Uranus and Its Moons

Uranus is relatively close these days. I took this shot of Uranus with three of its moons. You can barely make out Umbriel, which is so apparently close to Uranus that it is almost a bump on the planet.

On April 20, 2007, the comet Encke had just dipped inside the orbit of Mercury, perilously close to the sun, when a solar eruption struck and literally tore the comet's tail off. This surely has happened to comets before, but for the first time in history a spacecraft was watching. NASA's STEREO-A probe recorded a fantastic movie of the collision.

The eruption that hit Encke was a CME or "coronal mass ejection." Sky watchers on Earth are familiar with CMEs because of the auroras they create when they occasionally hit our planet. CMEs are fast-moving and massive, packing billions of tons of solar gas and magnetism into billowing clouds traveling a million-plus miles per hour.

To read more, go to http://science.nasa.gov/headlines/y2007/01oct_encke.htm

Be sure to watch the movie of the comet's tail being blown away.