A re-discovered asteroid with an estimated diameter between 53 and 120 m (174 - 394 feet), designated 2010 WC9, will flyby Earth at a distance of 0.53 LD / 0.00136 AU (203 453 km / 126 419 miles) on May 15, 2018. This is one of the closest flybys from an asteroid of this size.
This asteroid belongs to the Apollo group of asteroids. It was first observed on November 30, 2010 at the Mt. Lemmon Survey, a part of the Catalina Sky Survey in Arizona, US. However, the asteroid was lost shortly after its discovery and its orbit could not be accurately determined. It was re-discovered on May 8, 2018 when ZJ99C60 was detected as a close approach asteroid. Astronomers soon realized what they are looking at is actually long-lost WC9.
Its closest approach will take place at 22:05 UTC on May 15, at a speed (relative to the Earth) of 12.66 km/s, and its MPC "U" parameter, orbit uncertainty estimate, is 1 (with 0 being good and 9 being highly uncertain).
This is the 32nd known near-Earth asteroid to flyby Earth within 1 lunar distance since the start of the year and the first since 2018 HV of April 22, 2018.
The next close approach of this object will take place on October 17, 2019 at a distance of 111 LD / 0.286 AU. It won't come as close as it will on May 15 at least until 2200.
Featured image: The green line indicates the object's apparent motion relative to the Earth, and the bright green marks are the object's location at approximately one-hour intervals. The Moon's orbit is grey. The blue arrow points in the direction of Earth's motion and the yellow arrow points toward the Sun. Credit: Minor Planet Center.