Comet Holmes Becomes Visible

An obscure periodic comet -- Comet Holmes, designated 17P, suddenly brightened by about a factor of one million starting on Wednesday morning, October 24. From about magnitude 18, so dim that only a large telescope at an observatory would be able to detect it, the comet brightened within hours to magnitude 3, visible with the naked eye, even in the skyglow of a major city like Yokohama -- or Toronto, if the cloud cover would just go away.

A constellation schematic of Perseus and a telescopic finder chart are avilable for observers.

P17/Holmes currently has the appearance of a bright yellow star in the constellation Perseus, comparable in apparent brightness to the other major stars in that grouping. The unusual brightening was probably due to material outgassed from the comet nucleus -- very strange given that perihelion passage (closest approach to the sun) happened a few months ago, and the comet is heading back outwards. The comet itself is part of the Jupiter family of comets -- its perihelion falls outside the Earth's orbit, 2.2 AU from the sun. Its aphelion point is way out around the orbit of Jupiter.

In three of my most favourite places -- northern BC, Lake Herridge in northern Ontario, or rural Newfoundland -- the comet should be quite visible under near ideal conditions -- at least if the sky were cloud free. Clouds in fall/winter are definitely a problem. The advent of Comet McNaught back in January was a complete non-starter for us here -- every night that McNaught would have been visible was a night where it was cloudy in Toronto. But hopefully, we will have better luck with P17/Holmes.