https://doi.org/10.1051/epjconf/201510102004
KOI-3158: The oldest known system of terrestrial-size planets
1 School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
2 Stellar Astrophysics Centre (SAC), Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C, Denmark
3 NASA Ames Research Center, Moffett Field, CA 94035, USA
4 Bay Area Environmental Research Institute, 596 1st Street West, Sonoma, CA 95476, USA
5 Department of Astronomy and Department of Planetary Science, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA
6 SETI Institute, 189 Bernardo Avenue #100, Mountain View, CA 94043, USA
7 Sydney Institute for Astronomy, School of Physics, University of Sydney, Sydney, Australia
8 Centro de Astrofísica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
9 Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
10 Department of Astronomy and McDonald Observatory, The University of Texas at Austin, USA
11 Astronomy Department, University of California, Berkeley, CA 94720, USA
12 Department of Physics and Space Sciences, Florida Institute of Technology, 150 West University Boulevard, Melbourne, FL 32901, USA
13 Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125, USA
14 Institute for Astronomy, University of Hawai‘i at Mānoa, Hilo, HI 96720-2700, USA
15 Department of Astronomy, Yale University, New Haven, CT 06520, USA
16 Space Science Institute, Boulder, CO 80301, USA
17 Department of Physics, Yale University, New Haven, CT 06511, USA
18 Max Planck Institute for Solar System Research, Göttingen, Germany
19 Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, DK-8000 Aarhus C, Denmark
20 Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255, USA
21 Departamento de Física e Astronomia, Faculdade de Ciências, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
22 Department of Planetary Sciences, University of Arizona, 1629 E University Blvd., Tucson, AZ 85721, USA
23 Department of Physics and Astronomy, Iowa State University, Ames, IA 50011, USA
24 INAF – Osservatorio Astrofisico di Torino, Via Osservatorio 20, I-10025 Pino Torinese, Italy
25 Institut furAstrophysik,Georg-August-Universität Göttingen, Friedrich-Hund-Platz1, 37077 Göttingen, Germany
a e-mail: campante@bison.ph.bham.ac.uk
Published online: 23 September 2015
The first discoveries of exoplanets around Sun-like stars have fueled efforts to find ever smaller worlds evocative of Earth and other terrestrial planets in the Solar System. While gas-giant planets appear to form preferentially around metal-rich stars, small planets (with radii less than four Earth radii) can form under a wide range of metallicities. This implies that small, including Earth-size, planets may have readily formed at earlier epochs in the Universe’s history when metals were far less abundant. We report Kepler spacecraft observations of KOI-3158, a metal-poor Sun-like star from the old population of the Galactic thick disk, which hosts five planets with sizes between Mercury and Venus. We used asteroseismology to directly measure a precise age of 11.2 ± 1.0 Gyr for the host star, indicating that KOI-3158 formed when the Universe was less than 20 % of its current age and making it the oldest known system of terrestrial-size planets. We thus show that Earth-size planets have formed throughout most of the Universe’s 13.8-billion-year history, providing scope for the existence of ancient life in the Galaxy.
© Owned by the authors, published by EDP Sciences, 2015
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
