Wednesday, June 4, 2014

Astronomers detect Light from Gamma Ray Burst from huge explosion 12 billion years ago

Light from the explosion 12 billion years ago of a massive star at the end of its life reached Earth recently. 

An image of its peak afterglow, circled with blue and yellow, was captured by Southern Methodist University's ROTSE-IIIb telescope at McDonald Observatory, Fort Davis, Texas. 

A bright star sits alongside the afterglow from GRB 140419A


Known as a gamma-ray burst, the intense light captured in the night sky resulted from one of the biggest and hottest explosions in the universe, occurring shortly after the Big Bang.

Intense light from the enormous explosion of a star more than 12 billion years ago, shortly after the Big Bang, recently reached Earth and was visible in the sky.

Known as a gamma-ray burst, light from the rare, high-energy explosion traveled for 12.1 billion years before it was detected and observed by a telescope owned by Southern Methodist University, Dallas.

Gamma-ray bursts (GRBs) are believed to be the catastrophic collapse of a star at the end of its life. SMU physicists report that their telescope was the first on the ground to observe the burst and to capture an image, said Farley Ferrante, a graduate student in SMU's Department of Physics, who monitored the observations along with two astronomers in Turkey and Hawaii.

Recorded as GRB 140419A by NASA's Gamma-ray Coordinates Network, the burst was spotted at 11 p.m. April 19 by SMU's robotic telescope, ROTSE-IIIb, at the McDonald Observatory in the Davis Mountains of West Texas.

Gamma-ray bursts (GRBs) are not well understood by astronomers, but they are considered important, Ferrante said.

"As NASA points out, gamma-ray bursts are the most powerful explosions in the universe since the Big Bang," he said. "These bursts release more energy in 10 seconds than our Earth's sun during its entire expected lifespan of 10 billion years."

Some of these gamma-ray bursts appear to be related to supernovae, and correspond to the end-of-life of a massive star, said Robert Kehoe, physics professor and leader of the SMU astronomy team.

"Gamma-ray bursts (GRBs) may be particularly massive cousins to supernovae, or may correspond to cases in which the explosion ejecta are more beamed in our direction. By studying them, we learn about supernovae," Kehoe said.

Scientists weren't able to detect optical light from gamma-ray bursts until the late 1990s, when telescope technology improved.

Among all lights in the electromagnetic spectrum, gamma rays have the shortest wavelengths and are visible only using special detectors.

SMU's ROTSE-IIIb at the McDonald Observatory, Fort Davis, Texas had the earliest and brightest observation from the ground of a gamma-ray burst that occurred more than 12 billion years ago. 

The telescope is part of the Robotic Optical Transient Search Experiment, which has telescopes in four locations on Earth to cover the entire sky in search of gamma-ray bursts. 

Credit: ROTSE Collaboration.

Gamma-ray bursts (GRBs) result from hot stars that measure as enormous as 50 solar masses. The explosion occurs when the stars run out of fuel and collapse in on themselves, forming black holes.

Outer layers detonate, shooting out material along the rotation axis in powerful, high-energy jets that include gamma radiation.

As the gamma radiation declines, the explosion produces an afterglow of visible optical light. The light, in turn, fades very quickly, said Kehoe.

Physicists calculate the distance of the explosion based on the shifting wavelength of the light, or redshift.

"The optical light is visible for anywhere from a few seconds to a few hours," Kehoe said. "Sometimes optical telescopes can capture the spectra."

"This allows us to calculate the redshift of the light, which tells us how fast the light is moving away from us. This is an indirect indication of the distance from us."

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