Sun 1, Comet Tail 0

Here's a movie for the "way cool" files. The STEREO spacecraft was busy studying the Sun when it spotted Comet 2P/Encke. The icy snowball orbits the Sun every three years, so astronomers know Encke pretty well. Still, it's always nice to be surprised.

Click on the image at right to load the 6 MB movie. You'll see Encke coming into the frame from the left and drifting toward the bottom right of the screen. About halfway through the video, the Sun erupts and releases a massive coronal mass ejection. The CME plows into Encke and blows away the comet's plasma tail. This is the first time astronomers have witnessed a "detachment event." Comets have been known to lose their plasma tails, but until now nobody had ever watched as it happened.

Now if CMEs can do that to a comet, imagine what massive ones do to Earth's atmosphere. No wonder we see auroras as far south as Texas during a major solar storm.

The results of this research, led by Angelos Vourlidas (Naval Research Laboratory), will appear in the October 10th Astrophysical Journal Letters.