Once again Richard Miles (Director of the BAA, asteroids and comets section) has been following up interesting activity on the periodic comet, Comet 29P/ Schwassmann-Wachmann. His report is below.
Comet 29P/ Schwassmann-Wachmann orbits in a relatively cool region of the solar system more than 6 AU from the sun and yet it is the most active periodic comet known. Normally comets become active as they approach a close perihelion where solar heating is important. For this comet the evidence suggests that carbon monoxide is the main driver of its outbursts. Amateur astronomers regularly monitor the comet looking for such outbursts. On January 20 Spanish amateur Faustino Garcia (J38) reported a small outburst of comet 29P. Four days earlier he had measured the comet at magnitude 16.6 but on the morning of the 20th it looked more like a star at magnitude 14.9, a surge in brightness of about a factor of 5 having taken place. The last time amateurs detected an outburst of 29P was in May 2010.
About one week after the latest outburst, it has been possible to take a deep image of the comet using the Faulkes Telescope North . By tracking the comet and adding together 21 CCD frames having a total integration time of 65 minutes, a high signal-to-noise image has been obtained enabling image analysis to look for features within the freshly-formed coma. Looking at these images (see box, right) it is clear that the expansion of the coma as been largely in a direction towards one hemisphere as can be seen in the grayscale log-stretched image. Rotational gradient processing using IRIS software has revealed delicate structures within the coma as illustrated in the false-color image alongside.
The seeing for Faulkes Telescope North was good (1.2 arcsec fwhm) and so it has also been possible to study the region close to the comet nucleus. The features shown in the inset show that the nucleus is still active having expelled more material within the last day or so. Early last year comet 29P underwent a much more energetic outburst. The comet is now well placed for observation and amateurs will be carefully monitoring the object in anticipation of a more marked outburst over the coming weeks.
Richard Miles
British Astronomical Association
