In this talk I will place Gaia in a historical context, briefly explain how the measurements are made, then focus on a few of the scientific highlights so far: ranging from results on individual stars (the crystallisation of white dwarfs, the tidal tails of open clusters, the nearest black hole, hypervelocity stars, and Gaia’s first exoplanets) to results on our Galaxy’s largest scales, including the distance to the Galactic centre, the discovery of halo streams (relics of the tidal accretion history of the Milky Way), measurement of our Sun’s motion around the Galaxy, and the slowing down of the `bar’ at the centre of the Milky Way due dragging by our dark matter halo. As an astrometric survey mission, Gaia provides parallaxes, motions in space (proper motions and radial velocities) and astrophysical characterization (through photometry and spectroscopy) for more than one billion stars down to G 20.7 mag throughout most of the Galaxy and the Local Group galaxies. Today, it is again at the forefront of efforts to understand the structure of our Milky Way galaxy, and how it came into existence. The measurement of accurate star positions, astrometry, is the oldest branch of astronomy. He was the recipient of the Shaw Prize in Astronomy in 2022 for his lifetime’s contribution to space astrometry. He was Professor of Astronomy at Leiden University, The Netherlands (1993-2009), and amongst subsequent appointments, the Bohdan Paczynski Visiting Professor at Princeton University (2013), and adjunct professor at University College Dublin (since 2013). This juggernaut mission, still operational 10 years after launch in 2013, is in the process of creating a revolutionary celestial map of two billion stars. He was co-originator of the follow-on Gaia mission, and ESA’s project scientist from its earliest concepts in 1993 until the Critical Design Review in 2008. The spacecraft currently operates in a Lissajous orbit around the Sun– Earth L 2 Lagrangian point.With a PhD from Cambridge University, Michael Perryman’s 30-year career with the European Space Agency started with his scientific leadership of Hipparcos, 1981-1997, the pioneering satellite mission which charted the distances and motions of 100,000 stars. payload design for the next space astrometry mission Gaia (approved in 2000 as a cornerstone within the European Space Agency science program') allow to. Gaia was launched on 19 December 2013 by Arianespace using a Soyuz ST-B/ Fregat-MT rocket flying from Kourou in French Guiana. The successor to the Hipparcos mission (operational 1989–1993), Gaia is part of ESA's Horizon 2000+ long-term scientific program. This massive stellar census is providing the basic observational data to analyze a wide range of important questions related to the origin, structure and evolutionary history of the Milky Way galaxy. The spectrophotometric measurements provide detailed physical properties of all stars observed, characterizing their luminosity, effective temperature, gravity and elemental composition. The Gaia mission continues to create a precise three-dimensional map of astronomical objects throughout the Milky Way and map their motions, which encode the origin and subsequent evolution of the Milky Way. Additionally, Gaia is expected to detect thousands to tens of thousands of Jupiter-sized exoplanets beyond the Solar System by using the astrometry method, 500,000 quasars outside this galaxy and tens of thousands of known and new asteroids and comets within the Solar System. Gaia targets objects brighter than magnitude 20 in a broad photometric band that covers the extended visual range between near-UV and near infrared such objects represent approximately 1% of the Milky Way population. As its detectors are not degrading as fast as initially expected, the mission can be further extended. The spacecraft has enough micro-propulsion fuel to operate until the second quarter of 2025. To study the precise position and motion of its target objects, the spacecraft monitored each of them about 70 times over the five years of the nominal mission (2014 –2019), and continues to do so during its extension.
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