Gaia and the new comets from the Oort cloud

We use Oort cloud simulations covering a time span of 5 Gyr, including the Galactic tides and stellar encounters and focussing on the last revolution of comets as they get injected into observable orbits, in order to analyze in detail the role of stars in those injections. We find this role to be very important in all parts of the cloud, so that most injected comets require the intervention of a star. Characterizing the stellar influence by the decrease of the perihelion distance, projected to the time of the next perihelion by means of tidal evolution, we identify the most efficient stars and study the properties of the corresponding encounters. We also judge the detectability of the culprit stars, responsible for the current arrival of new comets, by the Hipparcos and Gaia missions based on the magnitudes of the stars. Our main result is that the chances to detect and identify those culprits will be revolutionized by the Gaia data independent of which region of the cloud the comets come from.