Gaia is ESA’s space astrometry mission and is currently surveying the skies to create the most accurate map of stars in our Galaxy.

On the day of Gaia Data Release 1 (DR1), 14 September 2016, Roeland van der Marel (STScI) and I used the Gaia DR1 proper motions of Hipparcos stars in the Large and Small Magellanic Cloud to analyse their proper motions and rotations. We submitted the resulting paper to ApJ Letters the same day. The figure below illustrates the rotation of the Large Magellanic Cloud.


This is a variation of Figure 1 from our paper. For details, see the paper on arXiv  and Gaia image of the week. This figure was produced with the help of Topcat and aplpy .

After having made extensive use of Hipparcos astrometry, it was natural for me to get involved in the Gaia astrometry mission and its scientific exploitation. I am a member of the Gaia Data Processing and Analysis Consortium (DPAC), where I am involved in the development and testing of the pipeline branch designed to characterise the orbits of exoplanetary systems. Whereas the first Gaia intermediate catalogue release is expected in mid-2016, the first astrometric orbits of exoplanet host stars are expected to be available not before 2018 (see the Date Release Scenario).

Gaia observations of naked-eye stars

As Research Fellow at ESAC in Madrid, Spain, which hosts the Gaia Science Operations centre, I acquired in-depth knowledge of the mission and had the opportunity to contribute to the mission’s bright limit extension: The Gaia survey had a nominal magnitude range of G = 6.0 – 20.0. The stars with G < 6.0, i.e. those visible to the unaided human eye, would thus not be observed by Gaia. During commissioning, we showed that a modified algorithm configuration for the Gaia on-board object detection makes it possible to efficiently observe very bright stars with G = 3.0-6.0. The 230 stars brighter than 3rd magnitude are being observed systematically as well, however using a special mode (see Martin-Fleitas, Sahlmann, et al. 2014).

Although the astrometric performance for stars with G < 6.0 has yet to be established, it is clear that this extension of the nominal magnitude range represents a significant gain for the Gaia science of nearby stars and their exoplanets.


Gaia image of a 2nd magnitude star captured in the special imaging mode. As expected, the core is heavily saturated. From Martin-Fleitas, Sahlmann, et al. 2014.