Peering into the heart of a supernova, ALMA maps a huge cloud of dust 

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Thirty years ago, astronomers saw a star exploding in a nearby galaxy. Now, using ALMA, they have imaged the huge cloud of dust that resulted from the explosion. 

When a building collapses, it produces a large dust cloud. That’s because buildings are made of stone. The dust is just pulverized bricks and concrete. 

With stars, it’s different. Stars are not made of stone; they’re made of hot gas. When a star explodes, the gas is blown into space. As a result, it quickly cools down. Atoms of gas then combine into molecules and tiny dust particles. 

In February 1987, astronomers witnessed a huge stellar explosion. It is now known as Supernova 1987A. It occurred in the Large Magellanic Cloud – a small galaxy close to our own Milky Way, at a distance of 163,000 light-years. 

The expanding shell of the explosion – the supernova remnant – has been studied in detail by many different telescopes. But most telescopes can’t look into the very center of the explosion. 

Thanks to its penetrating vision, ALMA could study the innards of the supernova remnant. Moreover, ALMA is sensitive to the millimeter radiation emitted by most molecules. Thus, the 66-dish observatory could study the relatively cool molecular dust cloud that has formed over the past 30 years. 

ALMA detected molecules of silicium monoxide (SiO) and carbon monoxide (CO) – molecules that have also been found in other supernova remnants. The astronomers were able to map the distribution of those molecules in 3D. They also found molecules of HCO+ and sulfur oxide, which had never before been seen in a supernova remnant. 

The new observations help astronomers to better understand dust production in the universe. They also provide a lot of information on supernovas in general. That’s important, because many of the atoms in the world around you were ejected into space by these titanic stellar explosions. 

Who knows, the molecules and dust particles that have been studied by ALMA at the site of Supernova 1987A may one day end up in other planets and alien organisms! 

What? 

Supernova 1987A was the titanic explosion of a very massive star in the Large Magellanic Cloud, a small neighboring galaxy of our own Milky Way. It was discovered on 24 February 1987 by astronomers in Chile. In fact, the explosion happened a long time ago: the light of 

the supernova took some 163,000 years to reach Earth. Over the past 30 years, the supernova has been studied by almost every telescope on the ground and in space, including the Hubble Space Telescope. It is the best studied supernova ever. 

Who? 

The ALMA observations of the dust cloud at the core of the supernova were carried out by a large international group of astronomers, led by F.J. Abellán of the University of Nice (France) and Rémy Indebetouw of the University of Virginia. The results have been published in two scientific articles, one in Astrophysical Journal Letters and one in Monthly Notices of the Royal Astronomical Society.

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