Asteroid Flying By Earth Tomorrow Has Its Own Moon.

Asteroid 1998 QE2 will be making a close approach to Earth tomorrow. Well, close in space terms, anyway. The large asteroid will be 3.6 million miles away at its closest point.  Still, Astronomers at NASA’s Jet Propulsion Laboratory have been keeping a close eye on it thanks to its proximity. Yesterday, as those astronomers were observing the asteroid, they discovered that QE2 isn’t just heading our way – it’s bringing its own moon along for the ride.

That’s actually not that unusual, either. About 16% of the large asteroids near Earth have one or sometimes even two moons.

QE2 is about 1.7 miles in diameter. Its moon, or companion asteroid, is about 2,000 feet in diameter – about 22% of its side. Images of the asteroid and its moon were captured using radar images from the Deep Space Network antenna in California.

The astronomers will keep monitoring the asteroids with radar images as it gets closer, giving astronomers more and more information about them. Although we’re used to thinking of radar images as either blips on a screen in a movie or cloud coverage in weather photos, radar can be used to gather detailed information about asteroids. Such information includes an asteroids size, its shape, and even some of its features.

Radar tracking is also used to calculate the orbit of asteroids, with a particular eye to seeing if any such asteroids pose a danger to Earth. NASA’s tracking systems have discovered about 98% of the asteroids believed to be near the Earth. This tracking is supplemented with data from the Wide-field Infrared Survey Explorer, which found in 2011 that there were fewer near Earth asteroids than had previously been supposed.

After QE2 makes its close approach to Earth tomorrow, it will be awhile before we get another good a look at it or its moon. NASA estimates that it will be over two centuries before the asteroid comes this close to Earth again.