Supernova dust factory seen at last; may explain early galaxy formation

Using a powerful radio telescope, scientists have spotted an enormous cloud of dust billowing in the center of a supernova - finally.

The discovery, announced at the American Astronomical Society, helps to confirm what scientists have long thought - that massive supernova explosions could have provided the dust found in the first galaxies.


Early galaxies were dusty places, but where did that dust come from when the universe was still so new?

Astronomers hypothesized that supernovae - the end-of-life explosions of stars at least eight times the size of our sun - may have been the source of that ancient, primordial dust.


There was just one problem with the hypothesis - whenever astronomers looked at a supernova, they never found enough dust to confirm that it was possible.

"We looked at dozens of supernova, and the amount of dust we found always fell short of what we predicted," said Remy Indebetouw, an astronomer with the National Radio Astronomy Observatory and the University of Virginia. "So then we started to wonder: Can they do it? Can supernova make enough dust to explain everything that happens in the first galaxies of the universe?"

In a new study accepted for publication by Astrophysical Journal Letters, Indebetouw and his colleagues show that they can.

Using the powerful ALMA telescope in the Chilean desert, the researchers were able to detect huge amounts of dust in the center of a supernova called 1987a. This supernova, first seen in 1987, lies in the Large Magellanic Cloud, a dwarf galaxy that orbits the Milky Way at a distance of 168,000 light-years from Earth.


"This was the first time that we were really able to image at high resolution dust that unambiguously formed out of the core of the star before it exploded," Indebetouw said.

The first image in the photo gallery above is a composite of supernova 1987a taken with three telescopes. The red stuff in the center of the image is cool dust that was detected by ALMA. It is equivalent to one-quarter the mass of our sun.

In the next image, you'll see an artist's illustration showing the red cloud of dust in the middle of a knotty blue, white and purple ring. That ring is where the energy of the supernova is colliding with the envelope of gas ejected from the star before it exploded.

Indebetouw said his dust discovery would not have been possible without ALMA, which is 10 times more sensitive than previous telescopes.

A few years ago, he was part of a team that imaged 1987a using the less powerful Herschel telescope. While they were able to determine there was a lot of dust in the vicinity of the supernova, they couldn't tell whether it was inside or outside the ring. If it was outside the ring, it could be dust that was already there.

But the new data make it clear that the dust is located firmly inside the ring. It was a gratifying discovery, Indebetouw said.

"When we saw it we were like, 'Awesome. Our ideas about supernova and the early universe might actually work.' "

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