29P Outburst January 14, 2021

Francois Kugel and J. F. Soulier posted before and after images and observations of an outburst of 29P/Schwassmann-Wachmann that occurred on January 14, 2021.

The object’s brightness was at magnitude 17.3 on the night before the outburst on 2021-Jan-13.7 UT. Brightness increased to magnitude 14.9 one night later on 2021- Jan-14.7 UT or by about 2.4 magnitudes. Nuclear magnitude plots for 29P show the characteristic decline in brightness following an outburst. J. F. Soulier’s image of 2021-Jan 18.7 UT shows a typical expansion disk.

The French lesia web site has a nice online feature for plotting magnitudes for each comet in their database. The following plot generated using their web pages covers a portion of the timeline back a year and a half. The January 14, 2021 outburst was smaller than the outbursts that occurred in 2020.

Outbursts from 29P typically occur several times per year just as it has since its 1927 discovery by Arnold Schwassmann and Arno Arthur Wachmann at the Hamburg Observatory in Hamburg, Germany.

29P is a fun object to observe.


Many professional observers have studied 29P through the decades.
Elizabeth Roemer and Fred Whipple have written dozens of papers on 29P.
29P has been observed with both the Hubble and Spitzer Space Telescopes.
The coma typically develops an expansion shell that grows asymmetrically in size with time with expansion velocity near 0.13 km/s.

The orbit of 29P is of low eccentricity or nearly circular such that heliocentric distance or time from perihelion does not seem to correlate to frequency of outbursts. There are several theories on the outburst mechanism and several estimates of its rotational period.

Published by Charles Bell

The observer at MPC Observatory H47 near Vicksburg, Mississippi, USA

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