University Communications

Winter 1998
Rising Star
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Just getting a clear view of the center of our galaxy was, in itself, a remarkable accomplishment. Turbulence from the Earth's atmosphere distorts the resolution of even the most powerful ground-based instruments. "It's as if you are looking at something at the bottom of a pond," Ghez says. To overcome that distortion, Ghez made her observations using a technique called "infrared speckle interferometry." This procedure, which she helped to develop, uses computers to analyze thousands of high-speed, high-resolution snapshots. The result: an image that has at least 20 times better resolution than those made by traditional earthbound imaging techniques.

"It's like putting on glasses," says Ghez.

The technique involves working out the timescale on which the atmosphere is introducing the errors -- in the realm in which she was scanning, that was about one every 100 milliseconds -- and then taking and saving pictures at that interval. Employing a variety of correcting techniques, she produced "diffraction-limited" images: On the screen of her computer, blurry "before" images were shrunk to pin-pricks, giving her the highest spatial resolution currently attainable from the ground or space.

What Ghez had achieved was amazing. The innermost stars in Ghez's survey moved 3 million miles an hour across space. Light is 200 times faster. From earth (moving 19 miles each second around the sun at a mere 68,000 miles per hour), Ghez had to derive those distant suns, all of which register as less than a glimmer, even if the telescope could find them. The precision of Ghez's measurement at the border of the Milky Way's black hole was such, says UCLA colleague Eric Becklin, "that an observer in L.A. could measure someone in New York turning his head back and forth."

Her observations -- captured in two- or three-day increments every month or so during the course of the year -- have revealed insights into our own galaxy that heretofore could only be inferred and supports findings from other research groups reported earlier this year.

"There is an incredible amount of matter between us and the center of the Milky Way to obscure our view," NSF's Oswalt says. "Andrea has pulled the living-room shades open a bit and finally given us a good look at what's going on in our own backyard."

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