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New observations from three of the largest radio telescopes in the world have revealed something new about an asteroid with a big name: 2017 YE5. This object, which was swept by the Earth at the end of June 2018, is actually made of two bodies orbiting a common center of gravity. Each little world has a height of about 900 meters. Radar observations show that these space rocks have similar sizes, but indicate that the two objects can be very different in terms of composition and density. In fact, astronomers from NASA suggest that one or both rocks could be comets of the Jupiter family.
The Arecibo Observatory in Puerto Rico, as well as the Goldstone solar system radar in California and the Green Bank observatory in West Virginia combine their efforts. to study this object as it swept the closest to us in June. Studies have shown not one, but two objects, roughly equal in mass. It is only the fourth binary asteroid of equal mass near the Earth never detected.
In addition, recent studies have revealed that the two tiny worlds of the 2017 YES system articulate with each other once every 20 to 24 hours. And they showed that objects do not reflect as much sunlight as a typical rocky asteroid. In fact, the scientists said, 2017 YE5 is probably as dark as charcoal.
Artist's illustration of the trajectory of the 2017 YE5 asteroid through the solar system. At its closest approach to Earth, the asteroid arrived at 16 times the distance between the Earth and the Moon. Image via NASA / JPL-Caltech
Astronomers from Morocco Oukaimeden Sky Survey (MOSS) discovered the near-Earth asteroid 2017 YE5 on December 21, 2017. But the object did not not been closest to us until June. 21, 2018. The near approach to June was the closest that this little system will come to Earth for at least the next 170 years, or about 15.5 lunar distances (within 3.7 million miles, or 6 million km). The approach was close enough to provide a good opportunity for radar observations, and even for optical observations, as the asteroid was reaching a visual magnitude of 15.
Scientists estimate that among asteroids close to Earth larger than 200 meters in size, about 15 percent are binaries with a larger object and a much smaller satellite. The equal mass binaries like 2017 YE5 are much rarer.
The contact binaries – where two objects of similar size actually touch each other – account for 15% of Earth's asteroids larger than 200 meters.
Bi -Static radar images of the 2017 YE5 binary asteroid of the Arecibo Observatory and the Green Bank observatory on 25 June. The observations show that the asteroid is made up of two separate objects orbiting one of the other. Image by Arecibo / GBO / NSF / NASA / JPL-Caltech
Three of the largest observatories in the world have come together to make the discovery, according to a NASA / JPL statement:
June 21 and 22 The observations of NASA's Solar System Goldstone Solar System (GSSR) 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. Eventually, both objects turned to expose a separate gap 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 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 independently 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 Center for Solar System Studies at 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 reflectivity differences 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. [19659017] Radar images of the 2017 NASA Goldstone Solar System Radar (YSS) binary asteroid (GSSR) The observations, made on June 23, 2018, show two lobes, but do not show two separate objects yet. GSSR / NASA / JPL-Caltech
Conclusion: The 2017 YE5 asteroid, which was swept by the Earth at the end of June 2018, was observed as as a binary asteroid close to Earth. never detected,
Via NASA / JPL
