UK scientists have used the ALMA telescope to help capture the remains of a recent supernova - or exploding star – that is brimming with freshly formed dust 160,000 light years from Earth. Supernovae are thought to produce a large amount of the dust within galaxies, especially in the early Universe, but direct evidence of their ability to create dust has been limited - until now. The results appear in Astrophysical Journal Letters.
An international team of scientists including two from each of University College London and Keele University have used the European Southern Observatory (ESO)’s Atacama Large Millimeter/submillimeter Array (ALMA) telescope to observe the glowing remains of Supernova 1987A (link opens in a new window)  (link opens in a new window). The relatively young supernova is in the Large Magellanic Cloud, a dwarf galaxy orbiting the Milky Way about 160,000 light-years from Earth. SN 1987A is the closest observed supernova explosion since Johannes Kepler's observation of a supernova inside the Milky Way in 1604.
"Really early galaxies are incredibly dusty and this dust plays a major role in the evolution of galaxies,"
said Mikako Matsuura of University College London (UCL). "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."
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 with infrared telescopes, made during the first 500 days after the explosion, detected only a small amount of hot dust.
This artist's illustration of Supernova 1987A reveals the cold, inner regions of the exploded star's remnants (in red) where tremendous amounts of dust were detected and imaged by ALMA. This inner region is contrasted with the outer shell (lacy white and blue circles), where the blast wave from the supernova is colliding with the envelope of gas ejected from the star prior to its powerful detonation.
(Credit: ALMA (ESO/NAOJ/NRAO)/Alexandra Angelich (NRAO/AUI/NSF))
With ALMA's unprecedented resolution and sensitivity, the research team was able to image the far 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.
Dr Jacco van Loon from the Lennard-Jones Laboratories, Keele University, said:
"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."
Remy Indebetouw, an astronomer at the National Radio Astronomy Observatory (NRAO) and the University of Virginia, both in Charlottesville, USA, added:
“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."
Jacco van Loon said the discovery is very exciting for everyone – not just astronomers: "While supernovae signal the explosive destruction of stars, for the rest of the Universe they are a source of new stuff and energy; our lives would be very different without the chemical elements that were synthesized in supernovae throughout the history of the Universe. Grains are incredibly difficult to make in the vast emptiness of space - much different from our daily experience! If supernovae indeed make lots of them then this would have had very important and positive consequences for the eventual formation of the Sun and Earth as well."
Masa Lakicevic a PhD student at Keele University and Professor Michael J Barlow from UCL are the other two UK authors on the paper in Astrophysical Journal Letters which is entitled, ‘Dust Production and Particle Acceleration in Supernova 1987A Revealed with ALMA’.
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