Two billion years ago, in a far-away galaxy, a giant star exploded, releasing almost unbelievable amounts of energy as it collapsed to a black hole. The light from that explosion finally reached Earth at 6:37 a.m. EST on March 29. The intense flash of gamma radiation was first detected on 29 March by NASA’s Earth-orbiting High-Energy Transient Explorer (HETE-2) satellite, but human intervention was required to find the exact location. Once they did, the Robotic Optical Transient Search Experiment (ROTSE) and its two telescopes separated by about 110 degrees longitude swung into action to record one of the most continuous records of this explosion. Despite sporadic clouds and rainstorms in Australia, the ROTSE instrument at Siding Spring Observatory in northern New South Wales was able to record the decaying light from the blast. Twelve hours later, the second ROTSE telescope in Fort Davis, Texas was picking up the job of monitoring this spectacular explosion. “Installations in Namibia and Turkey will follow soon. Our goal is to have telescopes continuously trained on the night sky. Our motto is “The Sun never rises on the ROTSE array,” said Carl W. Akerlof at the University of Michigan and the leader of ROTSE.
Gamma ray bursts are the most powerful explosions in the universe, but they are extremely hard to study because they are extremely distant, occur randomly in time and seldom last more than a minute. Small, fast, and relatively inexpensive robotic ground-based telescopes like ROTSE offer the best chance of catching early optical emissions from the bursts.
“The optical brightness of this [March 29] gamma ray burst is about 100 times more intense than anything we’ve ever seen before. It’s also much closer to us than all other observed bursts so we can study it in considerably more detail,” said Akerlof. ROTSE teammember Michael Ashley noted, “During the first minute after the explosion it emitted energy at a rate more than a million times the combined output of all the stars in the Milky Way. If you concentrated all the energy that the sun will put out over its entire 9 billion-year life into a tenth of a second, then you would have some idea of the brightness.” The unusual outburst has been dubbed a hypernova.