Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have directly imaged the huge amounts of freshly formed dust in the remnant of Supernova 1987A.
Supernova 1987A (SN 1987A) is a stellar explosion that occurred from a star about 20 times the mass of the Sun. This supernova was first observed on February 23, 1987 in a nearby galaxy, the Large Magellanic Cloud, some 164,000 light-years away.
SN 1987A is the closest supernova to be witnessed with the naked eye from our planet in the past four centuries, and has been providing scientists with good opportunities to study physical processes of an exploding star.
Scientists predicted that as the gas cooled after the explosion, large amounts of dust would form as atoms of oxygen, carbon, and silicon bonded together in the cold central regions of the remnant.
However, earlier observations of SN 1987A with infrared telescopes, made during the first 500 days after the explosion, detected only a small amount of hot dust.
With ALMA, Dr Remy Indebetouw from the National Radio Astronomy Observatory and the University of Virginia with colleagues were able to image the far more abundant cold dust, which glows brightly in millimeter and submillimeter light. They estimate that the remnant now contains about 25 percent the mass of the Sun in newly formed dust. They also found that significant amounts of carbon monoxide and silicon monoxide have formed.
“SN 1987A is a special place since it hasn’t mixed with the surrounding environment, so what we see there was made there. 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,” said Dr Indebetouw, who is the first author of a paper accepted for publication in the Astrophysical Journal Letters (arXiv.org).
Supernovae, however, can both create and destroy dust grains. As the shockwave from the initial explosion radiated out into space, it produced bright glowing rings of material, as seen in earlier observations with Hubble. After hitting this envelope of gas, which was sloughed off by the progenitor red giant star as it neared the end of its life, a portion of this powerful explosion rebounded back towards the center of the remnant.
“At some point, this rebound shockwave will slam into these billowing clumps of freshly minted dust,” Dr Indebetouw explained.
“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 a good fraction survives and makes it into interstellar space, it could account for the copious dust astronomers detect in the early Universe.
“Really early galaxies are incredibly dusty and this dust plays a major role in the evolution of galaxies,” said second author Dr Mikako Matsuura from University College London.
“Today we know dust can be created in several ways, but in the early Universe most of it must have come from supernovae. We finally have direct evidence to support that theory.”
Indebetouw R et al. 2013. Dust Production and Particle Acceleration in Supernova 1987A Revealed with ALMA. ApJL, accepted for publication; arXiv: 1312.4086