Exoplanet experts answer questions about missions to discover and probe alien worlds.
Neptune, the other blue planet, is the eighth planet in our solar system. Neptune is an ice giant.
Practically all sun-like stars have planets, and one in six has a planet the size of Earth, scientists say.
Voyager 1's rocket only had 3.5 seconds of fuel left when it sent the probe on its way 35 years ago.
This computer generated montage shows Neptune as it would appear from a spacecraft approaching Triton, Neptune's largest moon in this space wallpaper.
This week we saw debris from space shuttle Columbia found after eight years, launched a five-year mission to Jupiter and discovered potential dwarf planets.