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New observations by three of the largest radio telescopes in the world revealed that one asteroid discovered last year is actually two objects, each of about 900 meters, orbiting around the world. # 39; other.
The near-Earth asteroid 2017 YE5 was discovered with observations provided by the Morocco Oukaimeden Sky Survey on December 21, 2017, but no detail on the physical properties of the asteroid was known until the end of June. This is only the fourth asteroid close to the binary Earth "equal mass" never detected, consisting of two objects of almost identical size, orbiting one with respect to the other. The new observations provide the most detailed images ever obtained from this type of binary asteroid.
On June 21, the 2017 YE5 asteroid made its closest approach to the Earth for at least the next 170 years, reaching 3.7 million miles (6 million kilometers) from the Earth, either about 16 times the distance between the Earth and the Moon. On June 21st and 22nd, NASA's Goldstone Solar System Radar (GSSR) observations in California showed early signs that 2017 YE5 could be a binary system. The observations revealed two distinct lobes, but the orientation of the asteroid was such that scientists could not see if the two bodies were separated or joined. Finally, both objects turned to expose a separate space between them.
Scientists at the Arecibo Observatory in Puerto Rico had already planned to observe 2017 YE5, and they were alerted by their colleagues at Goldstone to the unique properties of the # 39; asteroid. On June 24, scientists teamed up with researchers from the Green Bank Observatory (GBO) in West Virginia and used the two observatories together in a bi-static radar configuration (in which Arecibo transmits the radar signal and Green Bank receives the signal back) . Together, they were able to confirm that 2017 YE5 consists of two separate objects. On June 26, Goldstone and Arecibo both confirmed the binary nature of the asteroid
. New observations obtained between June 21 and June 26 indicate that the two objects rotate around each other every 20 to 24 hours. This was confirmed by observations of visible light changes in brightness by Brian Warner at the Solar System Studies Center in Rancho Cucamonga, California
The radar imaging shows that both objects are larger than their brightness two rocks do not reflect as much sunlight as a typical rocky asteroid. 2017 YE5 is probably as dark as charcoal. Goldstone's images taken on June 21 also show a striking difference in the radar reflectivity of the two objects, a phenomenon that had not been observed previously among more than 50 other binary asteroid systems studied by radar since 2000. (However, the majority of these binary asteroids The differences in reflectivity also appear in the Arecibo images and suggest that the two objects may have different densities, compositions close to their surfaces or different surface roughness [19659010Doubleasteroid”/>
Scientists estimate that of the near-Earth asteroids larger than 200 meters, nearly 15 percent are binaries with a larger object and a much smaller satellite. The equal mass binaries like 2017 YE5 are much rarer. Contact binaries, in which two objects of similar size are in contact, would constitute another 15% of the asteroids close to the Earth whose size is greater than 200 meters.
The discovery of the 2017 YE5 binary nature provides scientists with an important opportunity to improve understanding of different types of binaries and to study the training mechanisms between binaries and contact binaries, that can be linked. The analysis of combined radar and optical observations could allow scientists to estimate the densities of YE5 2017 objects, which will help to better understand their composition and internal structure, as well as their formation
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