Letter to the Editor

A stellar occultation by the transneptunian object (50000) Quaoar observed by CHEOPS^⋆⋆,⋆

¹ Universidade Federal do Rio de Janeiro – Observatório do Valongo, Ladeira Pedro Antônio 43, CEP 20.080-090 Rio de Janeiro, Brazil
e-mail: bmorgado@ov.ufrj.br
² Observatório Nacional/MCTI, R. General José Cristino 77, CEP 20921-400 Rio de Janeiro, Brazil
³ Laboratório Interinstitucional de e-Astronomia – LIneA, Rua Gal. José Cristino 77, Rio de Janeiro 20921-400, Brazil
⁴ INAF, Osservatorio Astrofisico di Catania, Via S. Sofia 78, 95123 Catania, Italy
⁵ Institute of Physics, Federal University of Uberlândia, Uberlândia-MG, Brazil
⁶ UNESP – São Paulo State University, Grupo de Dinâmica Orbital e Planetologia, CEP 12516-410 Guaratinguetá, SP, Brazil
⁷ LESIA, Observatoire de Paris, Université PSL, Sorbonne Université, Université de Paris, CNRS, 92190 Meudon, France
⁸ Physikalisches Institut, University of Bern, Sidlerstrasse 5, 3012 Bern, Switzerland
⁹ Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
¹⁰ Institut Polytechnique des Sciences Avancées IPSA, 63 Boulevard de Brandebourg, 94200 Ivry-sur-Seine, France
¹¹ Institut de Mécanique Céleste et de Calcul des Éphémérides, IMCCE, Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ Paris 06, Univ. Lille, 77, Av. Denfert-Rochereau, 75014 Paris, France
¹² Astrophysics Group, Keele University, Staffordshire ST5 5BG, UK
¹³ Federal University of Technology – Paraná (UTFPR/DAFIS), Rua Sete de Setembro, 3165, CEP 80230-901 Curitiba, PR, Brazil
¹⁴ ETH Zurich, Department of Physics, Wolfgang-Pauli-Strasse 2, 8093 Zurich, Switzerland
¹⁵ Cavendish Laboratory, JJ Thomson Avenue, Cambridge CB3 0HE, UK
¹⁶ Instituto de Astrofisica e Ciencias do Espaco, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁷ Instituto de Astrofísica de Andalucía, IAA-CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
¹⁸ Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden
¹⁹ Centre for Exoplanet Science, SUPA School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK
²⁰ Observatoire Astronomique de l’Université de Genève, Chemin Pegasi 51, Versoix, Switzerland
²¹ Observatoire de la Côte d’Azur, Laboratoire Lagrange UMR7293 CNRS, Nice, France
²² NaXys, University of Namur, 8 Rempart de la Vierge, Namur 5000, Belgium
²³ Science and Operations Department – Science Division (SCI-SC), Directorate of Science, European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 Noordwijk, The Netherlands
²⁴ Reedy Creek Observatory, Gold Coast, Queensland, Australia
²⁵ Trans-Tasman Occultation Alliance (TTOA), PO Box 3181, Wellington, New Zealand
²⁶ Instituto de Astrofisica de Canarias, 38200 La Laguna, Tenerife, Spain
²⁷ Departamento de Astrofisica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
²⁸ Institut de Ciencies de l’Espai (ICE, CSIC), Campus UAB, Can Magrans s/n, 08193 Bellaterra, Spain
²⁹ Institut d’Estudis Espacials de Catalunya (IEEC), 08034 Barcelona, Spain
³⁰ Admatis, 5. Kandó Kálmán Street, 3534 Miskolc, Hungary
³¹ Depto. de Astrofisica, Centro de Astrobiologia (CSIC-INTA), ESAC Campus, 28692 Villanueva de la Cañada, Madrid, Spain
³² Departamento de Fisica e Astronomia, Faculdade de Ciencias, Universidade do Porto, Rua do Campo Alegre, 4169-007 Porto, Portugal
³³ Space Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, Austria
³⁴ Université Grenoble Alpes, CNRS, IPAG, 38000 Grenoble, France
³⁵ Institute of Planetary Research, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany
³⁶ Université de Paris, Institut de physique du globe de Paris, CNRS, 75005 Paris, France
³⁷ Centre for Mathematical Sciences, Lund University, Box 118 221 00 Lund, Sweden
³⁸ Aix Marseille Univ, CNRS, CNES, LAM, 38 Rue Frédéric Joliot-Curie, 13388 Marseille, France
³⁹ Astrobiology Research Unit, Université de Liège, Allée du 6 Août 19C, 4000 Liège, Belgium
⁴⁰ Space sciences, Technologies and Astrophysics Research (STAR) Institute, Université de Liège, Allée du 6 Août 19C, 4000 Liège, Belgium
⁴¹ Leiden Observatory, University of Leiden, PO Box 9513, 2300 RA Leiden, The Netherlands
⁴² Department of Space, Earth and Environment, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden
⁴³ Dipartimento di Fisica, Universita degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino, Italy
⁴⁴ University of Vienna, Department of Astrophysics, Türkenschanzstrasse 17, 1180 Vienna, Austria
⁴⁵ Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL, UK
⁴⁶ Konkoly Observatory, Research Centre for Astronomy and Earth Sciences, Konkoly Thege Miklós út 15-17, 1121 Budapest, Hungary
⁴⁷ ELTE Eötvös Loránd University, Institute of Physics, Pázmány Péter sétány 1/A, 1117 Budapest, Hungary
⁴⁸ IMCCE, UMR8028 CNRS, Observatoire de Paris, PSL Univ., Sorbonne Univ., 77 av. Denfert-Rochereau, 75014 Paris, France
⁴⁹ Institut d’astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, 98bis blvd. Arago, 75014 Paris, France
⁵⁰ INAF, Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
⁵¹ Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, 1180 Vienna, Austria
⁵² Institute of Optical Sensor Systems, German Aerospace Center (DLR), Rutherfordstrasse 2, 12489 Berlin, Germany
⁵³ Dipartimento di Fisica e Astronomia “Galileo Galilei”, Universita degli Studi di Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
⁵⁴ ESTEC, European Space Agency, 2201 AZ Noordwijk, NL, The Netherlands
⁵⁵ Zentrum für Astronomie und Astrophysik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
⁵⁶ Institut für Geologische Wissenschaften, Freie Universität Berlin, 12249 Berlin, Germany
⁵⁷ ELTE Eötvös Loránd University, Gothard Astrophysical Observatory, Szent Imre h. u. 112, 9700 Szombathely, Hungary
⁵⁸ MTA-ELTE Exoplanet Research Group, Szent Imre h. u. 112, 9700 Szombathely, Hungary
⁵⁹ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

Received: 8 June 2022
Accepted: 9 August 2022

Abstract

Context. Stellar occultation is a powerful technique that allows the determination of some physical parameters of the occulting object. The result depends on the photometric accuracy, the temporal resolution, and the number of chords obtained. Space telescopes can achieve high photometric accuracy as they are not affected by atmospheric scintillation.

Aims. Using ESA’s CHEOPS space telescope, we observed a stellar occultation by the transneptunian object (50000) Quaoar. We compare the obtained chord with previous occultations by this object and determine its astrometry with sub-milliarcsecond precision. Also, we determine upper limits to the presence of a global methane atmosphere on the occulting body.

Methods. We predicted and observed a stellar occultation by Quaoar using the CHEOPS space telescope. We measured the occultation light curve from this dataset and determined the dis- and reappearance of the star behind the occulting body. Furthermore, a ground-based telescope in Australia was used to constrain Quaoar’s limb. Combined with results from previous works, these measurements allowed us to obtain a precise position of Quaoar at the occultation time.

Results. We present the results obtained from the first stellar occultation by a transneptunian object using a space telescope orbiting Earth; it was the occultation by Quaoar observed on 2020 June 11. We used the CHEOPS light curve to obtain a surface pressure upper limit of 85 nbar for the detection of a global methane atmosphere. Also, combining this observation with a ground-based observation, we fitted Quaoar’s limb to determine its astrometric position with an uncertainty below 1.0 mas.

Conclusions. This observation is the first of its kind, and it shall be considered as a proof of concept of stellar occultation observations of transneptunian objects with space telescopes orbiting Earth. Moreover, it shows significant prospects for the James Webb Space Telescope.