Gaia Data Release 2

Observational Hertzsprung-Russell diagrams^★

¹ Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
² GEPI, Observatoire de Paris, Université PSL, CNRS, 5 Place Jules Janssen, 92190 Meudon, France
³ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
⁴ Leicester Institute of Space and Earth Observation and Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
⁵ Institut de Ciències del Cosmos, Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, 08028 Barcelona, Spain
⁶ INAF – Osservatorio astronomico di Padova, Vicolo Osservatorio 5, 35122 Padova, Italy
⁷ SISSA – Scuola Internazionale Superiore di Studi Avanzati, via Bonomea 265, 34136 Trieste, Italy
⁸ Leiden Observatory, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
⁹ Science Support Office, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁰ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
¹¹ Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, 69120 Heidelberg, Germany
¹² Department of Astronomy, University of Geneva, Chemin des Maillettes 51, 1290 Versoix, Switzerland
¹³ Mission Operations Division, Operations Department, Directorate of Science, European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹⁴ Lohrmann Observatory, Technische Universität Dresden, Mommsenstraße 13, 01062 Dresden, Germany
¹⁵ European Space Astronomy Centre (ESA/ESAC), Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹⁶ Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43, 22100 Lund, Sweden
¹⁷ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
¹⁸ CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
¹⁹ Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles CP 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium
²⁰ F.R.S.-FNRS, Rue d’Egmont 5, 1000 Bruxelles, Belgium
²¹ INAF – Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Firenze, Italy
²² Telespazio Vega UK Ltd for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
²³ Laboratoire d’astrophysique de Bordeaux, Univ. Bordeaux, CNRS, B18N, allée Geoffroy Saint-Hilaire, 33615 Pessac, France
²⁴ Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking, Surrey RH5 6NT, UK
²⁵ INAF – Osservatorio Astrofisico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy
²⁶ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via Piero Gobetti 93/3, 40129 Bologna, Italy
²⁷ Serco Gestión de Negocios for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
²⁸ ALTEC SpA, Corso Marche 79, 10146 Torino, Italy
²⁹ Department of Astronomy, University of Geneva, Chemin d’Ecogia 16, 1290 Versoix, Switzerland
³⁰ Gaia DPAC Project Office, ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
³¹ SYRTE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, LNE, 61 avenue de l’Observatoire 75014 Paris, France
³² National Observatory of Athens, I. Metaxa and Vas. Pavlou, Palaia Penteli, 15236 Athens, Greece
³³ IMCCE, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Univ. Lille, 77 av. Denfert-Rochereau, 75014 Paris, France
³⁴ Royal Observatory of Belgium, Ringlaan 3, 1180 Brussels, Belgium
³⁵ Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK
³⁶ Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
³⁷ Institut d’Astrophysique et de Géophysique, Université de Liège, 19c Allée du 6 Août, B-4000 Liège, Belgium
³⁸ ATG Europe for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
³⁹ Área de Lenguajes y Sistemas Informáticos, Universidad Pablo de Olavide, Ctra. de Utrera, km 1. 41013 Sevilla, Spain
⁴⁰ ETSE Telecomunicación, Universidade de Vigo, Campus Lagoas-Marcosende, 36310 Vigo, Spain
⁴¹ Large Synoptic Survey Telescope, 950 N. Cherry Avenue, Tucson, AZ 85719, USA
⁴² Observatoire Astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l’Université, 67000 Strasbourg, France
⁴³ Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambride CB3 0HA, UK
⁴⁴ Aurora Technology for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁴⁵ Laboratoire Univers et Particules de Montpellier, Université Montpellier, Place Eugène Bataillon, CC72, 34095 Montpellier Cedex 05, France
⁴⁶ Department of Physics and Astronomy, Division of Astronomy and Space Physics, Uppsala University, Box 516, 75120 Uppsala, Sweden
⁴⁷ CENTRA, Universidade de Lisboa, FCUL, Campo Grande, Edif. C8, 1749-016 Lisboa, Portugal
⁴⁸ Università di Catania, Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Via S. Sofia 78, 95123 Catania, Italy
⁴⁹ INAF – Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
⁵⁰ Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, A1180 Vienna, Austria
⁵¹ CITIC – Department of Computer Science, University of A Coruña, Campus de Elviña s/n, 15071, A Coruña, Spain
⁵² CITIC – Astronomy and Astrophysics, University of A Coruña, Campus de Elviña s/n, 15071, A Coruña, Spain
⁵³ INAF – Osservatorio Astronomico di Roma, Via di Frascati 33, 00078 Monte Porzio Catone, Italy
⁵⁴ Space Science Data Center – ASI, Via del Politecnico SNC, 00133 Roma, Italy
⁵⁵ Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland
⁵⁶ Finnish Geospatial Research Institute FGI, Geodeetinrinne 2, 02430 Masala, Finland
⁵⁷ Isdefe for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁵⁸ Institut UTINAM UMR6213, CNRS, OSU THETA Franche-Comté Bourgogne, Université Bourgogne Franche-Comté, 25000 Besançon, France
⁵⁹ STFC, Rutherford Appleton Laboratory, Harwell, Didcot OX11 0QX, UK
⁶⁰ Departamento de Inteligencia Artificial, UNED, c/ Juan del Rosal 16, 28040 Madrid, Spain
⁶¹ Elecnor Deimos Space for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁶² Thales Services for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
⁶³ Department of Astrophysics/IMAPP, Radboud University, PO Box 9010, 6500 GL Nijmegen, The Netherlands
⁶⁴ European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany
⁶⁵ ON/MCTI-BR, Rua Gal. José Cristino 77, Rio de Janeiro, CEP 20921-400, Brazil
⁶⁶ OV/UFRJ-BR, Ladeira Pedro Antônio 43, Rio de Janeiro, CEP 20080-090, Brazil
⁶⁷ Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015-1305, USA
⁶⁸ Università di Torino, Dipartimento di Fisica, via Pietro Giuria 1, 10125 Torino, Italy
⁶⁹ Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA), ESA-ESAC, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
⁷⁰ Departamento de Estadística, Universidad de Cádiz, Calle República Árabe Saharawi s/n, 11510 Puerto Real, Spain
⁷¹ Astronomical Institute Bern University, Sidlerstrasse 5, 3012 Bern, Switzerland (present address)
⁷² EURIX S.r.l., Corso Vittorio Emanuele II 61, 10128 Torino, Italy
⁷³ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138, USA
⁷⁴ HE Space Operations BV for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁷⁵ Kapteyn Astronomical Institute, University of Groningen, Landleven 12, 9747 AD Groningen, The Netherlands
⁷⁶ Department of Computer Sciences, University of Turin, Corso Svizzera 185, 10149 Torino, Italy
⁷⁷ SRON, Netherlands Institute for Space Research, Sorbonnelaan 2, 3584CA Utrecht, The Netherlands
⁷⁸ Departamento de Matemática Aplicada y Ciencias de la Computación, Universidad de Cantabria, ETS Ingenieros de Caminos, Canales y Puertos, Avda. de los Castros s/n, 39005 Santander, Spain
⁷⁹ Unidad de Astronomía, Universidad de Antofagasta, Avenida Angamos 601, Antofagasta 1270300, Chile
⁸⁰ CRAAG – Centre de Recherche en Astronomie, Astrophysique et Géophysique, Route de l’Observatoire Bp 63 Bouzareah 16340 Alger, Algeria
⁸¹ University of Antwerp, Onderzoeksgroep Toegepaste Wiskunde, Middelheimlaan 1, 2020 Antwerp, Belgium
⁸² INAF – Osservatorio Astronomico d’Abruzzo, Via Mentore Maggini, 64100 Teramo, Italy
⁸³ INAF – Osservatorio Astronomico di Capodimonte, Via Moiariello 16, 80131 Napoli, Italy
⁸⁴ Instituto de Astronomia, Geofìsica e Ciências Atmosféricas, Universidade de São Paulo, Rua do Matão 1226, Cidade Universitaria, 05508-900 São Paulo, Brazil
⁸⁵ Department of Astrophysics, Astronomy and Mechanics, National and Kapodistrian University of Athens, Panepistimiopolis, Zografos, 15783 Athens, Greece
⁸⁶ Leibniz Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
⁸⁷ RHEA for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
⁸⁸ ATOS for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
⁸⁹ School of Physics and Astronomy, Tel Aviv University, Tel Aviv 6997801, Israel
⁹⁰ UNINOVA – CTS, Campus FCT-UNL, Monte da Caparica, 2829-516 Caparica, Portugal
⁹¹ School of Physics, O’Brien Centre for Science North, University College Dublin, Belfield, Dublin 4, Ireland
⁹² Dipartimento di Fisica e Astronomia, Università di Bologna, Via Piero Gobetti 93/2, 40129 Bologna, Italy
⁹³ Barcelona Supercomputing Center – Centro Nacional de Supercomputación, c/ Jordi Girona 29, Ed. Nexus II, 08034 Barcelona, Spain
⁹⁴ Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology, Box 848, S-981 28 Kiruna, Sweden
⁹⁵ Max Planck Institute for Extraterrestrial Physics, High Energy Group, Gießenbachstraße, 85741 Garching, Germany
⁹⁶ Astronomical Observatory Institute, Faculty of Physics, Adam Mickiewicz University, Słoneczna 36, 60-286 Poznań, Poland
⁹⁷ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Hungarian Academy of Sciences, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary
⁹⁸ Eötvös Loránd University, Egyetem tér 1-3, H-1053 Budapest, Hungary
⁹⁹ American Community Schools of Athens, 129 Aghias Paraskevis Ave. & Kazantzaki Street, Halandri, 15234 Athens, Greece
¹⁰⁰ Faculty of Mathematics and Physics, University of Ljubljana, Jadranska ulica 19, 1000 Ljubljana, Slovenia
¹⁰¹ Villanova University, Department of Astrophysics and Planetary Science, 800 E Lancaster Avenue, Villanova PA 19085, USA
¹⁰² Physics Department, University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
¹⁰³ McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213, USA
¹⁰⁴ Astronomical Institute, Academy of Sciences of the Czech Republic, Fričova 298, 25165 Ondřejov, Czech Republic
¹⁰⁵ Telespazio for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
¹⁰⁶ Institut de Physique de Rennes, Université de Rennes 1, 35042 Rennes, France
¹⁰⁷ Shanghai Astronomical Observatory, Chinese Academy of Sciences, 80 Nandan Rd, 200030 Shanghai, PR China
¹⁰⁸ School of Astronomy and Space Science, University of Chinese Academy of Sciences, Beijing 100049, PR China
¹⁰⁹ Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
¹¹⁰ DXC Technology, Retortvej 8, 2500 Valby, Denmark
¹¹¹ Las Cumbres Observatory, 6740 Cortona Drive Suite 102, Goleta, CA 93117, USA
¹¹² Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UK
¹¹³ Baja Observatory of University of Szeged, Szegedi út III/70, 6500 Baja, Hungary
¹¹⁴ Laboratoire AIM, IRFU/Service d’Astrophysique – CEA/DSM – CNRS – Université Paris Diderot, Bât. 709, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France
¹¹⁵ Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa, Poland
¹¹⁶ Faculty of Mathematics and Physics, Institute of Theoretical Physics, Charles University, Prague, Czech Republic
¹¹⁷ AKKA for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
¹¹⁸ Vitrociset Belgium for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹¹⁹ HE Space Operations BV for ESA/ESTEC, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands
¹²⁰ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, USA
¹²¹ QUASAR Science Resources for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹²² Fork Research, Rua do Cruzado Osberno, Lt. 1, 9 esq., Lisboa, Portugal
¹²³ APAVE SUDEUROPE SAS for CNES Centre Spatial de Toulouse, 18 avenue Edouard Belin, 31401 Toulouse Cedex 9, France
¹²⁴ Nordic Optical Telescope, Rambla José Ana Fernández Pérez 7, 38711 Breña Baja, Spain
¹²⁵ Spanish Virtual Observatory, Spain
¹²⁶ Fundación Galileo Galilei – INAF, Rambla José Ana Fernández Pérez 7, 38712 Breña Baja, Santa Cruz de Tenerife, Spain
¹²⁷ INSA for ESA/ESAC, Camino bajo del Castillo s/n, Urbanización Villafranca del Castillo, Villanueva de la Cañada, 28692 Madrid, Spain
¹²⁸ Departamento de Arquitectura de Computadores y Automática, Facultad de Informática, Universidad Complutense de Madrid, C/ Prof. José García Santesmases s/n, 28040 Madrid, Spain
¹²⁹ H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL, UK
¹³⁰ Institut d’Estudis Espacials de Catalunya (IEEC), Gran Capita 2-4, 08034 Barcelona, Spain
¹³¹ Applied Physics Department, Universidade de Vigo, 36310 Vigo, Spain
¹³² Stellar Astrophysics Centre, Aarhus University, Department of Physics and Astronomy, 120 Ny Munkegade, Building 1520, DK-8000 Aarhus C, Denmark
¹³³ Argelander-Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
¹³⁴ Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 Australia
¹³⁵ Sorbonne Universités, UPMC Univ. Paris 6 et CNRS, UMR 7095, Institut d’Astrophysique de Paris, 98 bis bd. Arago, 75014 Paris, France
¹³⁶ Department of Geosciences, Tel Aviv University, Tel Aviv 6997801, Israel

Received: 16 February 2018
Accepted: 16 April 2018

Abstract

Context. Gaia Data Release 2 provides high-precision astrometry and three-band photometry for about 1.3 billion sources over the full sky. The precision, accuracy, and homogeneity of both astrometry and photometry are unprecedented.

Aims. We highlight the power of the Gaia DR2 in studying many fine structures of the Hertzsprung-Russell diagram (HRD). Gaia allows us to present many different HRDs, depending in particular on stellar population selections. We do not aim here for completeness in terms of types of stars or stellar evolutionary aspects. Instead, we have chosen several illustrative examples.

Methods. We describe some of the selections that can be made in Gaia DR2 to highlight the main structures of the Gaia HRDs. We select both field and cluster (open and globular) stars, compare the observations with previous classifications and with stellar evolutionary tracks, and we present variations of the Gaia HRD with age, metallicity, and kinematics. Late stages of stellar evolution such as hot subdwarfs, post-AGB stars, planetary nebulae, and white dwarfs are also analysed, as well as low-mass brown dwarf objects.

Results. The Gaia HRDs are unprecedented in both precision and coverage of the various Milky Way stellar populations and stellar evolutionary phases. Many fine structures of the HRDs are presented. The clear split of the white dwarf sequence into hydrogen and helium white dwarfs is presented for the first time in an HRD. The relation between kinematics and the HRD is nicely illustrated. Two different populations in a classical kinematic selection of the halo are unambiguously identified in the HRD. Membership and mean parameters for a selected list of open clusters are provided. They allow drawing very detailed cluster sequences, highlighting fine structures, and providing extremely precise empirical isochrones that will lead to more insight in stellar physics. Conclusions. Gaia DR2 demonstrates the potential of combining precise astrometry and photometry for large samples for studies in stellar evolution and stellar population and opens an entire new area for HRD-based studies.