Brightest Known Supernova Detected

Anne Minard
for National Geographic News
October 15, 2007
Scientists have spotted the brightest supernova yet—a star explosion that at its peak was a hundred billion times brighter than the sun.

Robert Quimby, an astronomer at the California Institute of Technology, discovered the spectacle in 2005 using a small robotic telescope at McDonald Observatory in West Texas.

But only recently did he calculate the true power of the supernova, known as 2005ap.

The explosion is 300 times brighter than average and is the most luminous supernova ever identified, Quimby said.

"It's amazing to me that after decades of in-depth studies, the brightest and seemingly most obvious supernovae are still being found," he added.

2005ap lies about 4.7 billion light-years away in a dwarf galaxy in the constellation Coma Berenices, behind the famous Coma cluster of galaxies.

The new find is a Type II supernova. These explosions are thought to occur when the cores of massive stars—more than seven times as heavy as the sun—collapse under their own weight and trigger an explosion.

A study on the supernova will appear in the October 20 edition of Astrophysical Journal Letters.

Two in a Row

For Quimby, the discovery is almost a hat trick.

The new supernova is roughly twice as bright as the previous record holder, SN 2006gy—which he also found. (Related: "'Brightest Supernova Ever' Reveals New Kind of Star Death [May 8, 2007].)

Quimby discovered that explosion last year while working on the Texas Supernova Search project, part of his doctoral degree program at the University of Texas.

He actually observed supernova 2005ap there before 2006gy. But only recent follow-up studies that pinpointed distance revealed 2005ap's true power.

"There's no question that [his results] have gotten everybody's attention," J. Craig Wheeler, Quimby's colleague and a supernova expert at the University of Texas at Austin, said in a press release.

On the Hunt

Supernovae are rare events, occurring roughly twice a century in a galaxy like the Milky Way.

Researchers study them for insights into the fates of stars bigger than our sun. The explosions also serve as evidence that the expansion of the universe is accelerating, because the most distant ones appear dimmer than expected.

Supernovae are also the only way elements heavier than iron are seeded throughout the universe and play a vital role in the evolution of galaxies, Quimby said.

"Plus, they're huge explosions, and that's just cool," he said.

Despite their massive size and power, however, finding supernovae amidst the glare of other cosmic objects isn't easy.

Galaxies get much brighter toward their cores, which can wash out the contrast of a new supernova, Quimby said.

The University of California's Lick Observatory Supernova Search actually studied the area containing 2006gy before him, Quimby said, but missed it because they couldn't distinguish the explosion from its galaxy's brilliant core.

Quimby said part of his supernova-hunting success is his technique. He checks dwarf galaxies as well as galaxies with active black holes at their centers, which other studies avoid, raising the possibility of discovering new types of supernovae previously overlooked.

2006gy, for example, was found in the core of a galaxy with a weak central black hole.

"I've worked too damn hard for this to be luck," he said.

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