Bright Interlopers

Comet McNaught glows above the mountains of Chile in this 2007 image. Experts predict that two comets could put in brilliant displays in 2013. Comets are balls of ice and rock from the outer reaches of the solar system. As they approach the Sun, some of their ice vaporizes, surrounding the comet itself with a cloud of gas and dust. Radiation and particles from the Sun push some of this material away from the comet, creating a tail that can span hundreds of thousands of miles. [ESO/H.H. Hyer]