The European Space Agency's Gaia spacecraft successfully launched into space today from Kourou in French Guiana. It now begins its 94 million mile journey (past the Moon!) to its orbital position. Gaia will orbit around the Sun with the Earth from a position known as "L2"; from L2, it can continuously view the sky (the Earth won't get in the way), and block out the Earth and Sun with one shield since they will both be on the same side of the spacecraft.
Gaia will measure the positions and motions of one billion stars in our galaxy. This is a huge number, but it actually comprises just 1% of the stars in the Milky Way. Astronomers will use this information to create the most precise map of our galaxy to date. Gaia will arrive at its destination in about a week, and then begin observations.
Click here to watch a video of the launch; liftoff takes place around 1:30!