Near-Earth asteroid’s moon revealed

NASA has released the first radar images of an asteroid that made its closest pass of Earth yesterday at a distance of 1.2 million kilometres, revealing it has its own tiny moon.

The images were taken by NASA’s 70-metre Deep Space Network antenna at Goldstone, California.

The 20 individual images, put together to create the movie above, show the primary body, asteroid 2004 BL86, is approximately 325 metres in diameter and has a small moon approximately 70 metres across. Its closest approach was three times further away than our own Moon.

In the near-Earth population, about 16% of asteroids that are about 200 metres or larger are a binary (the primary asteroid with a smaller asteroid moon orbiting it) or even triple systems (two moons).

The trajectory of asteroid 2004 BL86 is well understood. Monday’s flyby was the closest approach the asteroid will make to Earth for at least the next two centuries. It is also the closest a known asteroid this size will come to Earth until asteroid 1999 AN10 flies past our planet in 2027.

Asteroid 2004 BL86 was discovered on 30 January 2004, by the Lincoln Near-Earth Asteroid Research (LINEAR) survey in White Sands, New Mexico.

NASA places a high priority on tracking asteroids and protecting Earth from them. A group of eminent scientists recently called for increased vigilance, saying that Earth was “living on borrowed time” with respect to a possible asteroid strike.

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