Astronomers say observation of an exploding supernova has helped them understand the origins of interstellar dust that fills the universe between stars.
An unusually bright supernova observed in 2010 in a nearby galaxy -- the death throes of a giant star 40 times as massive as our sun -- allowed them to observe a cosmic dust "factory" in action, they say.
The researchers used a ground-based telescope instrument in Chile to make 10 observations of the supernova SN2010jl over a period of two and a half years, yielding a timeline of how a supernova creates dust, the size of the particles and their material composition.
Whilte astronomers have long assumed that cosmic dust is the residue of supernova explosions, the mystery has been how the delicate grains condense out of the stellar material and manage to survive the violent shock waves that accompany the immense blasts.
"The problem has been that even though dust grains composed of heavy elements would form in supernovae, the supernova explosion is so violent that the grains of dust may not survive," study co-investigator Jens Hjorth at the University of Copenhagen says.
Writing in the journal Nature, the astronomers explain that dust formation begins quickly when the supernova begins to explode and is ongoing for a long time following the initial eruption.
A short time before the initial explosion, the dying star throws off gases rich with carbon, helium and hydrogen that form a dense shell surrounding the star.
"When the star explodes, the shockwave hits the dense gas cloud like a brick wall," study lead author Christa Gall, of Aarhus University in Denmark, says. "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 those densities and temperature the elements in the gas can come together, or nucleate, to form solid particles, Gall says.
"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."
The opportunity to observe an emerging supernova from its initial explosion through its subsequent creation of remnants of dust is providing insights into how the cosmic dust factories operate, the researchers say.
And it's that dust that eventually creates everything from rocky worlds like the Earth to the complex chemistry that can eventually become the life that lives on it, they add.
