Biggest Supernova Discovered
Gigantic Stellar Explosion Reveals New Type of Supernova
A star 150 times more massive than our Sun has exploded in the galaxy NGC 1260, 240 million light-years away in the direction of the constellation Perseus. Despite that tremendous distance, this supernova has become the brightest and longest-lasting stellar explosion. Not only is it the biggest of its kind, it is currently the only of its kind. Its massive destruction taught scientists that this was a new kind of supernova that had never been witnessed before, but only theorized about. This type of explosion is called a "pair-instability supernova" and it might have been common in the early universe when more massive stars reigned.
SN 2006gy
The supernova has been named SN 2006gy. It was first spotted by Robert Quimby on September 18, 2006. A team that studies supernovae that is led by Alex Filippenko then turned multiple telescopes toward this supernova. They found that the supernova slowly brightened over the course of 70 days to its peak, and then stayed brighter than any supernova previously seen for more than three months. Now, more than eight months later, it still shines as brightly as a run-of-the-mill supernova would at its peak.
Pair-Instability Supernova
A typical supernova occurs at the end of a star's life. As the star exhausts its fuel supply in its core, fusion stops and the core collapses inward. The outer layers of the star explode outward but the core condenses into a neutron star or black hole. In a pair-instability supernova, the star is much more massive than typical stars of today. The temperature in the interior of the star becomes so intense that before the star can run its course of fusion, high-energy gamma rays form matter-antimatter pairs and annihilate one another. Because gamma radiation is what keeps the outer layers from collapsing inward, with the drop in energy the core is able to fall inward prematurely. This leads to a thermonuclear explosion that shreds the entire star, flinging its entire content into space, and leaving behind no remnant whatsoever.
The Early Universe
A star that resulted in SN 2006gy is similar to stars in the early universe because of its large size. It is believed that early stars were much more massive and the matter from their explosions is what seeded the universe with heavy elements. All the heavy elements you see today, from houses to humans to planets, originated from this early generation of explosive stars.
"We may have witnessed a modern-day version of how the first generation of the most massive stars ended their lives, when the universe was very young," says Filippenko.
UC Berkeley post-doctoral fellow Nathan Smith explains the differences between a standard supernova and the new type discovered. "In terms of the effect on the early universe, there's a huge difference between these two possibilities. One pollutes the galaxy with large quantities of newly synthesized elements, and the other locks them up forever in a black hole. One exciting repercussion of this is that, if pair-instability supernovas really are this bright, it gives us hope that the James Webb Space Telescope might actually be able to detect these explosions from the first stars, thereby verifying that they may actually exist."
The James Webb Space Telescope is a powerful tool that is planned for launch in 2013.
New Supernova Explosion Closer to Home?
SN 2006gy lies 240 million light-years away. But a closer star, named Eta Carinae, may await a similar fate. Discussing the new supernova, Filippenko says, "this is also very exciting because it suggests that Eta Carinae, only 7,500 light-years away, might possibly explode in a similar manner, becoming a spectacularly bright star in our sky."
Astronomer Mario Livio says that "Eta Carinae's explosion could be the best star-show in the history of modern civilization."
