Nightside condensation of iron in an ultra-hot giant exoplanet
Creators: name: Ehrenreich, David
name: Lovis, Christophe
name: Allart, Romain
name: Osorio, María Rosa Zapatero
name: Pepe, Francesco
name: Cristiani, Stefano
name: Rebolo, Rafael
name: Santos, Nuno C.
name: Borsa, Francesco
name: Demangeon, Olivier
name: Dumusque, Xavier
name: Hernández, Jonay I. González
name: Casasayas-Barris, Núria
name: Ségransan, Damien
name: Sousa, Sérgio
name: Abreu, Manuel
name: Adibekyan, Vardan
name: Affolter, Michael
name: Prieto, Carlos Allende
name: Alibert, Yann
name: Aliverti, Matteo
name: Alves, David
name: Amate, Manuel
name: Avila, Gerardo
name: Baldini, Veronica
name: Bandy, Timothy
name: Benz, Willy
name: Bianco, Andrea
name: Bolmont, Émeline
name: Bouchy, François
name: Bourrier, Vincent
name: Broeg, Christopher
name: Cabral, Alexandre
name: Calderone, Giorgio
name: Pallé, Enric
name: Cegla, H. M.
name: Cirami, Roberto
name: Coelho, João M. P.
name: Conconi, Paolo
name: Coretti, Igor
name: Cumani, Claudio
name: Cupani, Guido
name: Dekker, Hans
name: Delabre, Bernard
name: Deiries, Sebastian
name: D'Odorico, Valentina
name: Di Marcantonio, Paolo
name: Figueira, Pedro
name: Fragoso, Ana
name: Genolet, Ludovic
name: Genoni, Matteo
name: Santos, Ricardo Génova
name: Hara, Nathan
name: Hughes, Ian
name: Iwert, Olaf
name: Kerber, Florian
name: Knudstrup, Jens
name: Landoni, Marco
name: Lavie, Baptiste
name: Lizon, Jean-Louis
name: Lendl, Monika
name: Curto, Gaspare Lo
name: Maire, Charles
name: Manescau, Antonio
name: Martins, C. J. A. P.
name: Mégevand, Denis
name: Mehner, Andrea
name: Micela, Giusi
name: Modigliani, Andrea
name: Molaro, Paolo
name: Monteiro, Manuel
name: Monteiro, Mario
name: Moschetti, Manuele
name: Müller, Eric
name: Nunes, Nelson
name: Oggioni, Luca
name: Oliveira, António
name: Pariani, Giorgio
name: Pasquini, Luca
name: Poretti, Ennio
name: Rasilla, José Luis
name: Redaelli, Edoardo
name: Riva, Marco
name: Tschudi, Samuel Santana
name: Santin, Paolo
name: Santos, Pedro
name: Milla, Alex Segovia
name: Seidel, Julia V.
name: Sosnowska, Danuta
name: Sozzetti, Alessandro
name: Spanò, Paolo
name: Mascareño, Alejandro Suárez
name: Tabernero, Hugo
name: Tenegi, Fabio
name: Udry, Stéphane
name: Zanutta, Alessio
name: Zerbi, Filippo
Publisher: name: arXiv
Year: 2020
Subjects: subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Ultra-hot giant exoplanets receive thousands of times Earth's insolation. Their high-temperature atmospheres (&gt;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.
description: Published in Nature (Accepted on 24 January 2020.) 33 pages, 11 figures, 3 tables