Asteroid that flew close to Earth has its own moon

The asteroid that zipped past Earth on January 26th has its own small moon, according to radar images taken from NASA’s 230-foot-wide Deep Space Network antenna at Goldstone, California.

Asteroid 2004 BL86 flew past Earth yesterday at a distance of 745,000 miles (1.2m km), which is about 3.1 times as far as from here to the Moon.

The twenty individual pictures were generated from data gathered at Goldstone on January 26th, 2015. They show that the main body of the asteroid is about 325 metres (1,100 feet) across, while its small moon is approximately 70 metres (655 feet) across.

Asteroid 2004 BL86

Image showing asteroid 2004 BL86 and its small moon above it (Image: NASA Jet Propulsion Laboratory).

About 16% of asteroids in the near-Earth population that are at least 200 metres (655 feet) across have a smaller asteroid moon. Many have two moons.

Asteroid 2004 BL86’s approach to Earth was the closest it will make for at least two hundred years. In 2027, asteroid 199 AN10 will do a similar-distanced flyby. This asteroid was discovered in 2004 by the Lincoln Near-Earth Asteroid Research (LINEAR) survey in White Sands, New Mexico.


Radar is a powerful method for studying an asteroid’s surface features, size, shape, rotation state and surface roughness. It also helps improve the calculation of its orbits. Radar measurements help scientists predict asteroid orbits far into the future.

NASA said in a statement on Monday:

“NASA places a high priority on tracking asteroids and protecting our home planet from them. In fact, the U.S. has the most robust and productive survey and detection program for discovering near-Earth objects (NEOs). To date, U.S. assets have discovered over 98 percent of the known NEOs.”

NASA plans to launch a robotic probe next year to one of the most potentially hazardous of the known NEOs. The OSIRIS-REx mission to asteroid (101955) Bennu will map the path for future spacecraft designed to perform reconnaissance on any objects that may pose a threat to our planet.

NASA does not only study asteroids and comets because of their potential threats. They provide useful data on the origins of our solar system, where water on Earth came from, and even the origin of life-developing organic molecules.

Video – Asteroid 2004 BL86 Has a Small Moon

This ‘movie’ of the asteroid was generated from radar data gathered on 26th January, 2015, by NASA’s Deep Space Network antenna. Twenty images were used.