Quirks & Quarks

How a trick of the light helps scientists spot the same supernova again and again

10 billion years ago, a star exploded. And because of a strange optical phenomenon in which a galaxy can bend and magnify the explosion's light, the Hubble Telescope managed to capture the supernova three separate times.

'Gravitational lensing' means that another viewing will be possible in about 16 years.

To the left is a picture of the galaxy cluster from 2016 in which light from a supernova is seen in three places in the night sky. To the right, is the same area in 2019, where the supernova is now gone. ( S. Rodney (U. of S. Carolina), G. Brammer (Cosmic Dawn Center), J. DePasquale (STScI), P. Laursen (Cosmic Dawn Center))

Recently, astronomers looking out at distant galaxies saw not one, not two, but three supernovas. And because of an ultra rare optical phenomenon, it was in fact the same supernova, repeated three times.

Astronomer Gabe Brammer observed this while looking at a galaxy cluster 4 billion light years away.

"This is kind of a rare part of the universe where there happens to be a big cluster of many hundreds or even thousands of galaxies that are quite distant from us. But those galaxies themselves are magnifying the light of a background source that was discovered a few years ago," Brammer told Quirks & Quarks host Bob McDonald.

This background source is a different galaxy that is 10 billion light years away. While using the Hubble Space Telescope to study this area, Brammer noticed the three images of a supernova. He realized it was actually coming from the same source, but because of a phenomenon called gravitational lensing, the light was being split into multiple images.

This animation demonstrates how light from Supernova Requiem, which exploded about 10 billion years ago, was split into multiple images by a massive foreground cluster of galaxies. (ANIMATION: NASA, ESTEC, STScI, Greg T. Bacon (STScI))

"The light from this very distant source — in this case, the supernova — kind of goes off in all directions and kind of all possible paths. But the lens in this case kind of selected three of those particular paths and redirected them back towards us," said Brammer.

His calculations also suggest that a fourth viewing of the supernova will be possible in about 16 years.

The research was published in the journal Nature Astronomy.

Brammer is an Associate Professor of Astronomy at the Cosmic Dawn Center with the University of Copenhagen. You can listen to his full conversation with Bob McDonald at the link above.

Produced and written by Amanda Buckiewicz


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