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.