Online Astronomy eText: Asteroids, Comets, and Interplanetary Debris
Periodic Comet P17/Holmes
(October 2007 finding chart and placeholder)
Page last updated Mar 12, 2022
Finding chart for Comet P17/Holmes (
 In late October 2007, Comet Holmes (periodic comet 17) underwent a remarkable brightening, from 17th magnitude to 2nd magnitude, a million-fold increase in brightness which took it from total invisibility even with large telescopes in the bright skies in Long Beach, to naked-eye visibility. Its position, slightly below Mirfak (Alpha Persei), makesde it easy to see from early evening to dawn as long as it remained so bright. Binoculars and small telescopes showed its head or coma, which at the date shown above was now (as is typical for bright comets) larger than Jupiter (that is, about 100,000 miles in diameter), and a faint tail was visible in photographs.
 As of the date that I noticed this page was still online, the comet has long-since passed the Sun and is now heading outwards in the far reaches of the planetary system; but although the chart is well out-of-date, I decided to leave it "up" for now, as an example of resources made available online when comets are visible.