What was that? — Planning ESO follow-up for transients, variables, and Solar System objects in the era of LSST

This workshop aimed to bring together the various communities of astronomers who observe the changing night sky, from studies of nearby moving targets to the most distant transient sources. All of these fields will soon enter a new era of discovery with the beginning of the LSST, and many of the most exciting science cases will need detailed follow-up observations (for example spectroscopic characterisation), which will place significant demands on ESO’s facilities. Participants at the workshop discussed the how, why, and when of obtaining ESO observations to find out ‘what was that?’, in the era of millions of alerts per night.