Scientists have been looking for evidence of a bow shock around Comet 67p/Churyumov-Gerasimenko, the so-called Rubber Ducky comet that was probed by the European Space Agency in 2016. The comet got its name from its shape, which resembles a children’s rubber duck toy, and is believed to have arisen from a long-ago collision of two separate slow-moving comets.
A bow shock is created when the comet’s magnetic field meets the stellar wind and other energized particles in space. Initially, the ESA probe, Rosetta, did not find a bow shock around 67p.
In a new paper published in the Journal of Astronomy & Astrophysics, scientists now say that 67p did have a bow shock, but it was asymmetrical and faint, and moved in unexpected ways, which is why it was initially missed.
"We looked for a classical bow shock in the kind of area we'd expect to find one, far away from the comet's nucleus, but didn't find any, so we originally reached the conclusion that Rosetta had failed to spot any kind of shock," said Herbert Gunell of the Royal Belgian Institute for Space Aeronomy and Umeå University in Sweden, a co-author on the paper.
The astrophysicists conducted a more detailed analysis and found that the Rosetta probe passed through the magnetic region twice – once when the comet began its closest approach to the sun, and another time when the comet moved away from the sun.
"Rosetta observed a cometary bow shock in its infancy, a stage in its development not previously accessible,” the researchers wrote in their article, which also shows that Rosetta’s data included previously unseen sights: a bow shock in its nascence and its very last moments before death.
Photo credit: ESA