The University Record, February 22, 1999

Akerlof photographs 9-billion-year-old light surge

By Sally Pobojewski
News and Information Services

Carl Akerlof has earned the right to boast a little. Not only was he the first astrophysicist to photograph something that most experts in his field didn’t believe even existed, but he did it with a $200,000 telescope built from off-the-shelf components with no direct federal funding.

What Akerlof saw was a gamma ray burst—a sudden, intense surge of radiation and light created 9 billion years ago when the universe was about half as old as it is today. Scientists have been studying X-ray and gamma radiation from these powerful explosions for years, but until Jan. 23, no one had ever seen visible light with the X-ray signal. Many astronomers either doubted the existence of visible light from gamma ray bursts or believed it never would be possible to see it.

But they were wrong. At 4:08 a.m. on Jan. 23, light from the burst reached a telescope in the mountains near Los Alamos National Laboratory in New Mexico. Called ROTSE-1—for Robotic Optical Transient Search Experiment—the telescope was conceived and built by Akerlof and colleagues from the Department of Physics and the Department of Energy’s Los Alamos and Lawrence Livermore National Laboratories. Its purpose: To scan the sky twice each night and capture images of faint, transient objects.

The amount of energy released in a gamma ray burst is awe-inspiring. “A one-megaton thermonuclear explosion converts the mass equivalent of a bran muffin into energy all at once,” says Akerlof, professor of physics. “The amount of energy released in a gamma ray burst requires conversion of a mass equal to our sun.” If the Jan. 23 gamma-ray burst had originated within our Milky Way galaxy, Akerlof adds, it would have lit up the night sky.

Because the Jan. 23 burst was so far from Earth, Akerlof was surprised that the optical signal was brilliant enough to be visible through even an amateur telescope or pair of field binoculars. “We thought we’d have to dig the signal out of the dirt, but instead it whacked us in the face,” he says.

Astronomers have no accurate idea of what causes gamma ray bursts, but they know they show up about once a day at totally random locations throughout the universe. The trick is knowing exactly where to point your telescope to capture their powerful, but fleeting signals.

To pinpoint the Jan. 23 burst’s location, Akerlof and his colleagues had help from NASA’s orbiting Compton Gamma Ray Observatory, which picked up the initial X-ray emissions from the burst and automatically relayed the sky coordinates to ROTSE-1. Although no one was there to watch, ROTSE-1’s small camera array went into action, recording 150 images over the next one and one-half hours. When Akerlof logged into his U-M computer the following morning, images from the burst were waiting for him. Using more refined coordinates provided by a European satellite called Beppo-SAX, he easily located a star-like object where none existed two hours earlier.

After reviewing the data with Tim McKay, assistant professor of physics, and other ROTSE team members, Akerlof reported the first capture of optical images from a gamma ray burst on an Internet site for astrophysicists.

“It was amazing to me,” he says. “Here I was in my office interrogating a device 2,000 miles away and then publishing data around the world just 14 hours later.”

Congratulatory messages began arriving almost immediately, including some from former skeptics and one especially gratifying e-mail from an administrator at the National Science Foundation, which had repeatedly turned down Akerlof’s requests for funding.

The Jan. 23 images captured by ROTSE-1 will soon be available for study by other scientists. Akerlof hopes they will help solve some of the mysteries surrounding the origin of gamma ray bursts and how they release enormous amounts of energy in such a short period of time. He also says ROTSE’s initial success is a good sign that more detailed images will be obtained with a more powerful telescope soon to become operational.

And to all those skeptics who said it couldn’t be done, Akerlof has just one comment: “In science, it helps to look occasionally, especially when the conventional wisdom counsels otherwise.”