A Year of Spectacular Comets.

Two spectacular comets graced Earth's skies during 2007. Both comets became bright enough to be seen by the unaided eye of the casual sky enthusiast . Early in 2007, Comet McNaught grew brighter than any comet in 40 years, displaying a beautiful dust tail that flowed across the sky. Comet McNaught (c/2006 P1) became known as the Great Comet of 2007 , sported unusual striations in its expansive dust tail , and showed unexpectedly complex chemistry in its ion tail . Toward the year's end, normally docile and faint Comet Holmes brightened suddenly and unexpectedly to naked eye visibility. Remarkably, Comet 17P/Holmes stayed bright for weeks even though it lies beyond the orbit of Mars . No distant comet in recent history has remained so bright for so long. In this view , a white Comet Holmes was photographed in early December posing with the Heart and Soul Nebulas .

APOD presents: Astronomy Pictures of the Year for 2007