Explosive Origin of Super-Bright Supernova Revealed

(CN) – One of the brightest supernovae ever recorded by astronomers gained its notable luminosity when a white dwarf star exploded and sent stellar material smashing into the shell of another star’s explosion, researchers revealed in a study released Thursday.

An artist’s illustration shows what supernova SN2006gy might have looked like if viewed at a close distance. ( NASA / CXC / M.Weiss)

When a star at least five times the mass of our sun burns through its fuel and collapses under gravity’s force, violent shockwaves cause a massive and bright explosion called a supernova.

A supernova can also be produced when white dwarfs – the object that remains after a star the size of our sun runs out of fuel – pull too much matter from nearby stars, creating what’s called a Type Ia explosion.

The superluminous supernova SN 2006gy is one of the brightest ever observed, with a luminosity at least 100 times more powerful than typical supernovae.

Researchers Anders Jerkstrand, Keiichi Maeda, and Koji Kawabata set out to understand how it gained its supreme brightness, according to the study published in Science.

The task seemed daunting since astronomers have struggled to identify the true origin of supernovae energy and the comprehensive analysis of the stars that produce them.

Early observations of SN 2006gy indicated that the stellar explosion was a Type IIn supernova, which is identified by its bright, narrow lines of hydrogen emission. But a year into observations of SN 2006gy, the supernova produced an unusual spectrum inconsistent with Type IIn supernovae, containing emission lines that could not be immediately identified.

After studying various supernova spectral scenarios, researchers concluded that the lines were the result of a large amount of iron in the spectrum. Using spectral and radiation hydrodynamic modeling to produce the scenarios, researchers concluded that only one was consistent with their observations.

SN 2006gy had to have been produced by a normal Type Ia supernova colliding with the dense shell of another stellar explosion, researchers said in the study, adding that the material was likely ejected by a progenitor star about a century before the supernova exploded.

Researchers believe that other superluminous supernovae that bear resemblance to SN 2006gy may be caused by similar astrophysical mechanics, the study said.

Jerkstrand, who is with the Max-Planck-Institute for Astrophysics in Garching, Germany, did not immediately respond to a request for comment.

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