January 6, 2014
Supernovas Could Be Galactic Dust Factories, According To New Observations
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Lee Rannals for redOrbit.com - Your Universe OnlineA new image of a recent supernova could offer up insight to scientists about how galaxies became so dusty. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope have observed the remains of supernova 1987A located in the Large Magellanic Cloud about 168,000 light-years from Earth. This is the closest observed supernova explosion since Johannes Kepler's observation of a supernova inside the Milky Way in 1604.
The new observations, reported in the Astrophysical Journal Letters, show the remains of a supernova, complete with freshly formed dust. If this dust is able to make it out into interstellar space, then it may explain how galaxies become dusty.
"We have found a remarkably large dust mass concentrated in the central part of the ejecta from a relatively young and nearby supernova," Remy Indebetouw, an astronomer with the National Radio Astronomy Observatory (NRAO) and the University of Virginia, both in Charlottesville, said in a statement. "This is the first time we've been able to really image where the dust has formed, which is important in understanding the evolution of galaxies."
Astronomers believe that gas cooling after the explosion formed large amounts of molecules and dust as atoms of oxygen, carbon and silicon. Earlier observations of the supernova made within the first 500 days after explosion detected only a small amount of hot dust.
The team believes the remnant supernova now contains about 25 percent of the mass of our Sun in newly formed dust. They found that significant amounts of carbon monoxide and silicon monoxide have formed as well.
"1987A is a special place since it hasn't mixed with the surrounding environment, so what we see there was made there," said Indebetouw. "The new ALMA results, which are the first of their kind, reveal a supernova remnant chock full of material that simply did not exist a few decades ago."
When a supernova explodes, a shockwave is sent out into space, producing bright glowing rings of material. However, when this shockwave reaches an envelope of gas, a portion of it rebounds back towards the center of the remnant.
"At some point, this rebound shockwave will slam into these billowing clumps of freshly minted dust," said Indebetouw. "It's likely that some fraction of the dust will be blasted apart at that point. It's hard to predict exactly how much – maybe only a little, possibly a half or two thirds."
If some of the dust is able to reach interstellar space then it could account for the dust that astronomers detect in the early Universe. Mikako Matsuura with the University College London says the dust from early galaxies plays a major role in the evolution of galaxies.
"Today we know dust can be created in several ways, but in the early Universe most of it must have come from supernovas. We finally have direct evidence to support that theory,” Matsuura said in a statement.