The inner four planets of the Gliese 581 system orbit the host star, a red dwarf 20 light-years from Earth, in this rendering from a National Science Foundation artist. The planet in the foreground has a 37-day orbit and, like Earth, is far enough from the star for liquid water to exist.
Lynette Cook/via NASA
The moon appears red during a lunar eclipse in the Qatari capital of Doha, 28 August 2007. It's going to happen again tonight, and be visible across North America.
Karim Jaafar/AFP/Getty Images
A picture from NASA's Hubble Space Telescope of the dwarf planet Pluto. Astronomer Michael Brown explains his role in demoting the planet in his new book, How I Killed Pluto And Why It Had It Coming.