It took three of the world’s largest radio telescopes to get a better picture of what the YE5 asteroid looked like, but when NASA finally caught a glimpse of the planetoid, the agency was shocked. While working to improve NASA’s asteroid detection and tracking capabilities, scientists discovered that YE5 is a double asteroid, a rare instance of two equal-mass objects orbiting each other.

The near-Earth asteroid was first discovered by the Morocco Oukaimeden Sky Survey in late 2017, but its properties remained a mystery for months. On June 21, YE5 came within 3.7 million miles of Earth, giving scientists an opportunity to get up close and personal with the asteroid. It was then that NASA’s Goldstone Solar System Radar (GSSR) first learned YE5 was a binary asteroid, making it the fourth equal-mass binary near-Earth asteroid ever detected. NASA released the rare footage of the phenomenon on Thursday.

Artist's concept of what binary asteroid 2017 YE5 might look like. The two objects showed striking differences in radar reflectivity, which could indicate that they have different surface properties.
Artist's concept of what binary asteroid 2017 YE5 might look like. The two objects showed striking differences in radar reflectivity, which could indicate that they have different surface properties.

To collect images of the binary asteroid, NASA scientists at the GSSR teamed up with the Arecibo Observatory in Puerto Rico and researchers at the Green Bank Observatory (GBO) in West Virginia. These two observatories were able to create a bi-static radar configuration in which Arecibo transmits the radar signal and Green Bank receives the return signal.

Initially, these observations revealed two distinct lobes that appeared to be joined. It wasn’t until a later rotation that scientists could identify a gap between them. By June 26, both Goldstone and Arecibo had independently confirmed that YE5 does consist of two separate objects that revolve around each other every 20 to 24 hours.

Scientists estimate that among near-Earth asteroids larger than 650 feet, about 15 percent are binaries with one larger object and a much smaller satellite. However, equal-mass binaries like YE5 are much rarer, as this is only the fourth scientists have been able to document. It might be awhile before NASA can collect more details on YE5’s physical attributes, seeing as it won’t come within that close proximity to Earth again for another 170 years.

Footage from this brief encounter with YE5 is not only rare but important for scientists to better understand binary systems and their formations. In the short span of time that YE5 came within 3.7 million miles of Earth, NASA was able to collect radar and optical observations to estimate both densities in the double asteroid, giving scientists clues to its internal structure and earliest formation. YE5’s binary nature was more than a surprise to scientists, but a game changer for how scientists will investigate double asteroids.