Sky Watching
What Is a Comet, and What Is It Made Of?
A comet can appear from nowhere, hang in the sky for weeks with a glowing tail, and then vanish for a thousand years. These icy wanderers are leftovers from the birth of the solar system. Here is what a comet is and how it works.
What Is a Solar Eclipse, and How Does It Happen?
For a few minutes, the Moon slides in front of the Sun and turns day into an eerie twilight. A solar eclipse is a cosmic coincidence of size and distance, and one of the few celestial events you can watch with your own eyes. Here is how it works.