Bolometer Array, or SCUBA, a powerful camera that can detect dust grains at temperatures more than 450 degrees below zero, discovered that massive supernovas actually spew a thousand times more dust into their surrounding galaxies than astronomers had originally thought.

“We were quite surprised and excited,” said Loretta Dunne , an astronomer at Britain’s Cardiff University and lead author of the study published Thursday in the journal Nature. “Its very important because there has been this big puzzle about the origins of all this dust.”

Astronomers know that when stars like our sun die, they blow enormous quantities of material out into space. The stellar remnants eventually cool and condense into wisps of carbon and silicates as fine as cigarette smoke. However, because stars like our sun live for several billion years, and because the distant, dusty galaxies that SCUBA found are about 1 billion years old, these stars could not be responsible for the excessive dust.

The next most logical dust-producing suspects are stars that are far more massive than our sun and have much shorter life spans -- on the order of millions, rather than billions, of years, Dunne said. But these stars are fairly rare and were thought to produce far too little dust until Dunne and her colleagues pointed SCUBA at the remains of one such star 11,000 light years away -- supernova remnant Cassiopeia A.

“It’s a very funny thing to think that dust matters, but dust matters significantly,” said Doug Johnstone, a star-formation astronomer for the National Research Council in Canada.

“Dust is really important in allowing stars to form,” Johnstone said, “and in producing structures like the Earth and, ultimately, life.”