
17P/Holmes is a periodic comet in our solar system. It has been discovered by the British amateur astronomer Edwin Holmes on 6 november 1892. End of October 2007 this comet had a "outburst". It's lightstrength (magnitude) changed in a few hours from magnitude 17 (very faint) to magitude 2 (well visible to the naked eye). This is an increase of 400.000x in visibility.
The comet is still visible to the naked eve, and it looks like this in 10x50 binoculars. If you wish to see it yourself use the following picture:
