Science

Brightest Supernova Ever Found In June 2015

Talk about a cosmic firecracker! The most powerful supernova on record was discovered in the summer of 2015, and this massive explosion that occurred billions of light years away was 600 million times brighter than our own sun.

Astronomers explain that when some stars run out of fuel, or suddenly add new material, they often explode in a gigantic explosion called a supernova. The new supernova appears to be 200 times more powerful than the most commonly found type, and is a member of a class of “super-luminous supernovas.”

When the bright celestial object was first noted back in June of last year, astronomers immediately began to study it. The results of the research are published in the latest edition of Science.

Statement from study authors

“ASASSN-15lh is the most powerful supernova discovered in human history,” lead author Subo Dong, an astronomer at the Kavli Institute for Astronomy and Astrophysics at Peking University, commented. “It provides a great puzzle—it challenges all our previous theories of explosion mechanisms and power sources of superluminous supernovae.”

“The feature which makes it the most unique is just its overall luminosity,” said Ben Shappee of the Carnegie Observatories in California, a researcher who took the first spectrum of the object and a co-author of the study. “It has other features which are part of a rare class called super-luminous Type 1 supernovae, which basically are very luminous and don’t show any hydrogen or helium. So it’s already part of this rare class, and it’s the most extreme example of this rare class,” he told Space.com.

Brightest Supernova Ever Found In June 2015

More on most powerful supernova ever found

Named ASASSN-15lh based the All Sky Automated Survey for SuperNovae (ASAS-SN) telescopic survey that located it, it is thought to be a rare “superluminous supernovae,” which often shine hundreds of times brighter than other types of supernovae. That said, ASASSN-15lh is three times more luminous than the prior brightest record-holder, in fact, it is so bright the researchers say it is close to the limit of what is theoretically possible for stellar explosions.

First spotted ASAS-SN’s twin 14-centimeter telescopes operating in Cerro Tololo, Chile, the object merely appeared as a transient dot of light in an image, and wasn’t noted as anything special. Only after several other telescopes confirmed with more observations of the supernova did it become clear to Dong and colleagues that they were looking at a record-breaking event. The researchers began to seriously consider the object after more data from the 2.5-meter du Pont Telescope in Chile seven days after the initial discovery. “When we saw the spectrum, we were baffled,” Dong said. “It didn’t look like any supernova we had seen.”

Together with Jose Prieto in Chile and Kris Stanek at Ohio State University, it dawned on Dong that the unusual spectrum might match that of another superluminous supernovae in 2010, but only if the new spectrum had been hugely redshifted, that is, stretched out by the expansion of the universe as it traveled billions of light years. Moreover, a high redshift almost certainly means the supernova had taken place at extreme distances, and was therefore extremely bright when it occurred.

The team had to use larger telescopes to get better spectra to confirm their theory. It took more than a week because of bad weather and instrument problems at multiple observatories, but the key data finally came in from the 10-meter South African Large Telescope, confirming that the object was indeed a massive supernova that had occurred around 3.8 billion light-years away.