From Hipparcos to Gaia

Abstract

Abstract. The measurement of the positions, distances, motions and luminosities of stars represents the foundations of modern astronomical knowledge. Launched at the end of the eighties, the ESA Hipparcos satellite was the first space mission dedicated to such measurements. Hipparcos improved position accuracies by a factor of 100 compared to typical ground-based results and provided astrometric and photometric multi-epoch observations of 118,000 stars over the entire sky. The impact of Hipparcos on astrophysics has been extremely valuable and diverse. Building on this important European success, the ESA Gaia cornerstone mission promises an even more impressive advance. Compared to Hipparcos, it will bring a gain of a factor 50 to 100 in position accuracy and of a factor of 10,000 in star number, collecting photometric, spectrophotometric and spectroscopic data for one billion celestial objects. During its 5-year flight, Gaia will measure objects repeatedly, up to a few hundred times, providing an unprecedented database to study the variability of all types of celestial objects. Gaia will bring outstanding contributions, directly or indirectly, to most fields of research in astrophysics, such as the study of our Galaxy and of its stellar constituents, and the search for planets outside the solar system.

TheGaiamission

“…The Gaia Data Processing and Analysis Consortium (DPAC) is responsible for the processing and calibration of the Gaia data. The first intermediate release of Gaia data (Gaia Collaboration 2016) comprises astrometry (Lindegren et al 2016), photometry (van Leeuwen et al 2016, and variability (Eyer et al 2016); later releases will include BP/RP and RVS data. The validation of the data is described in Arenou et al (2016) and the Gaia Archive is described in Salgado et al (2016).…”

“…The wavelength coverage of the astrometric instrument, defining the unfiltered, white-light photometric G band (for Gaia), is 330-1050 nm (Carrasco et al 2016;van Leeuwen et al 2016). These photometric data have a high signal-to-noise ratio and are particularly suitable for variability studies (Eyer et al 2016). Unlike its predecessor mission Hipparcos, which selected its targets for observation based on a predefined input catalogue loaded on board (Turon et al 1993), Gaia performs an unbiased, flux-limited survey of the sky.…”

“…An overview of the variable star processing can be found in Eyer et al (2014). The treatment of variable stars for Gaia DR1 is described in Eyer et al (2016) and Clementini et al (2016). Astrophysical parameter inference.…”

Transient astronomy with the Gaia satellite

“…Upon reaching L2 (second Lagrange point), its 5 year mission is to measure astrometry, photometry and spectroscopy for one billion targets with magnitudes in the range V ∼ 6-20. Each target star will be measured on average 80 times, leading to precise measurements of parallax, proper motions and photometric variability [1]. Gaia will enable the study and classification of huge numbers of variable sources, including eclipsing binaries, RR Lyrae, Cepheids, longperiod variables, pulsating stars, cataclysmic variables (CVs) and active galactic nuclei (AGNs).…”

Where Is the Flux Going? The Long-term Photometric Variability of Boyajian’s Star

“…A powerful new resource for detecting photometric variability across the entire sky is Gaia (e.g., Eyer et al 2017;Belokurov et al 2017;Deason et al 2017). While variability information is not included in the first Gaia data release (Gaia Collaboration et al 2016a), Belokurov et al (2017) showed that it is possible to identify variable stars by comparing the reported flux uncertainties in the Gaia DR1 catalog to the expected photon noise.…”