On October 24, 2007, a distant comet that was as faint as magnitude +18 has suddenly brightened by almost a million- fold, becoming an easy naked eye object even from light polluted cities.
This is not the first outburst of comet 17P/Holmes; it is very similar to the one the comet experienced in 1892, which led to its discovery by Edwin Holmes. The British amateur astronomer was turning his telescope toward M31, the Great Andromeda Galaxy, when a bright fuzzball suddenly entered the field of his finderscope. Upon looking through the telescope he saw a comet about 5′ across with a stellar nucleus.
Several people expressed skepticism that Holmes had discovered such a bright comet, but it was confirmed with the naked eye by other observers on the following night. After the initial stages of the outburst, comet Holmes faded only very slowly and it remained visible to the unaided eye for about three weeks. During this interval the coma expanded dramatically, reaching about 30′ in size.
Comet Holmes lies in Perseus the Hero and is visible all night from most of the Northern Hemisphere. It is about 35° high – one-third of the way up from the horizon – at 6 P.M. local time. By 11 P.M. the comet climbs directly overhead and to the naked eye it appears as a modestly bright, small round cloud of about 3rd magnitude.
Through binoculars and small telescopes 17P/Holmes looks like a huge planetary nebula – a ghostly disk about the size of the Full Moon, surrounding a bright nucleus. The comet currently lies 156 million miles from Earth and 238 million miles from the Sun.
No one knows how long the outburst will last. Comet Holmes could remain a naked eye object for several weeks, and may even undergo a second outburst. At any rate, the comet is worth watching!
Finder map – field width 30°, stars to magnitude +6.