Arianna's Comet

Well, it was almost her comet. Turned out to be a galaxy instead. But "there's still more space to search."

Arianna Gleason started at the University of Arizona-Tucson on her 18th birthday. By the next week, she'd landed -- more accurately, launched -- a research position with the NASA-sponsored Spacewatch program. And in late September, on her first all-nighter at the big telescope on top of Kitt Peak, she spotted something that looked like a brand-new comet.

Everybody was all excited, and for two dizzying weeks, Gleason processed, enlarged and purified images from the telescope's camera, dreaming all the while about going home for Christmas and announcing that a comet would be named after her.

Alas, Arianna's comet turned out to be merely a faraway galaxy (news her Webster Groves family heard as, "Arianna's discovered a galaxy!"). But she's still blissful about staying up all night looking for near-earth asteroids (NEAs), faraway asteroids and trans-Neptunian objects (TNOs, objects that have crossed the orbit of Neptune).

"We go up the mountain around 5 p.m., wearing really heavy clothes, jeans and layers of sweatshirts," she explains happily. "First you have to focus the telescope and align it, then align all the other electronics so it's ready as soon as the sun goes down." Lights are restricted in Tucson, especially on Kitt Peak, so the night sky's velvety black, "so dark, the stars are just falling on you. The sky's just littered with them."

Gleason's young; even the observatory's many flights of stairs fuel her imagination. "From the ground, you go up two flights to the control room, then one more to where the telescope sits, then crawl up three or so ladders to the platform of the telescope, where our camera is," she relates eagerly. "Before you can start observing, you have to cool down the camera with liquid nitrogen, because if it's warm you get this chromatic aberration; the warmth creates waves in the pictures.

"So we're up on the mountain and we kind of take turns doing passes with the camera, to notice if anything is moving. We take three passes over the same region of space." The changes are infinitesimal, maybe three pixels total, in the three images recorded by the telescope camera. "We look for these TNOs, these really small objects that are very, very far away, which means they don't move much in our image. Then there are the main-belt asteroids; they move quite a bit in our field of view."

That first night's almost-comet was an understandable miss: It was only two years ago that the Hubble Space Telescope revealed the existence of at least 40 billion more galaxies than astronomers had suspected. "The initial pictures are very raw," Gleason explains. "There is a lot of noise in them. When you're doing a pass, you sit in front of the computer and if you see something interesting, you can highlight it with the mouse." But the computer can also catch "something stupid, like diffraction spikes from bright stars." And the calculations are a high-wire act, the slightest misjudgment disastrous. "Earlier this year, there was a big scare -- people from the University of Arizona supposedly found an asteroid and thought it was going to hit the earth, and the media made a big story about it, but they were a little off. Millions of very small meteorites hit the earth every day, cosmic dust," adds Gleason, who watched the recent Leonids meteor shower in the blackness of the desert.

Even better, though, is crawling out the hatch and sitting on the domed top of the observatory. "It's really cold," she says with a smile. "But I don't think I have ever felt such a feeling of peace and pure happiness. It was so wonderful I could taste it. It was like being on top of the world." And then the world moved beneath her. "Nicole had to adjust the dome," she grins. "Every time we find a new area of space, the telescope changes position a little bit, so we have to move the dome. She started spinning it while I was up there, and I kind of had to hold on. It moves very slowly, but it was still exhilarating!"

The Spacewatch director, Dr. Jeff Larson (who's found one or two comets on his own, Gleason notes), has written elaborate computer programs to track TNOs and other bodies. Gleason had to learn, quickly, all these "alpha programs, which have just been born." But Larson had been impressed with her earlier calculations of stellar distances on a project at the University of Missouri-Columbia when she was a junior in high school. "They were pretty good numbers I came up with," she admits, "5-10 percent error, and when you're talking light years, that's pretty good!

"It's called astrometry, measuring the size and trajectory of asteroids," Gleason adds helpfully. "If the previous team has found anything interesting, we do what are called 'recoveries' of their objects, using the 'RA' and the 'dec.'" (That's the right ascension and the declination, the coordinates used to map the cosmos.) "We need to know the date it was found, and the time, and then we are able to find it again. And we also scan new areas of space, hopefully where no one else has looked.continued on next pagecontinued from previous page

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