In an unprecedented event, two asteroids will pass our planet Wednesday at a distance closer than the moon. Neither rock threatens to strike the earth, say astronomers.
In an unprecedented event for astronomers, two asteroids will swing past the Earth Wednesday at a distance closer than the moon.
The two asteroids, which will not be visible to the naked eye, were only recently discovered by astronomers with the Mount Lemmon Survey in Tucson, Ariz. They are in different orbits with close passes that will come nearly 11 hours apart. While scientists say neither threatens to strike the planet, the two space rocks do provide a challenging skywatching opportunity.
Other asteroids have been known to make such close passes, but it is rare for two to be spotted zooming in at the same time. Because of the asteroids' movement, finding and tracking them across the sky will be a challenge for seasoned skywatchers. [Image Gallery: Asteroids]
The smaller asteroid, 2010 RF12 will have a closer pass, at almost 49,000 miles (about 79,000 km).
This is higher than communications satellites in geosynchronous orbit 22,369 miles (36,000 km) above Earth. On average, the moon is about roughly 238,600 miles (384,000 km) from Earth, so 2010 RF12 will pass by at nearly 0.2 of that lunar distance.