The Helix Nebula is an example of a planetary nebula. Though it looks like a bubble or eye from Earth's point of view, the Helix is actually a trillion-mile-long tunnel of glowing gases. In its center ...
Unfortunate timing The first panel of this artist's concept depicts how Uranus's magnetosphere – its protective bubble – was behaving before the 1986 flyby of NASA's Voyager 2. The second panel shows ...