Washington, January 5 (ANI): A team of astronomers has discovered a distant star that exploded when its center became so hot that matter and anti-matter particle pairs were created.
The finding was made by University of Notre Dame astronomer Peter Garnavich and a team of collaborators.
The star, dubbed Y-155, began its life around 200 times the mass of our Sun but probably became "pair-unstable" and triggered a runaway thermonuclear reaction that made it visible nearly halfway across the universe.
Garnavich and his collaborators discovered the exploding star during the "ESSENCE" supernova search that identified over 200 weaker stellar explosions.
"ESSENCE found many explosions in our 6 years of searching, but Y-155 stood out as the most powerful and unusual of all our discoveries," said Garnavich.
Y-155 exploded about 7 billion years ago, when the universe was half its current age.
It was discovered in the constellation Cetus (just south of Pisces) with the National Optical Astronomy Observatory's (NOAO) 4-m Blanco telescope in Chile in November of 2007 during the last weeks of the six-year ESSENCE project.
The Keck 10-m telescope in Hawaii, the 6.5-m Magellan telescope in Chile, and the MMT telescope in Arizona rapidly focused on the new star, revealing that the wavelengths of light emitted from the supernova were stretched or "redshifted" by 80 percent due to the expansion of the universe.
Once the distance to the explosion was established, Garnavich and his collaborators calculated that, at its peak, Y-155 was generating energy at a rate 100 billion times greater than the sun's output.
To do this, Y-155 must have synthesized between 6 and 8 solar masses of radioactive nickel.
A normal "Type Ia" thermonuclear supernova makes about one tenth as much radioactive nickel.
"In our images, Y-155 appeared a million times fainter than the unaided human eye can detect, but that is because of its enormous distance," Garnavich said.
"If Y-155 had exploded in the Milky Way, it would have knocked our socks off," he added.
The ESSENCE project was designed to precisely map the expansion history of the universe by discovering type Ia supernovae and using them as distance markers.
The ultimate goal is to understand the mysterious dark energy that is driving the accelerating expansion. (ANI)