NPR Blogs

LOOK! The Asteroid That Flew Past Earth Tuesday Has Its Own Moon

By Eyder Peralta

Published January 27, 2015 at 8:01 AM EST

In celestial terms, asteroid 2004 BL86 pretty much buzzed Earth, coming within 745,000 miles of our planet.

As NPR's Sam Sanders explained, it's the closest this asteroid will pass by Earth for at least the next two centuries. So when it flew by yesterday, scientists trained their instruments on it.

Scientists using the Deep Space Network antenna at Goldstone, Calif., captured a stunning set of images that revealed 2004 BL86 has a small moon.

Take a look:

NASA's Jet Propulsion Laboratory explains this phenomenon is actually pretty common:

"The 20 individual images used in the movie were generated from data collected at Goldstone on Jan. 26, 2015. They show the primary body is approximately 1,100 feet (325 meters) across and has a small moon approximately 230 feet (70 meters) across. In the near-Earth population, about 16 percent of asteroids that are about 655 feet (200 meters) or larger are a binary (the primary asteroid with a smaller asteroid moon orbiting it) or even triple systems (two moons). The resolution on the radar images is 13 feet (4 meters) per pixel."

Corrected: January 27, 2015 at 12:00 AM EST

An earlier version of this post incorrectly said Monday's flyby is the closest a known asteroid of this size will pass by Earth in at least the next two centuries. In fact, it's the closest this particular asteroid will pass by Earth in that time; another asteroid of similar size is expected in 2027.