* Astronomy

Title: Gaia 1 and 2. A pair of new satellites of the Galaxy
Author: S. E. Koposov (1), V. Belokurov (1), G. Torrealba (1) ((1) Institute of Astronomy, University of Cambridge)

We present the results of the very first search for faint Milky Way satellites in the Gaia data. Using stellar positions only, we are able to re-discover objects detected in much deeper data as recently as the last couple of years. While we do not identify new prominent ultra-faint dwarf galaxies, we report the discovery of two new star clusters, Gaia 1 and Gaia 2. Gaia 1 is particularly curious, as it is a massive (1.4 x 10^4 solar masses), large (~ 9 pc) and nearby (4.6 kpc) cluster, situated 10' away from the brightest star on the sky, Sirius! Even though this satellite is detected at significance in excess of 10, it was missed by previous sky surveys. We conclude that Gaia possesses powerful and unique capabilities for satellite detection thanks to its unrivalled angular resolution and highly efficient object classification.

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