arXiv · 2003.05528
Nightside condensation of iron in an ultra-hot giant exoplanet
Abstract
Ultra-hot giant exoplanets receive thousands of times Earth's insolation. Their high-temperature atmospheres (>2,000 K) are ideal laboratories for studying extreme planetary climates and chemistry. Daysides are predicted to be cloud-free, dominated by atomic species and substantially hotter than nightsides. Atoms are expected to recombine into molecules over the nightside, resulting in different day-night chemistry. While metallic elements and a large temperature contrast have been observed, no chemical gradient has been measured across the surface of such an exoplanet. Different atmospheric chemistry between the day-to-night ("evening") and night-to-day ("morning") terminators could, however, be revealed as an asymmetric absorption signature during transit. Here, we report the detection of an asymmetric atmospheric signature in the ultra-hot exoplanet WASP-76b. We spectrally and temporally resolve this signature thanks to the combination of high-dispersion spectroscopy with a large photon-collecting area. The absorption signal, attributed to neutral iron, is blueshifted by -11+/-0.7 km s-1 on the trailing limb, which can be explained by a combination of planetary rotation and wind blowing from the hot dayside. In contrast, no signal arises from the nightside close to the morning terminator, showing that atomic iron is not absorbing starlight there. Iron must thus condense during its journey across the nightside.
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David Ehrenreich, Christophe Lovis, Romain Allart, María Rosa Zapatero Osorio, Francesco Pepe, Stefano Cristiani, Rafael Rebolo, Nuno C. Santos, Francesco Borsa, Olivier Demangeon, Xavier Dumusque, Jonay I. González Hernández, Núria Casasayas-Barris, Damien Ségransan, Sérgio Sousa, Manuel Abreu, Vardan Adibekyan, Michael Affolter, Carlos Allende Prieto, Yann Alibert, Matteo Aliverti, David Alves, Manuel Amate, Gerardo Avila, Veronica Baldini, Timothy Bandy, Willy Benz, Andrea Bianco, Émeline Bolmont, François Bouchy, Vincent Bourrier, Christopher Broeg, Alexandre Cabral, Giorgio Calderone, Enric Pallé, H. M. Cegla, Roberto Cirami, João M. P. Coelho, Paolo Conconi, Igor Coretti, Claudio Cumani, Guido Cupani, Hans Dekker, Bernard Delabre, Sebastian Deiries, Valentina D'Odorico, Paolo Di Marcantonio, Pedro Figueira, Ana Fragoso, Ludovic Genolet, Matteo Genoni, Ricardo Génova Santos, Nathan Hara, Ian Hughes, Olaf Iwert, Florian Kerber, Jens Knudstrup, Marco Landoni, Baptiste Lavie, Jean-Louis Lizon, Monika Lendl, Gaspare Lo Curto, Charles Maire, Antonio Manescau, C. J. A. P. Martins, Denis Mégevand, Andrea Mehner, Giusi Micela, Andrea Modigliani, Paolo Molaro, Manuel Monteiro, Mario Monteiro, Manuele Moschetti, Eric Müller, Nelson Nunes, Luca Oggioni, António Oliveira, Giorgio Pariani, Luca Pasquini, Ennio Poretti, José Luis Rasilla, Edoardo Redaelli, Marco Riva, Samuel Santana Tschudi, Paolo Santin, Pedro Santos, Alex Segovia Milla, Julia V. Seidel, Danuta Sosnowska, Alessandro Sozzetti, Paolo Spanò, Alejandro Suárez Mascareño, Hugo Tabernero, Fabio Tenegi, Stéphane Udry, Alessio Zanutta, Filippo Zerbi. 2020-03-11. Nightside condensation of iron in an ultra-hot giant exoplanet. https://doi.org/10.1038/s41586-020-2107-1
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