Direct imaging discovery of a young giant planet orbiting on Solar System scales

¹ Leiden Observatory, Leiden University, Einsteinweg 55, 2333 CC Leiden, The Netherlands
² Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany
³ Department of Astrophysics/IMAPP, Radboud University, Heyen-daalseweg 135, 6525 AJ Nijmegen, The Netherlands
⁴ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
⁵ Department of Physics & Astronomy, Johns Hopkins University, 3400 N. Charles Street, Baltimore, MD 21218, USA
⁶ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
⁷ LESIA, Observatoire de Paris, PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Janssen, 92195 Meudon, France
⁸ Department of Astrophysical & Planetary Sciences, JILA, Duane Physics Bldg., 2000 Colorado Ave, University of Colorado, Boulder, CO 80309, USA
⁹ Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, Evanston, IL 60208, USA
¹⁰ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹¹ Univ. Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
¹² Academia Sinica, Institute of Astronomy and Astrophysics, 11F Astronomy-Mathematics Building, NTU/AS campus, No. 1, Section 4, Roosevelt Rd., Taipei 10617, Taiwan
¹³ Anton Pannekoek Institute for Astronomy, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
¹⁴ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
¹⁵ Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Strasse 27, 8093 Zurich, Switzerland
¹⁶ Universidade de Lisboa - Faculdade de Ciências, Campo Grande, 1749-016 Lisboa, Portugal
¹⁷ CENTRA - Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, 1049-001 Lisboa, Portugal
¹⁸ Max Planck Institute for extraterrestrial Physics, Giessenbach-straße 1, 85748 Garching, Germany
¹⁹ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice Cedex 4, France
²⁰ Aix Marseille Univ, CNRS, CNES, LAM, Marseille, France
²¹ STAR Institute, Université de Liège, Allée du Six Août 19c, 4000 Liège, Belgium
²² Institute of Physics, University of Cologne, Zülpicher Straße 77, 50937 Cologne, Germany
²³ Max Planck Institute for Radio Astronomy, Auf dem Hügel 69, 53121 Bonn, Germany
²⁴ Universidade do Porto, Faculdade de Engenharia, Rua Dr. Roberto Frias, 4200-465 Porto, Portugal
²⁵ School of Physics, University College Dublin, Belfield, Dublin 4, Ireland
²⁶ Astrophysics Group, Department of Physics & Astronomy, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK
²⁷ Departments of Physics and Astronomy, Le Conte Hall, University of California, Berkeley, CA 94720, USA
²⁸ European Southern Observatory, Casilla 19001, Santiago 19, Chile
²⁹ Advanced Concepts Team, European Space Agency, TEC-SF, ESTEC, Keplerlaan 1, NL-2201, AZ Noordwijk, The Netherlands
³⁰ University of Exeter, Physics Building, Stocker Road, Exeter EX4 4QL, UK
³¹ Fakultät für Physik, Universität Duisburg-Essen, Lotharstraße 1, 47057 Duisburg, Germany
³² Institüt für Astronomie und Astrophysik, Universität Tübingen, Auf der Morgenstelle 10, 72076 Tübingen, Germany
³³ Astronomy Department, University of Michigan, Ann Arbor, MI 48109 USA
³⁴ European Space Agency (ESA), ESA Office, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
³⁵ Department of Earth & Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA
³⁶ Max Planck Institute for Astrophysics, Karl-Schwarzschild-Str. 1, 85741 Garching, Germany
³⁷ Excellence Cluster ORIGINS, Boltzmannstraße 2, 85748 Garching bei München, Germany
³⁸ The Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871, PR China

^★ Corresponding author.

Received: 7 April 2025
Accepted: 6 June 2025

Abstract

Context. HD 135344 AB is a young visual binary system that is best known for the protoplanetary disk around the secondary star. The circumstellar environment of the A0-type primary star, on the other hand, is already depleted. HD 135344 A is therefore an ideal target for the exploration of recently formed giant planets because it is not obscured by dust.

Aims. We searched for and characterized substellar companions to HD 135344 A down to separations of about 10 au.

Methods. We observed HD 135344 A with VLT/SPHERE in the H23 and K12 bands and obtained YJ and YJH spectroscopy. In addition, we carried out VLTI/GRAVITY observations for the further astrometric and spectroscopic confirmation of a detected companion.

Results. We discovered a close-in young giant planet, HD 135344 Ab, with a mass of about 10 M_J. The multi-epoch astrometry confirms the bound nature based on common parallax and common proper motion. This firmly rules out the scenario of a non-stationary background star. The semi-major axis of the planetary orbit is approximately 15-20 au, and the photometry is consistent with that of a mid L-type object. The inferred atmospheric and bulk parameters further confirm the young and planetary nature of the companion.

Conclusions. HD 135344 Ab is one of the youngest directly imaged planets that has fully formed and orbits on Solar System scales. It is a valuable target for studying the early evolution and atmosphere of a giant planet that could have formed in the vicinity of the snowline.