Comet Garradd and M71

A few years ago, while cruising idly along the background of the Milky Way, the faint Comet Garradd paid a visit to the pretty little globular star cluster M71 in Sagitta. I took a number of 4-minute exposures to make a brief time lapse movie, and the comet moved perceptibly between each frame. Its blue-green coma and tail results from the fluorescence of the gas cyanogen.

The next image shows how far the comet moved in just one day.

Image copyright by Joe Bergeron.