Advertisement

Feature: Scrambling to study a 'hypernova'

By
PHIL BERARDELLI, UPI Deputy Science and Technology Editor

Two billion years ago, in a galaxy far, far-away, a giant star exploded, releasing staggering amounts of energy as it collapsed into a black hole.

Normally, the light from such an ancient and distant cataclysm would take earthbound astronomers by surprise and be gone before it could be recorded. But this time, when it finally reached Earth on the morning of March 29, astronomers were ready.

Advertisement

Not merely a supernova, the titanic destruction of a star that releases in a moment the energy of a billion suns, scientists call the newly observed -- and much, much bigger -- phenomenon a hypernova.

First recorded by NASA's orbiting High-Energy Transient Explorer-2, a small scientific satellite intended to detect mysterious cosmic events called gamma ray bursts, HETE-2 quickly alerted a special team of ground-based astronomers who scrambled to activate a planet-spanning effort to capture the rare and rapidly decaying explosion.

Despite intermittent clouds and rainstorms, an instrument at Siding Spring observatory in Australia's northern New South Wales was able to collect light from the blast. Then, 12 hours later, a second telescope, located about 9,000 miles away in Fort Davis, Texas, picked up the remnants of the fading event.

Advertisement

What the instruments collected was nothing short of spectacular.

"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, said Michael Ashley, with the astrophysics and optics department at the University of New South Wales and a member of the team of astronomers who studied the hypernova.

"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," Ashley said.

"The optical brightness of this gamma ray burst is about 100 times more intense than anything we've ever seen before," said Carl W. Akerlof, the team leader and an astrophysicist at the University of Michigan in Ann Arbor.

However, exceptional brightness is not the only unique characteristic of the hypernova.

"It's also much closer to us than all other observed bursts so we can study (its aftermath) in considerably more detail," Akerlof explained.

Even though they are the most powerful explosions in the universe, gamma-ray bursts have been difficult to study because they usually are extremely distant, occur randomly and seldom last more than a minute. So astronomers, supported by NASA and the National Science Foundation, developed a counter-strategy.

Advertisement

Called ROTSE, for Robotic Optical Transient Search Experiment, the effort consists of a loosely connected array of small, fast, and relatively inexpensive ground-based telescopes placed all over the globe. ROTSE attracted attention in 1999 when it captured the rise and fall of GRB990123, one of the brightest bursts prior to the hypernova.

"The ROTSE equipment is quite modest by modern standards, but its wide field of view and fast response allow it to make measurements that more conventional instruments cannot," Akerlof said. "We have two telescopes online now, and 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.' That's why we want them spread as widely as possible."

Akerlof said another role for ROTSE and other small telescopes is to alert larger facilities about gamma ray bursts and similar events. "One of the most exciting things about an event like this is the way the global community of scientists pulls together, pooling their data and their different capabilities," he said.

Latest Headlines