 |
 |
||
 |
|
||
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
||||||||
 |
Space Topics: Asteroids and CometsThe Year in Pictures: 2007In with a Comet, Out with a Comet: 17/P Holmes
On October 24, 2007, a previously quiescent comet burst into activity, brightening by a factor of nearly a million overnight. Over the ensuing weeks Comet 17/P Holmes continued to brighten, and was easily visible to the naked eye, appearing clearly non-stellar from dark sky sites. As its coma continued to spread, though, it dimmed, becoming more difficult to see with the naked eye. By early November the dimming coma had spread so wide that it was physically larger than the Sun, giving the comet the largest (though not anywhere close to the most massive) atmosphere in the solar system. This view of Comet 17P/Holmes was captured by amateur astronomer Iván Éder from Mount Pilis, Budapest, Hungary, on November 7. Unlike comet McNaught, whose tail fanned out across the sky at the beginning of 2007, comet Holmes' blue ion tail appears as a pudgy fan. The difference arises from different viewing geometry. A comet's tail spreads in the direction away from the Sun. Earth's viewpoint on McNaught was from the side; our view on Holmes is almost directly down its tail, greatly foreshortening it. The green and blue colors in the tail are caused by molecules fluorescing in solar radiation. |
|||||||||
 |
 |
|||||||||
[ what is this? ]