An Earth mini-me of sorts will zip past us this weekend at a safe 3 million miles away that gives astronomers a chance to study and prepare for an actual potential hit.
The impending visit of 1999 KW4, as the mile-wide asteroid with moon in tow is known, will not be visible to the naked eye. But astronomers are gearing up to gather oodles of data from this binary system using telescopes, radar and all manner of sensitive instruments and implements.
“Attracted by our star’s gravitational pull, it will pass five million km [about 3.2 million miles] above our heads — about 13 times further than the moon — and dozens of telescopes around the globe will use this opportunity to collect as much information as they can about its size, shape and composition,” explains the European Space Agency, one of the numerous organizations tracking the twirling twosome.
From May 29 through June 7, radar observations will be conducted from the Arecibo Observatory in Puerto Rico, and from May 26 through 31 it will be observed with the Goldstone Solar System Radar in California, according to Earthsky.org.
“It's one of the closest binary flybys probably in recent history,” Vishnu Reddy, a planetary scientist at the University of Arizona in Tucson, told NBC News. “That’s what makes it a very interesting target.”
The asteroid was discovered in 1999 by the Lincoln Near-Earth Asteroid Research (LINEAR) astronomical survey in Socorro, New Mexico. While it is technically classified as a Near-Earth object and a potentially hazardous object, it never comes closer than five Earth-moon distances, notes Earthsky.org.
While it’s just 0.8 miles in diameter, it’s “actually quite a complex shape,” says Las Cumbres Observatory, a global telescopic network. “It is 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 similar to a walnut or a spinning top.”
The “moon” is about a third of a mile across, and they orbit one another every 17.5 hours, about 1.6 miles apart, Las Cumbres said, adding that radar images reveal the main asteroid to be “a rocky ‘rubble pile,’ though with a density much lower than that of typical rocks on Earth.
It orbits the sun every 188 days, or a little over six months, according to ESA.
This is the largest space rock scheduled to get this close to our planet for another eight years, Earthsky.org says. The next one is Asteroid 4953 (1990 MU), which will cruise by in 2027 at 12 Earth-moon distances, returning in 2058 at nine lunar distances.
Part of the intense interest stems from the need to prepare for something that could actually hit Earth, Las Cumbres said.