Astronomers trace the mysterious origins of supernova a hundred times brighter than a regular one

New evidence suggests that the explosion — dubbed SN 2006gy — may have resulted from a collision between a pair of white dwarfs and a relatively massive star


                            Astronomers trace the mysterious origins of supernova a hundred times brighter than a regular one
An artist's illustration of supernova SN 2006gy (NASA)

The year 2006 featured a monstrous explosion, a hundred times brighter and more energetic than a typical supernova, emerging about 240 million light years away. This unusual explosion has baffled scientists until now, as they were unsure of its origins.

New evidence suggests that the explosion — dubbed SN 2006gy  — may have resulted from a collision between a pair of white dwarfs and a relatively massive star, making it unique. This outburst shows a behavior typical of type la supernovae, say scientists.

"It has been postulated that superluminous supernova like SN 2006gy come from a peculiar (unknown) type of supernova explosion — the death of a massive star. This study, however, suggests that at least SN 2006gy is from a usual type la explosion at its heart," co-author Dr. Keiichi Maeda, associate professor at Kyoto University, Japan, tells MEA WorldWide (MEAWW).

The culprits behind type la supernovae explosion are white dwarfs. These explosions see two stars or a binary star system participating: one star steals enough material from its companion. This goes on until the star collapses and blows up into a supernova.

Optical (left) and X-ray (right) images of SN 2006gy. The dimmer source at lower-left is the nucleus of the host galaxy. The brighter source at the upper-right is the stellar explosion. The supernova was as bright as the entire core of a galaxy (NASA)

During this detonation, massive amounts of chemical elements present in a star are released, including those essential for making planets and life. Identifying these elements could help astronomers understand the origins of SN 2006gy.

To detect them, Maeda and his colleagues observed the light coming out after the explosion. This light gave out spectral lines, which act like signatures of atoms, elements or molecules. As each atom has a signature of its own, studying them helps astronomers identify these elements.

However, the fingerprint of SN 2006gy was bizarre: "They were enigmatic and unidentified — we did not understand which elements make these lines," explains Maeda. After deep inspection, Maeda and colleagues saw that the "mystery element" was neutral iron. This points to its origin as supernova type la, he adds.

Normally, supernova la originates when a pair of a white dwarf smashes against a low-mass star or between a pair of two white dwarfs. But SN 2006gy was a lot more dramatic: instead of a low-mass star, the explosion involved a relatively massive star, explains Maeda.

This explosion is different from a normal supernova on another count — its environment. "The environment around the explosion was peculiar too, containing materials — which could be remnants of the massive star companion. Most of supernova Ia explode within a clean environment, with little material surrounding the exploding star," says Maeda.

This environment around SN 2006gy makes it special, without which, adds Maeda, SN 2006gy would have been a normal supernova explosion. The same process may have driven other superluminous explosions, similar to SN 2006gy, says the study.

"Of course, this is a single example, and this means this is our real start to understand superluminous supernova explosions in general. They are bright and thus are promising light probes toward the distant Universe," adds Maeda.

The study has been published in Science.

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