Supernova dust factory spotted by ALMA
Sen—The Atacama Large Millimeter/submillimeter Array (ALMA) telescope has observed, for the first time, the remains of a recent supernova brimming with freshly formed dust.
If enough of this dust makes the transition into interstellar space, it could explain how many galaxies acquired their dusty appearance. Supernovae are thought to be a primary source of the dust in galaxies, especially in the early Universe. Direct evidence of a supernova's dust‐making capabilities has been slim up to now, and could not account for the copious amount of dust detected in young, distant galaxies.
An international team of astronomers used ALMA to observe the glowing remains of Supernova 1987A, in the Large Magellanic Cloud, orbiting the Milky Way about 160,000 light years from Earth.
"We have found a remarkably large dust mass concentrated in the central part of the ejecta from a relatively young and nearby supernova," said Remy Indebetouw, an astronomer at the National Radio Astronomy Observatory (NRAO) and the University of Virginia. "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 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 made with infrared telescopes during the first 500 days after the explosion, detected only a small amount of hot dust.
Remnant of Supernova 1987A seen in different wavelengths. ALMA data (red) shows newly formed dust in the centre of the remnant. Hubble (green) and Chandra (blue) data show the expanding shock wave. Image credit: ALMA (ESO/NAOJ/NRAO)/A. Angelich. Visible light image: the NASA/ESA Hubble Space Telescope. X-Ray image: The NASA Chandra X-Ray Observatory.
With ALMA's unprecedented resolution and sensitivity, the research team was able to image the more abundant cold dust, which glows brightly in millimetre and submillimetre light. The astronomers 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.
Supernovae both create and destroy dust grains. As the shockwave from the initial explosion radiates out into space, it produces bright glowing rings of material. After hitting this envelope of gas, a portion of the explosion rebounds back towards the centre of the remnant.
"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." said Indebetouw. If a good fraction survives and makes it into interstellar space, it could account for the copious dust astronomers detect in the early Universe.
Keele University’s Dr Jacco van Loon commented, "Since we first detected cold dust in the direction of SN1987A with telescopes in space and on the Atacama Altiplano we have been using the most powerful observing facilities on Earth to zoom in on the exact location of this dust and separate its radiation from that of other sources of radio emission. It took the many dishes of the new ALMA observatory, that joined together to mimic a very large telescope, to finally confirm what astronomers hoped to find."