See Near-Earth Asteroid Buzz Our Planet—Live

The asteroid Apophis, pictured here in three colors, will whiz by Earth later today. Image courtesy B. Altieri and C. Kiss, ESA/MPE/Konkoly

Sky-watchers can enjoy a close encounter today with an infamous asteroid once (erroneously) thought to pose a serious threat to Earth—the force of an impact would be like detonating tens of thousands of "Little Boy" atomic bombs. Slooh Space Camera will stream a live look at Apophis, which at a comfortable distance of 9 million miles (14.5 million kilometers), poses no present risk but still has an extremely remote chance of smashing into Earth on future passes.

"Back in 2004 when this asteroid was discovered there was concern that it had a relatively high probability of impacting Earth, a 1 in 45 chance during the 2029 flyby," said Slooh president Patrick Paolucci. "Fortunately they were able to determine that was inaccurate. But on that next approach in 2029, it's still going to be closer [to Earth] than our satellites. That's really why this event is on our radar."

Scientists will watch Apophis to better fine-tune its future path. Wednesday's pass could even influence the miniscule possibility (1 in 250,000 by NASA estimates) that the 885-foot (270-meter) rock might actually hit Earth in 2036. It would happen only in the extremely unlikely and unlucky event that Earth's gravity alters the rock's orbit in precisely the wrong way and creates a collision course.

Apophis is one of many asteroids orbiting between Earth and the sun that may pose future impact threats, and any close look is an opportunity to learn more about them.

"People may be surprised how many of these asteroids come whizzing past us and some of them are unexpected, which is scary," Paolucci said. "2012 LZ1, for example, was a big asteroid that was only discovered a few days before it flew by Earth. We streamed that live and it was a really cool show, but also an eye-opener for us. We want to cover these objects for the general public and bring awareness so that people can understand what's going on out there."

Slooh will capture and stream live images of the flyby from its high-altitude observatory on the island of Tenerife, in the Canary Islands. Free live shows with real-time discussion by Paolucci and others begin at 4 p.m. PST/7 p.m. EST on Slooh.com.

Brian Handwerk
for National Geographic News
Published January 9, 2013