Gaia is a European Space Agency satellite. It's five year mission is to construct the largest and most precise 3D map of our galaxy, the Milky Way, this will contain over 1 billion astronomical objects, mainly stars but also planets, comets, asteroids and quasars among others.
This download is totally safe. University of Cambridge created Gaia Alerts that falls into the Educational category. Google Play shows that the tool is rated 4.4 by its users.
The latest release was on Mar 20, 2018 and this application was downloaded and set up by over 0,5K users. It's free of charge to get the installer of Gaia Alerts, also, you can have a look at users' reviews on Droid Informer. The app works fine on Android 4.1 and higher.