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A Celestial News Bureau

Three Smithsonian astronomers run a worldwide news service about what is happening overhead

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The result is a huge increase in amateur and professional discoveries. "The number of supernovas has gone up by a factor of 4," notes Green. "In terms of comets, we're looking at a factor of 3."

Technology hasn't made only people better sky watchers, either. Across the hall from Marsden and Green, Gareth Williams swings his chair between two large computers, into which he swiftly types numbers. And more numbers. "I'm processing some 800 LINEAR observations," he says without pausing to look up, "from what was submitted from six nights of observation." Around him sit stacks and stacks of data on asteroids and other celestial objects found by an innovative computer- and CCD-driven telescope in Socorro, New Mexico, known as LINEAR. Since it began operations in 1997, LINEAR has discovered more than 50,000 minor planets in our solar system. (For anyone counting, that works out to about one-quarter of all minor planets discovered since 1925.)

As I watch, Williams' computers are engaged in an invaluable matching game, in which LINEAR's observations are compared with the orbits of known objects. The numbers are humbling. "This is not everything that LINEAR was doing for those six nights," Williams says. "We get 15,000 observations from them every day." He pauses long enough to grin ruefully at the paper mountains by his side. "I can get more from LINEAR in one night than I used to get in several months in 1990."

Of course, how news gets out to CBAT and MPC subscribers has undergone a revolution in itself. Less than 20 years ago, when e-mail was still evolving, telegrams were sent to the CBAT by astronomers with discoveries to report; the CBAT itself used telegrams to announce that news to the world. Those who could wait received their circulars as postcards.

Today, the "telegram" in the CBAT's name is a pleasant reminder of bygone technology. Astronomers rarely send reports by telegram when faster e-mail is available. And e-mail has supplanted telegrams as the main mode of distributing reports to subscribers, though postcards are still used. Not surprisingly, the Web is crucial. There, most of the CBAT and MPC reports are available, and ephemerides for unconfirmed near-Earth objects (NEOs) are posted for anyone to quickly update.

As the scare over XF11 proved, what the CBAT and MPC publish is hardly the stuff of astronomical esoterica. Before looking into relocating underground, however, one can get more details on close approaches in this century by looking at the MPC's compilation on the Web. There, I see, the half-mile-wide asteroid 1999 AN10 (discovered in January 1999 by LINEAR) could on August 7, 2027, come as close as 240,000 miles — as near as the Moon (gulp!).

"It can't hit us," Marsden reassures me, noting that the number listed is the smallest known distance from us. All information here is constantly updated by that valuable group of astronomers he, Green and Williams call on for just that. In AN10's case, helpful clarification of its minimum approach distance in 2027 came from amateur Frank Zoltowski. "We found that there was a lot of uncertainty about whether it will come close in 2027," Marsden says. "Frank's measurements made it clear that it would be well within a million miles. This actually increased the likelihood it could hit Earth in 2044. But with data gleaned by two amateurs from 1955 photographs, it became clear that AN10 will miss us by a large margin in 2044."

He pauses, then adds, "That's why we need to keep making observations: many people involved with discovery programs think that all you need to do is discover objects. But 1997 XF11 and 1999 AN10 show that we need to pay attention to what is found."

By Valerie Jablow

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