Pint-Size Sky Watchers
While monster telescopes get the attention, the little guys quietly — and cheaply — rack up cosmic finds.
- By Damond Benningfield
- Air & Space magazine, November 2012
(Page 3 of 4)
After the instruments completed observations on October 5, 2008, the project’s software reported the night’s findings to the Minor Planet Center at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, an international clearinghouse for asteroid and comet data. The center’s computers calculated preliminary orbits for the new discoveries, and found that one of them, 2008 TC3, was headed straight for Earth. Scientists at NASA’s Jet Propulsion Laboratory in Pasadena, California, quickly confirmed the orbit.
“I got an e-mail about 10 o’clock that morning from Donald Yeomans at JPL saying that we’d found one that was going to hit the Earth that night,” recalls Ed Beshore. Calculations showed the asteroid, which was about the size of an SUV, would enter the atmosphere above Sudan (see “Fireball!” Apr./May 2009). “A couple of KLM pilots saw it,” says Beshore, “and so did a couple of men at a railroad station out in the desert. A few months later, an expedition went out into the desert and found about 10 kilograms [22 pounds] of fragments. It was the first time anyone had found meteorites from an object that had been observed before it hit Earth.”
A couple of years ago, astronomers from the California Institute of Technology realized the Catalina database contained other valuable nuggets: observations of events so violent or energetic they can be seen only for a short time. The two teams compiled a list of thousands of these objects, known as transients. They are giant stars that pulse light like beating hearts, or titanic stellar explosions known as supernovas, or even flickers of gas spiraling into a supermassive black hole at the center of a galaxy. “The transient universe is the new big thing,” says Larson.
The most enigmatic transients were the targets of another early small telescope network, ROTSE (Robotic Optical Transient Search Experiment). Established by University of Michigan physicist Carl Akerlof, it highlights a couple of the traits that small telescope operators must have to be successful: perseverance and adaptability.
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.