A small chunk of rock measuring just under four meters (13 feet) across appears to orbit Comet 67P in a short GIF put together by astrophotographer Jacint Roger.
Roger first noticed the piece of orbital debris back in May. This week, the ESA talked a bit more about the Comet 67P’s little companion. The chunk of rock is seen following along the comet during its closest approach to the Sun (or perihelion) back in October 2015.
The ESA dives into more detail:
Modelling of the Rosetta images indicates that this object spent the first 12 hours after its ejection in an orbital path around 67P/C-G at a distance of between 2.4 and 3.9 km from the comet’s centre. Afterwards, the chunk crossed a portion of the coma, which appears very bright in the images, making it difficult to follow its path precisely; however, later observations on the opposite side of the coma confirm a detection consistent with the orbit of the chunk, providing an indication of its motion around the comet until 23 October 2015.
The outgassing seen in the GIF above is the likely culprit for creating this mini-moon. As comets reach the closest point to the Sun in their orbits, they often light up as gas and dust streams from their surface due to the Sun’s heat. This outgassing can be violent enough to cause small eruptions that toss debris into space. In this case, it’s the biggest chunk seen so far as scientists and amateur astronomers pour over the images.
But this little ‘Churymoon,’ as ESA research Julia Marín-Yaseli de la Parra calls them, isn’t that out of the ordinary. The Rosetta team analyzed hundreds of pieces of the comet circling it after being ejected from the surface. The sizes ranged from small grains to chunks two meters across. Roger’s discovery does make it the biggest one, however. And researchers plan to study the little ‘Churymoon’ further as they continue to go over all the data Rosetta collected on Comet 67P during its two-year stay around the comet.
We’re coming up on the three-year anniversary of the end of Rosetta’s mission around Comet 67P. The spacecraft touched down on the comet’s surface at a gentle one mile per hour. It snapped this final image 51 meters (167 feet) above the surface.
Three years later and we’re still learning more about Comet 67P and the environment around it.