SCIENCE NOTEBOOK

Asteroid to Miss Earth Tonight

If you feel a little breeze tonight, look up.

An asteroid as wide as the length of three football fields will be speeding past Earth at the astronomical equivalent of a rather close shave: less than one-and-a-half times the distance to the moon.

Okay, that's not close enough to cause a breeze. And it won't be visible without the help of a telescope. But near-Earth asteroids are unusual enough to have astronomers excited about the event. Among the hundreds of asteroids being tracked, the next of this size or larger to pass this close will not arrive until 2027.

That is why scientists at the Arecibo Observatory in Puerto Rico will be training their instruments on the craggy piece of space debris known as 2007 TU24 to study its features and trajectory.

Scientists at Cornell University, which operates Arecibo for the National Science Foundation, emphasized that TU24 poses no threat. A miss is as good as a mile, after all, and in this case, we're talking about 334,000 miles.

But only two telescopes on the planet can examine such objects in detail -- those at Arecibo and NASA's Goldstone facility in California. Both use radar, a wavelength that can tell with great precision an asteroid's contours, its path through space and how it is spinning.

Goldstone devoted a couple of days to TU24 last week, but Arecibo has the more sensitive instrument, able to discern details as small as 25 feet across. Its radar "allows very accurate predictions of the future orbits of near-Earth asteroids, enabling a much better assessment of the likelihood of an impact with Earth," Cornell astronomy professor Donald B. Campbell said.

-- Rick Weiss

Female Birds Size Up Males

A female bird's taste in males can change radically from year to year. But fickleness or faddishness are not the reasons. Her preferences, instead, arise from another inscrutable attribute: female intuition.

She infers from a long list of fashion choices in her potential mates which combination is most likely to add up to the most chicks at the end of the season.