So is there any chance that Toutatis may hit Earth in the future?
"The answer is obviously, yes," Ostro said. "There's a good chance [of Earth impact] in the next several tens of millions of years. But you could make that statement about any one of the near-Earth asteroids."
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Observing Toutatis
Despite NASA's assurances that Toutatis poses no immediate threat of impacting Earth on Wednesday, doomsday predictions spreading via chain e-mail earlier this year put the chances of impact at 63 percent.
Alan MacRobert, senior editor for Sky and Telescope magazine, noted in a recent article for the magazine that while such doomsday predictions are false, Toutatis does whiz close enough to Earth to make a "fine observing challenge for telescope users."
The best opportunity for Northern Hemisphere viewers using at least a four-inch (ten-centimeter) telescope will be a few days prior to the asteroid's closest approach, when Toutatis will cross the southern portion of the constellation Capricornus.
MacRobert writes that on the night of its closest approach, the asteroid will be visible from the Southern Hemisphere, where it will pass within one degree of the star Alpha Centauri.
Early next month Ostro and his colleagues will make additional radar observations of Toutatis using the Arecibo telescope in Puerto Rico. Their main goal is to determine the asteroid's mass using an experiment based on the Yarkovsky effect.
The Yarkovsky effect is a force produced by the manner in which an asteroid absorbs energy from the sun and reradiates it into space as heat. "If we can model the force adequately, then we can [determine Toutatis's] mass by analyzing very precise radar measurements," Ostro said.
Measuring the asteroid's Yarkovsky effect will also help astronomers to better refine their predictions of the asteroid's orbit. With that information, scientists can calculate if, and/or when, Toutatis poses a real risk of impacting Earth.
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