Large Interferometer For Exoplanets (LIFE)

XIV. Finding terrestrial protoplanets in the galactic neighborhood

¹ Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
² NPP Fellow, NASA Goddard Space Flight Center, Greenbelt, MD, USA
³ LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
⁴ Institute for Particle Physics and Astrophysics, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zurich, Switzerland
⁵ National Center of Competence in Research PlanetS, Switzerland
⁶ Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁷ Department of Astronomy and Steward Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721, USA
⁸ Large Binocular Telescope Observatory, The University of Arizona, 933 N Cherry Ave, Tucson, AZ 85721, USA
⁹ Weltraumforschung und Planetologie, Physikalisches Institut, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
¹⁰ Université Paris-Saclay, Université Paris Cité, CEA, CNRS, AIM, 91191 Gif-sur-Yvette, France
¹¹ Department of Astrophysics, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
¹² Research School of Astronomy and Astrophysics, Australian National University, Canberra 2611, Australia
¹³ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
¹⁴ Centro de Astrobiología (CAB), CSIC-INTA, ESAC campus, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada (Madrid), Spain
¹⁵ Department of Astronomy, The University of Michigan, Ann Arbor, MI, USA
¹⁶ Freie Universität Berlin, Institute of Geological Sciences, Berlin, Germany
¹⁷ ETH Zurich, Department of Earth and Planetary Sciences, Sonneggstrasse 5, 8092 Zurich, Switzerland
¹⁸ National Center of Competence in Research “PlanetS”, Switzerland
¹⁹ Landessternwarte, Zentrum für Astronomie der Universität Heidelberg, Königstuhl 12, 69117 Heidelberg, Germany
²⁰ Dept of Physics and Astronomy, York University, 4700 Keele St, Toronto M3J 1P3, Canada
²¹ SRON Netherlands Institute for Space Research; Kapteyn Astronomical Institute, University of Groningen, Groningen, Netherlands
²² Institute of Geochemistry and Petrology, ETH Zurich, Clausiusstrasse 25, 8092 Zurich, Switzerland
²³ Center for Star and Planet Formation, Globe Institute, University of Copenhagen, Øster Voldgade 5–7, 1350 Copenhagen, Denmark
²⁴ Department of Electronics and Nanoengineering, Aalto University, Espoo, Finland
²⁵ Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246, West Bengal, India
²⁶ School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FF, UK
²⁷ Centre for Exoplanet Science, University of Edinburgh, Edinburgh EH9 3FD, UK
²⁸ UK Centre for Astrobiology, School of Physics and Astronomy, University of Edinburgh, Edinburgh, UK
²⁹ Institute of Astronomy, University of Cambridge, Cambridge, CB3 0HA, UK
³⁰ Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
³¹ Space research & Planetary Sciences (WP), Universität Bern, Gesellschaftsstrasse 6, 3012 Bern, Switzerland
³² Department of Astrophysics, University of Vienna, Türkenschanzstr. 17, 1180 Vienna, Austria
³³ Universidad de Antofagasta, Antofagasta, Chile
³⁴ Department of Physics & Astronomy, University of Exeter, Exeter, UK
³⁵ The University of Tokyo, Astrobiology Center, Tokyo, Japan
³⁶ Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden
³⁷ Globe Institute, University of Copenhagen, Denmark
³⁸ Centre for Astrophysics Research, University of Hertfordshire, Hatfield, Hertfordshire AL10 9AB, UK
³⁹ Department of Earth and Planetary Sciences, University of California, Riverside, CA 92521, USA
⁴⁰ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 118, 22100 Lund, Sweden
⁴¹ University of Belgrade, Faculty of Mathematics, Department of astronomy, Studentski trg 16, Belgrade 11000, Serbia
⁴² Astrophysics Group, Department of Physics & Astronomy, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
⁴³ Fakultät für Physik, Universität Duisburg–Essen, Lotharstraße 1, 47057 Duisburg, Germany
⁴⁴ Advanced Instrumentation and Technology Centre, Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611, Australia
⁴⁵ Nagoya University, Nagoya, Japan
⁴⁶ SRON/Leiden Observatory, Leiden, The Netherlands
⁴⁷ SRON Netherlands Institute for Space Research, Leiden, The Netherlands
⁴⁸ NOVA Optical Infrared Instrumentation Group at ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, The Netherlands
⁴⁹ University of Central Florida, USA
⁵⁰ Institut fuer Planetenforschung, DLR, and FU Berlin, Germany
⁵¹ Disruptive Space Technology Centre, RAL Space, STFC-Rutherford Appleton Laboratory, Didcot, UK
⁵² Department of Physics & Astronomy, University of Lethbridge, 4401 University Drive, Lethbridge AB, T1K 3M4, Canada
⁵³ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Bartycka 18, 00-716 Warsaw, Poland
⁵⁴ Steward Observatory and Department of Astronomy, The University of Arizona, Tucson, AZ 85721, USA
⁵⁵ INAF - Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122, Padova, Italy
⁵⁶ Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA
⁵⁷ School of Engineering and Applied Sciences, Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachussets, United States of America

^★ Corresponding authors; l.cesario@rug.nl, tim.lichtenberg@rug.nl

Received: 17 May 2024
Accepted: 9 October 2024

Abstract

Context. The increased brightness temperature of young rocky protoplanets during their magma ocean epoch makes them potentially amenable to atmospheric characterization at distances from the Solar System far greater than thermally equilibrated terrestrial exoplanets, offering observational opportunities for unique insights into the origin of secondary atmospheres and the near surface conditions of prebiotic environments.

Aims. The Large Interferometer For Exoplanets (LIFE) mission will employ a space-based midinfrared nulling interferometer to directly measure the thermal emission of terrestrial exoplanets. In this work, we seek to assess the capabilities of various instrumental design choices of the LIFE mission concept for the detection of cooling protoplanets with transient high-temperature magma ocean atmospheres at the tail end of planetary accretion. In particular, we investigate the minimum integration times necessary to detect transient magma ocean exoplanets in young stellar associations in the Solar neighborhood.

Methods. Using the LIFE mission instrument simulator (LIFEsim), we assessed how specific instrumental parameters and design choices, such as wavelength coverage, aperture diameter, and photon throughput, facilitate or disadvantage the detection of protoplan-ets. We focused on the observational sensitivities of distance to the observed planetary system, protoplanet brightness temperature (using a blackbody assumption), and orbital distance of the potential protoplanets around both G- and M-dwarf stars.

Results. Our simulations suggest that LIFE will be able to detect (S/N ≥ 7) hot protoplanets in young stellar associations up to distances of 100 pc from the Solar System for reasonable integration times (up to a few hours). Detection of an Earth-sized protoplanet orbiting a Solar-sized host star at 1 AU requires less than 30 minutes of integration time. M-dwarfs generally need shorter integration times. The contribution from wavelength regions smaller than 6 µm is important for decreasing the detection threshold and discriminating emission temperatures.

Conclusions. The LIFE mission is capable of detecting cooling terrestrial protoplanets within minutes to hours in several local young stellar associations hosting potential targets. The anticipated compositional range of magma ocean atmospheres motivates further architectural design studies to characterize the crucial transition from primary to secondary atmospheres.