The Gaia Mission
The European Space Agency's Gaia mission (see Figure 1) was launched in December 2013. Its primary mission aim is to understand the structure of our Galaxy, the Milky Way. It does this by creating the largest, most precise 3D map from a study of 'only' 1% of the Galaxy's 100 billion stars. Gaia builds on the work of a previous mission called Hipparcos. As well as having greater sensitivity and accuracy, Gaia has studied more than 30 times as many stars as Hipparcos.
While building up this map of our Galaxy, Gaia detects hundreds of objects per day that have changed in brightness or position since the last time it imaged that particular part of the sky. This leads to the Gaia Alerts program which alerts both researchers and amateur astronomers to objects of interest such as active galaxies, asteroids, variable stars and supernovae. Detecting several supernovae per week, Gaia provides a valuable stream of new potential targets.