In the 15 years since its December 1995 launch, the SOHO spacecraft has doubled the number of comets sighted in the previous 300 years. Alex Lutkus/NASA/ESA hide caption

itoggle caption Alex Lutkus/NASA/ESA

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 hide caption

itoggle caption Lynette Cook/via NASA

Brian May wrote "We Will Rock You," "I Want It All," "Fat Bottomed Girls" and "Tie Your Mother Down," among other Queen hits. courtesy of Queen hide caption

itoggle caption courtesy of Queen

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 hide caption

itoggle caption 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. Anonymous/NASA hide caption

itoggle caption Anonymous/NASA