Huge double asteroid to pass safely May 25 (earthsky.org)

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Posted by Eddie Irizarry in Space | May 23, 2019

Although it won’t be visible to the eye, professional and amateur astronomers are watching for asteroid 1999 KW4. It’s oddly shaped, about a mile wide, with a companion moon. Closest approach is May 25, 2019. Charts here for amateur observers across the globe.

A large double asteroid is now approaching Earth’s vicinity and will pass by Earth safely on May 25, 2019. Closest approach is at 23:05 UTC (7:05 p.m. EDT; translate UTC to your time) on May 25. Asteroid (66391) 1999 KW4 consists of a primary space rock just under a mile wide (about 1.5 km), with a 0.3-mile-wide (0.5-km-wide) companion asteroid – an asteroid moon – orbiting the main asteroid. Although not visible to the eye alone, the asteroid and its moon will provide a good opportunity for both professional and amateur astronomers to observe the huge space rock. Amateur astronomers will be able to observe it for a few days around May 25. See the charts provided at the bottom of this post.

The video above – from a NASA Goldstone Radar planning document – shows the orbital motion of 1999 KW4 from December 2017 until July 2019, in a heliocentric or sun-centered reference frame. The asteroid makes two close flybys of Earth during this period.

1999 KW4 is an Aten type – or Earth-crossing – space rock. Its orbit brings it between the orbits of Venus and Earth. It completes an orbit around the sun once every 6.18 months (188 days).

During the approach of May 25, 2019, the asteroid will pass at the very safe distance of 3,219,955 miles from Earth (5,182,015 km), or about 13.5 times the Earth-moon distance.
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more (incl. lots of links): https://earthsky.org/space/double-asteroid-1999-kw4-closest-may-25-2019