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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.
like putting on glasses," says Ghez.
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.
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."
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.
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."