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Comet 29P/Schwassmann-Wachmann, 24 January 2008 - 03 January 2009

Arnold Schwassmann and Arno Arthur Wachmann discovered Comet 29P/Schwassmann-Wachmann on photographs exposed on 15 November 1927. (It was the first of several comets discovered by the pair and, below, for short is referred to as SW1.) It is unique in that it experiences one or more outbursts in brightness nearly every year. The comet is usually visible near magnitude 17 at perihelion and magnitude 19 at aphelion, but the outbursts can cause it to reach magnitude 13 and, on rare occasions, it has even reached magnitude 10. The orbit of SW1 is nearly circular and lies just outside the orbit of Jupiter. It has been stabilising since its discovery, with the initial eccentricity being 0.15 and the present being 0.04. During the same time the orbital period has declined from 16.0 years to 14.9.

I imaged SW1 during the period 24 January 2008 - 03 January 2009. The images are below; North is up in all cases.

20080124_29P_MJH.jpg 24 January 2008.

20080127_29P_MJH.jpg 24 & 27 January 2008.

20080204_29P_MJH.jpg 04 February 2008.

20081009_29P_MJH.jpg 09 October 2008.

20090103_29P_MJH.jpg 03 January 2009.

Postcript, November 2019

After 2009, the comet gradually moved into the southern sky out of range of my telescope. By late 2019 it had moved north again and is currently in Pisces, just 4.5° south-east of γ Pegasi, so is well placed in the south for observation as darkness falls. It will be well placed for northern hemisphere observers for many years to come. Reference [1] has maps of its track (from 2012 to 2027) and orbital elements for planetarium programs.

Richard Miles of the BAA has studied 29P extensively over many years and regularly takes images with the Las Cumbres Observatory (LCO) network [2]. All images from the network are freely available to download and process as long as LCO is credited if the results are used in publications.

Jonathan Shanklin has written an article in the December 2019 JBAA [3] providing a summary of comets, visible in 2020, of interest to amateurs. The article also shows a nice sequence of images by Damian Peach of 29P in outburst.



Seiichi Yoshida's comet web site has orbital elements and maps for all observable comets. The page for 29P is at http://www.aerith.net/comet/catalog/0029P/2019.html.


Las Cumbres Observatory web page: https://observe.lco.global/. To search for images of the comet use the "filter list" option with "username" as "richard_miles" or enter "29P" in the "Name Contains" field.


J. Shanklin, "Comet prospects for 2020", JBAA vol. 129, no. 6, pp.362-363.

Mike Harlow