Rare asteroid binary discovered in near-Earth orbit

Researchers just discovered a rare asteroid binary, 2017 YE5, in near-Earth orbit.
By Tyler MacDonald | Jul 18, 2018
Scientists recently discovered a rare asteroid binary,2017 YE5, in near-Earth orbit. The finding marks the closest that YE5 has been to Earth in 170 years, and gives researchers a unique look into the rare occurrence.

The team discovered the contact binary using the resources of multiple observatories, including Arecibo, Goldstone, and Green Bank. And analysis of the data revealed the reason that the objects rotate around each other in a stable configuration: the barycenter, which is the center of mass in the two-body system, is in between the two asteroids.

Interestingly, the observations reveal differences in the way the two asteroids reflect radar.

"The Goldstone images taken on June 21 also show a striking difference in the radar reflectivity of the two objects, a phenomenon not seen previously among more than 50 other binary asteroid systems studied by radar since 2000 (however, the majority of those binary asteroids consist of one large object and a much smaller satellite.)" NASA's Jet Propulsion Laboratory said in a statement.

"The reflectivity differences also appear in the Arecibo images and hint that the two objects may have different densities, compositions near their surfaces, or different surface roughnesses."

"Scientists estimate that among near-Earth asteroids larger than 650 feet (200 meters) in size, about 15 percent are binaries with one larger object and a much smaller satellite," the statement continued. "Equal-mass binaries like 2017 YE5 are much rarer. Contact binaries, in which two similarly sized objects are in contact, are thought to make up another 15 percent of near-Earth asteroids larger than 650 feet (200 meters) in size."


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