Asteroid 2010 WC9 will safely pass at about half’s the moon’s distance on Tuesday, May 15, 2018.
Estimates of its size range from 197 to 427 feet (60-130 meters), making the May 15 pass one of the closest approaches ever observed of an asteroid of this size.
This asteroid was “lost” and then found again. The Catalina Sky Survey in Arizona first detected it on November 30, 2010, and astronomers watched it until December 1, when it became too faint to see. They didn’t have enough observations to track its orbit fully and so predict its return.
On May 8, 2018 – almost eight years later – astronomers discovered an asteroid and gave it the temporary designation ZJ99C60. Then they realized it was asteroid 2010 WC9, returning.
During the 2018 return, closest approach of asteroid 2010 WC9 will happen on May 15 at 22:05 UTC (6:05 pm EDT; translate to your time). At that time, the asteroid will be 0.53 lunar-distances from Earth (126,419 miles or 203,453 km from Earth). According to orbit calculations made by NASA’s Jet Propulsion Laboratory, the May 15 close approach is the closest of this particular asteroid in nearly 300 years.
Is this a large asteroid? No, not by any absolute measure. But it is larger than the estimated size of the Chelyabinsk meteor, which entered Earth’s atmosphere, breaking windows in six Russian cities and causing some 1,500 people to seek medical attention, in 2013. Estimates of asteroid 2010 WC9’s diameter ranges from 197 to 427 feet (60-130 meters); estimates of the Chelyabinsk meteor’s size before encountering Earth’s atmosphere center around 65 feet (20 meters).
Asteroid 2010 WC9 is an Apollo type space rock. At no time will it be visible to the eye as it sweeps past Earth. It might get as bright as magnitude +11, which would make it bright enough to be seen in amateur telescopes pointed at the correct location and time.
Asteroid 2010 WC9 is travelling through space at a speed of 28,655 miles per hour (46,116 km/h).
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