Satellite Discovered in Churyumov-Gerasimenko Comet Orbit

Photographs of comet 67P / Churyumov-Gerasimenko (67P/CG), taken by the OSIRIS camera on board the European Space Agency (ESA) Rosetta spacecraft, show an object with a diameter of about 4 meters, which probably burst out from the ice comet surface and remained in its orbit until at least October 23, 2015

The images collected for a couple of months after the comet was closest to the Sun along its orbit or perihelion (the closest point to the Sun) uncover an unusual satellite in the comet’s orbit – a piece of the orbital debris that scientists named Churymoon. At that time, Rosetta was more than 400 km away from the comet center.

The analysis of images, obtained on October21, 2015, shows that the object was at a distance of 2.4 to 3.9 kilometers from the center of the comet for the first 12 hours after the assumed escape from the surface of 67P / C-G. Then it crossed the part of the coma (the comet tail), very bright in the images, which makes it difficult to follow its exact track, and disappeared from sight. However, in later images, the object reappears, but already on the opposite side of the comet's tail, and is tracked until October 23, 2015.

Churymoon was discovered by astrophotographer Jacint Roger from Spain, who used and processed the Rosetta archive data and Twittered the final images.

Scientists have studied and tracked the debris around  67P / C-G Comet since the arrival of Rosetta in 2014. In their opinion, the object in these images is probably the largest of all previously discovered around the comet, and will be the subject of further research.

Last week, it was years since Rosetta arrived at its target, Comet 67P / C-G. And today it is exactly four years since the comet, accompanied by the spacecraft, reached its perihelion. The Rosetta mission ended on September 30, 2016, with a deliberate collision of the device with a comet.

Comet 67P / C-G is currently in the outer Solar system, between the orbits of Mars and Jupiter. It is expected to reach the Sun at the end of 2021.

Anastasia Sinitskaya