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Star Dust Origins: Case Closed?

Larry O'Hanlon, Discovery News

Photos

Cassiopeia A

Jan. 4, 2008 -- Big things do not always start with little things, at least when it comes to planet-building cosmic dust.

The reversal of the old adage comes from new Spitzer Space Telescope observations of remnants of a supernova explosion called Cassiopeia A, which has left behind what looks like 10,000 Earth masses worth of dust.

The dusty discovery supports the idea that at least some of the universe's first dust -- the most fundamental building blocks of all planets -- was created by the violent deaths of the first generations of giant stars.

"A similar thing happened in the early universe," said astronomer Jeonghee Rho of NASA's Spitzer Science Center at the California Institute of Technology, referring to the explosion of giant stars like Cassiopeia A, which itself blew up only 300 years ago right here in the Milky Way galaxy.

Such explosions of very large stars could possibly account for most of the dust in the universe, Rho said, albeit with a large margin of uncertainty, since accounting for star dust is no easy task. Rho is the lead author of a report about the new Cassiopeia dust measurement, which is slated to appear in the Jan. 20 issue of the Astrophysical Journal.

A speck of star dust, it should be explained, is any collection of matter greater than about 100 molecules in size.

"Dust is an obscuring agent, so it's very important" said researcher Eli Dwek of the Observational Cosmology Lab at NASA's Goddard Space Flight Center. The more you understand dust, the better you can correct for its obscuring effects, he said. And to better understand dust, you need to figure out where it's made.

"Cass-A is a wonderful place to look," said Dwek. "It's relatively young and its [dust] hasn't been mixed with the interstellar medium. It hasn't lost its identity."