Gaia 1 and 2. A pair of new Galactic star clusters

S. E. Koposov, V. Belokurov, G. Torrealba

Research output: Contribution to journalArticlepeer-review


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 ultrafaint 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 (2.2 × 104 M⊙), large (∼9 pc) and nearby (4.6 kpc) cluster, situated 10 arcmin 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.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Early online date15 May 2017
Publication statusPublished - 1 Sep 2017


  • astro-ph.GA

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