Asteroid hunt: What else is coming our way?

Astronomers track objects that could collide with Earth

The asteroid Apophis, named after an Egyptian god representing darkness and chaos, has, at the moment, a 1-to-45,000 chance of striking Earth in 2036. But those odds will soon change, probably in a good way for mankind, while the hunt for near-Earth objects continues.

It is an effort that involves scientists like David J. Tholen, one of the astronomers credited with finding Apophis. It also includes the planned construction of a massive telescope on a mountaintop in Chile and the creation of what may be the world's largest database. Even Google Inc. has entered the picture.

Tholen, who has a Ph.D. in planetary sciences, and his team discovered Apophis in June 2004. The asteroid has been traveling the heavens for eons, but what is alarming isn't so much the odds that it might strike Earth, but that it was only recently discovered as a possible threat.

Apophis is located in a part of the solar system that makes it difficult to detect because it travels in the daytime side of Earth. Apophis will spend 95% of its time on the side of the sky that has the sun in it, Tholen said. "Are there other objects like it that we haven't found yet? Almost certainly."

"Could one of those objects sneak up on us from the daytime side and smack us without us being aware?" Tholen asked. He successfully sought funding from NASA to explore those areas of space where detecting asteroids is difficult because of the sun. The only time these objects can be viewed is a couple of hours after sunset and couple of hours before sunrise. Anything visible looks more like a crescent moon than a full moon, "so the objects that you are trying to find are fainter still."

Apophis made news this month when the Association of Space Explorers, a Houston-based group that includes Russians and Americans who have flown on space missions, urged the United Nations (PDF format) to organize efforts to thwart Apophis and anything else potentially hurling this way.

"Apophis isn't the only threat, it's only one," said Andy Turnage, executive director of the association, "the vast majority of which haven't been identified."

IT systems will a play role in discovering future threats. In particular, there's an effort called the Large Synoptic Survey Telescope (LSST), involving 20 universities and national labs to build a large telescope on a 8,800-foot mountain peak in northern Chile, called Cerro Pachon. This telescope will have the potential of finding asteroids as small as 100 meters.

Once it begins operation in 2013, the LSST is expected to generate 30,000GB of data per night. In total, petabytes (1PB equals 1 million gigabytes) of data will be created in what may well become the world's largest database. The project is expected to cost about $467 million, said Donald Sweeney, LSST project manager.

Google joined the effort last month. "They are going to help us with how the data is served and indexed -- how do you find stuff in petabytes of data," Sweeney said.

Meanwhile, Apophis speeds through space. At 1,000 feet in diameter, it has the potential of causing considerable damage, but the odds are that it won't hit Earth.

For a brief period in December 2004, the odds of Apophis hitting Earth were estimated at 1-in-37 but changed as more observations were recorded. The 1-in-45,000 figure will change yet again, and it's expected that Apophis will become less of a threat, not more, as time goes on, Tholen said.

Brian Marsden, who recently retired as director of the Minor Planet Center at the Smithsonian Astrophysical Observatory at Harvard University, but remains involved in its work, said the probabilities frequently change substantially with increased observations.

Apophis "won't be dangerous ... at least not for centuries to come, millennium to come," Marsden said.

Copyright © 2007 IDG Communications, Inc.

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