The huge-- 1.7 miles long, to be exact -- that is zipping by Earth this week isn't alone.
No, it isn't carrying an alien virus or a golden DVD containing the second season of "Firefly," but it does have a traveling companion. NASA radar images just released show a previously undiscovered moon orbiting the asteroid known as "QE2," technically making it a binary asteroid system.
The smaller asteroid circling its larger celestial road trip buddy is estimated to be about 2,000 feet wide.
This actually isn't that unheard of. NASA estimates that about 16 percent of larger (over 655 feet) near-Earth asteroids are binary or triple systems.
The closest approach of the space rockin' duo will take place Friday, May 31 at 1:59 p.m. PT, when the system will get no closer to us than about 3.6 million miles, or about 15 times the distance between Earth and the moon. This is likely the best view we'll ever get of QE2 in our neighborhood, as it isn't set to pass this close by Earth within the next 200 years.
You can see the radar images showing the smaller satellite asteroid in the video below.