Cryovolcanic eruption on comet 29P/Schwassmann-Wachmann

Cryovolcanic comet 29P/Schwassmann-Wachmann suddenly brightened by more than 4 magnitudes on November 22, 2022, signaling a new significant eruption/outburst was underway. After the eruption, cryomagmatic debris started expanding in a shell shaped like Pac-Man.

Patrick Wiggins is to be congratulated for imaging Centaur comet 29P hours after the very intense outburst. The first measurement following the strong outburst showed the comet reached magnitude 11.95R, according to information provided by the British Astronomical Association (BAA).¹

The first close-up of the expanding outburst coma was made by André Debackère on November 23.

Notice the characteristic ‘Pac-Man’ shaped cut-out at position angles of 0° to 60°, which suggests that the direction of the outburst projected on the sky was in p.a. 210° approx.

Coma was expanding on November 24 but there were no signs of a further outburst.

Fine details in the expanding debris cloud started appearing on November 25 in the image captured by the Faulkes Telescope North and reproduced to the same image scale as the similar processed image on November 23.

Processing the data with a rotational gradient filter, Debackère found a bright plume of debris at a position angle of 330 degrees (the 1 o’clock position):

“This narrow plume probably leads back to the primary source the eruption,” Dr. Tony Phillips of the SpaceWeather noted.¹

Currently streaming away from the nucleus at 75 m/s (270 km/h), the plume stretches more than 11 000 km (6 835 miles) into space.

“If an eruption like this were happening on Earth, it would be plastering thousands of satellites with frosty hydrocarbons,” Phillips said.

“The integrated brightness of the comet (magnitude +11), puts it within easy reach of many backyard telescopes. Pac-Man already subtends an angle wider than Mars and, if past eruptions are any guide, it should grow much larger in the nights ahead. Observers can find 29P after sunset in the constellation Gemini.”

29P/Schwassmann-Wachmann is a member of a relatively new class of objects called Centaurs. It was discovered on November 15, 1927, by Arnold Schwassmann and Arno Arthur Wachmann at the Hamburg Observatory in Bergedorf, Germany.

The comet is unusual in that while normally hovering at around 16^th magnitude, it suddenly undergoes an outburst. This causes the comet to brighten by 1 to 5 magnitudes. This happens with a frequency of 7.3 outbursts per year, fading within a week or two.³

The magnitude of the comet has been known to vary from 18^th magnitude to 10^th magnitude, a more than a thousand-fold increase in brightness, during its brightest outbursts. These outbursts are very sudden, rising to the maximum in about 2 hours, which is indicative of their cryovolcanic origin; and with the times of outburst modulated by an underlying 57-day periodicity possibly suggesting that its large nucleus is an extremely slow rotator.⁴

References:

¹ MISSION 29P – Centaur comet observing campaign – British Astronomical Association – Accessed November 26, 2022

² Cryovolcanic eruption on a comet – SpaceWeather – November 26, 2022

³ Comet 29P/Schwassmann–Wachmann – WikiPedia – Accessed November 26, 2022

⁴ Discrete sources of cryovolcanism on the nucleus of Comet 29P/Schwassmann–Wachmann and their origin – Richard Miles – Science (2015) – https://doi.org/10.1016/j.icarus.2015.11.011

Featured image: Comet 29P/Schwassmann-Wachmann (Schwassmann-Wachmann 1) by Spitzer Space Telescope (SST). Credit: NASA/JPL/Caltech/Ames Research Center/University of Arizona (date of capture unknown)