Pint-Size Sky Watchers

While monster telescopes get the attention, the little guys quietly — and cheaply — rack up cosmic finds.

HATSouth telescopes search for dim planets orbiting the stars in Chile’s Atacama desert sky. (Gáspár Bakos)
Air & Space Magazine

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In 1991, after the launch of NASA’s Compton Gamma Ray Observatory, Akerlof became interested in gamma-ray bursts: explosions that produce brief outbursts of the most powerful form of radiation. Astronomers didn’t know what caused them, in part because they happened so quickly and didn’t repeat, so it was difficult to pinpoint their location. Telescopes like Compton could catch them, but there just isn’t enough detail in the burst of radiation to tell astronomers much about the source. Scientists theorized that if they could localize the gamma-ray bursts faster, they might find an afterglow, the fading emission of light in lower-energy wavelengths—in particular, the optical wavelengths—which could give away a wealth of details, such as the source’s distance and its energy. In 1997, astronomers finally detected an afterglow; they now had a key to understanding these cosmic phenomena, but needed a reliable way to collect more data.

Akerlof began looking for a way to build a small, automated telescope to swiftly search for the optical hangers-on. He was on sabbatical at Livermore National Laboratory at the time, and soon heard of a telescope system the lab had built for the Pentagon’s 1980s-era Strategic Defense Initiative (known as “Star Wars”). “I thought it would be all hush-hush, and the chances of seeing it would be extremely remote,” Akerlof says. “But I mentioned it to somebody and he said, ‘Yeah, I worked on it. It’s sitting in a warehouse now, not doing anything. Do you want to see it?’ ” Akerlof began adapting it to search for gamma-ray bursts, but he knew from the start it wouldn’t have sufficient image quality. “For $10 million, it was not very impressive,” he says.

Instead, he built a system using four Canon telephoto lenses, “the kind they rent to private detectives who are working nasty divorce cases.” With this system and a little luck—just after he started operations, one of the most powerful gamma-ray bursts ever recorded occurred—in 1999 Akerlof made the first prompt-response detection of a gamma-ray burst’s optical afterglow. But Akerlof knew he would need a more powerful instrument, so he commissioned a half-meter telescope. “The [telescope builders] did a crappy job, so the best decision I ever made was to throw it away and start over. I had to stick my nose in a lot of places I thought I’d never go.... And I didn’t have an infinite amount of money to spend, but that was probably a blessing.”

After a few more false starts, Akerlof dove into the world of telescope manufacturing, made friends and learned the trade, and eventually pieced together the four 18-inch telescopes that now make up ROTSE. He set them up in Texas, Turkey, Australia, and Namibia, a distribution that ensures that at least one telescope is in darkness. (“The sun never rises on the ROTSE empire,” he jokes.) Each telescope is linked to a NASA alert system, which sends out a notice when space-based telescopes detect a gamma-ray burst, and can slew to look at that point in the sky within about seven seconds.

ROTSE’s years of observations have helped show that the blasts are far outside the Milky Way galaxy—some are billions of light-years away. That telescopes can detect them from such a great distance means they must be extremely powerful. Scientists now know that a gamma-ray burst releases more energy in one minute than our sun will produce in its entire lifetime of more than 10 billion years. Some form when a powerful stellar explosion beams a narrow “jet” of gamma-rays into space from its poles. Other bursts happen when two ultra-dense neutron stars collide, their magnetic fields twisting together and releasing gigantic blasts of energy.

When Gáspár Bakos began thinking about building his own small, automated telescopes, gamma-ray bursts were his original target too. Colleagues convinced him, however, that too much money and effort were going into the hunt for a then-22-year-old graduate student to compete. So Bakos turned to a field that was just gearing up: searching for planets in other star systems.

He started developing a telescope in 1998, and recruited friends to help him build it. They used second-hand lenses, the windshield-wiper motor from an old Russian truck to power the dome, and electronics they built themselves. “We were using primarily our own money, so the whole philosophy was to make it work without any money,” he says. And they did, for just a few thousand dollars—pennies when compared to, for example, the $20 million MMT. “We took a picture of the Andromeda galaxy with it. It was a noisy image—you can get a better image through binoculars. But it tracked the target, it took the image, it read it out, it displayed it.”

Bakos spent a summer testing and improving the HAT prototype at Konkoly Observatory in Hungary, then, with funding from Princeton, moved it to Kitt Peak National Observatory in Arizona in 2001. A fellowship from the Smithsonian Astrophysical Observatory, which runs Whipple, let Bakos expand HATNet—now officially a network—to five telescopes. NASA helped set up HATNet in Hawaii, and after nearly a decade of studying the northern sky, Bakos established HATSouth in the Southern hemisphere. HATSouth uses a pair of telescope mounts at each location, each with four eight-inch telescopes that work together to create a wide-field mosaic of the sky.

Each night brings new challenges, of course. In Arizona, Bakos points out pine trees that emit puffs of pollen at night, coating the delicate telescope lenses with a yellow film. And a U.S. Customs and Border Patrol station in the desert far below the mountaintop turns on lights bright enough to cast shadows on his telescope domes. Each discovery also requires the use of big telescopes for confirmation, which plunges Bakos into competition for precious telescope time.

Yet, as Akerlof notes, those who operate small telescopes enjoy a luxury that those who run shared giant telescopes do not: They get to make their own decisions. Like walking away.

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