By Ker Than
New York — Scientists have detected a stellar explosion that is the brightest and most energetic ever recorded—100 times more energetic than typical supernovas—which could provide evidence of a new type of supernova fueled by an antimatter engine.
The “SN 2006gy” explosion, detected in September 2006 using ground-based telescopes and NASA’s Chandra X-ray space observatory, occurred in a the NGC 1260 galaxy 240 million light-years from Earth .
It brightened slowly for 70 days, and at its peak emitted more than 50 billion suns worth of light—shining 10 times brighter than its host galaxy—before dimming slowly. Most supernovas reach peak brightness in days to a few weeks.
“Of all exploding stars ever observed, this was the king,” said Alex Filippenko of the University of California, Berkeley, who led ground-based observations of the supernova at Lick Observatory, Calif., and Keck Observatory in Hawaii.
The finding, presented May 7 at a NASA press conference and detailed in an upcoming issue of The Astrophysical Journal, provides evidence for a fundamentally different type of supernova explosion that only occurs with the universe’s most rare, massive stars .
Supermassive stars are thought to produce so much gamma-ray light at the end of their lives that some of the radiation is converted into matter and antimatter, mostly electrons and positrons. Antimatter particles have the same mass as ordinary matter but opposite atomic properties such as spin and charge. Gamma radiation is the energy that prevents the outer layers of a star from collapsing; once it starts disappearing, the star’s outer layer falls inward, triggering a thermonuclear explosion that destroys the star.
The new findings suggest some of the first stars in the early universe went out in spectacular explosions like SN 2006gy, instead of bypassing the supernova stage and collapsing directly into black holes. “In terms of the effect on the early universe, there’s a huge difference between these two possibilities,” said study leader Nathan Smith, also of UC Berkeley. “One pollutes the galaxy with large quantities of newly made elements, and the other locks them up forever in a black hole.”
Astrophysicists also think the supernova could be a preview of what they will see when a massive star in our own galaxy explodes.
Eta Carinae, the most luminous star in the Milky Way, is located some 7,000 light-years from Earth and seems poised to undergo its own explosion at any moment.
“This could happen tomorrow or it could happen 1,000 years from now,” said Mario Livio of the Space Telescope Science Institute in Baltimore, who was not involved in the research.
Eta Carinae is an unstable star currently radiating about 5 million times more energy than our sun and is undergoing eruptions on its surface that are similar to what scientists think happened on the star that produced SN 2006gy just before it blew.
Despite its relatively close proximity to us, Eta Carinae’s death is not likely to pose any significant threat to life on Earth, scientists say.
“I think we can sleep quietly tonight for Eta Car not extinguishing life on Earth,” Livio said, “but [SN 2006gy] and all the questions it brings about will keep us awake for quite a while.”
