Fly-by asteroid found to have its own moon

Radar telescopes found a secondary body in orbit around the near-Earth object 2004 BL86

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The asteroid was tracked by several radar telescopes around the world


An asteroid that flew closely past the Earth has its own moon. Images of asteroid 2004 BL86 taken by NASA’s Deep Space Network antenna at Goldstone show another body orbiting around the asteroid.

On 26 January 2015, BL86 flew past the Earth at a distance of only 1.2 million km, the closest pass an asteroid this size will make until 2027. As well as thousands of amateurs, several professional telescopes were trained on the object, using this unique opportunity to study the object. The data collected managed to pin down the size of BL86 to 325m, but also revealed that it had another body orbiting around it that was 70m across.

Around 16 per cent of near-Earth asteroids larger than 200m have a secondary, smaller asteroid orbiting around them, and several even have two. Radar is a powerful tool in asteroid characterisation as it lets scientists study the size, shape, rotation and surface of the asteroid without having to send a mission to orbit the asteroid. This close pass allowed astronomers to resolve down to 4m per pixel, revealing BL86's small companion.

The studies also helped to pinpoint the trajectory of the asteroid to an even greater accuracy than it had been known previously, allowing its path to be predicted further into the future. NASA and other space agencies place a high priority on tracking asteroids as an early warning system for any that might potentially hit the Earth and cause significant damage.

It’s believed that over 98 per cent of near-Earth objects have been found and are being tracked in their journey through the heavens. Currently there is no way to deflect a hazardous asteroid, though NASA plans to launch OSIRIS-REx mission in 2016 to one of the most worrisome asteroids known, (101955) Bennu. This will serve as a path finder for future missions aiming to study and deflect Earth bound asteroids.


 

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