Scientists reveal origin of cosmic dust

AARHUS, Denmark, July 10 (UPI) -- For a while now scientists have known about cosmic dust -- that it exists and that it builds planets. They also had hypothesized it was formed by stellar explosions. (Where else would it have come from?)

But astronomers and physicists have never quite understood how fine grains of cosmic dust formed from stellar material, and more puzzlingly, how something so delicate could could survive the violent shock waves of the supernova combustions.

Now, however, they've gathered some important clues.

"When the star explodes, the shockwave hits the dense gas cloud like a brick wall," explained Christa Gall, an astronomer at Aarhus University, in Denmark, and author of a new study on the phenomenon. "It is all in gas form and incredibly hot, but when the eruption hits the 'wall' the gas gets compressed and cools down to about 2,000 degrees."

"At this temperature and density elements can nucleate and form solid particles," Gall continued. "We measured dust grains as large as around one micron (a thousandth of a millimeter), which is large for cosmic dust grains. They are so large that they can survive their onward journey out into the galaxy."

Gall and her fellow researchers were able to gather these new clues and arrive at a fuller understanding of the genesis of cosmic dust by watching a supernova explosion up close.

In 2010, the eruption of the extremely bright supernova SN2010jl -- located in the galaxy UGC 5189A, some 160 million light-years from Earth -- served as an ideal venue for monitoring the formation of dust. Using the European Space Observatory's Very Large Telescope, located in northern Chile, Gall her team of astronomers continued to monitor the aftermath of the explosion for two years. Their observations offered new insights into how dust survives and coalesces in the wake of a violent supernova.

"Our research casts new light on this -- both on how dust is formed and how it survives the shockwaves," Gall said of her study's findings, which were published in the latest edition of Nature.