May 23, 2019– Mary Greeley News – An asteroid nearly a mile wide with a moon of its own is expected to pass by Earth this weekend, traveling at 48,000 mph. The space rock, known as asteroid 1999 KW4, was discovered 20 years ago and is so large that it is orbited by a moon.
On Saturday evening, 1999 KW4 will make its closest approach to Earth. It will be visible until May 27. Because it carries a large moon along with it, the asteroid is technically designated as a binary system.
A binary system is defined as two celestial objects close enough to orbit each other, according to NASA.
Asteroid 1999 KW4 is designated a double asteroid or a binary asteroid. Its companion rock is 0.3-miles wide and orbits around the larger body about once every 16 hours.
The Las Cumbres Observatory describes 1999 KW4 as “slightly squashed at the poles and with a mountain ridge around the equator, which runs all the way around the asteroid. This ridge gives the primary an appearance like a walnut or a spinning top.”
1999 KW4 was discovered by the Lincoln Near-Earth Asteroid Research (LINEAR) astronomical survey in Socorro, New Mexico, in 1999. It has been classified as a Near-Earth object and a potentially hazardous object by the Minor Planet Center.
However, the orbit of this huge space rock is well understood and known to pose no risk to Earth. During the closest of its approaches to Earth, its orbit brings it no closer than five Earth-moon distances.
An interesting fact: After asteroid 1999 KW4 passes by Earth on May 25, 2019, no known asteroid as big or larger than this space rock will approach our planet this close until year 2027. On June 6, 2027, asteroid 4953 (1990 MU), a 4 km to 9 km (2.5 to 5.5 mi) space rock will safety pass by Earth at 12 lunar distances, and will return on 2058 at nine lunar distances.
The closest approach will happen Saturday at 7:05 p.m. EDT, according to EarthSky. The bad news for people in the U.S. is that it will be best viewed from the southern hemisphere. The good news is people in the northern hemisphere should be able to see it two days later — but you will need a telescope at least eight inches in diameter, according to EarthSky.
credit: In part with https://www.cbsnews.com/news/asteroid-kw4-1999-this-week-a-massive-asteroid-with-its-own-moon-orbiting-it-will-pass-by-earth-nasa-reports/