How a Comet Sneezes Dust express
In the summer of 2021, comet 7P/Pons-Winnecke put on quite a show. A network of telescopes, the Las Cumbres Observatory, tracked it for nearly three months and counted eight sudden outbursts. Each outburst is like a lid popping off the surface: a cloud of dust and gas blasts into space, and the comet briefly brightens.
The strength of these outbursts varied — from barely noticeable to ones that immediately caught the eye. The mass of ejected material each time ranged from 100,000 to 1,000,000 kilograms. That's roughly equivalent to a hundred cars turned into dust in an instant. The shapes of the ejecta also differed, hinting that the comet 'sneezed' from different parts of its surface.
When scientists compared the outburst frequency of 7P with other comets, they got a surprise. After accounting for nucleus size, this comet behaved similarly to 41P, 9P, and 46P — about one outburst per unit area over a given time. But with comet 67P, which the Rosetta probe studied in detail, there was a discrepancy. Ground-based telescopes saw ten times fewer outbursts than the spacecraft, which was right next to it. This means we simply miss many small events from Earth, and the true lives of comets are much more turbulent.
Original abstract
as written by the authors arXiv:2606.25070
Cometary outbursts may be used as a means to infer the physical processes occurring on cometary nuclei. To that end, we studied eight outbursts of comet 7P/Pons-Winnecke identified between 2021 June 3 and 2021 August 31. The data analyzed consisted of optical images and derived photometry of the comet from the Las Cumbres Observatory network of telescopes. The outburst strengths relative to the ambient coma ranged from -0.2 to -1.1 mag, and the ejecta themselves had apparent brightnesses ranging from 17.4 to 13.3 mag. The morphologies of the ejecta varied, suggesting that the events may have originated from different sources across the nucleus. An order of magnitude estimation of the ejecta masses ranged from 10$$^{5}$$ - 10$$^{6}$$ kg, similar to other mini-outbursts of comets. The surface-area normalized outburst rate estimated during this time period is similar to comets 41P/Tuttle-Giacobini-Kres\'ak, 9P/Tempel 1 and 46P/Wirtanen, but 10 times larger than that observed at comet 49P/Arend-Rigaux. However, a comparison to the mini-outburst rate of comet 67P/Churyumov-Gerasimenko reveals significant discrepancies between Rosetta spacecraft results and those from ground-based telescopes. We also investigate whether or not cometary outbursts from 7P in the 19th century are needed to explain outbursts in meteor shower rates observed in the 20th century.
Comet outbursts can be so faint that they are only noticed when comparing images taken minutes apart, like looking for a missing sock in a pile of similar ones.
In Arthur C. Clarke's novel 'Rendezvous with Rama,' humans investigate an object that suddenly begins to show activity — what's that if not a giant comet outburst?