[en] Over the past decade, observations of giant exoplanets (Jupiter-size) have provided key insights into their atmospheres, but the properties of lower-mass exoplanets (sub-Neptune) remain largely unconstrained because of the challenges of observing small planets. Numerous efforts to observe the spectra of super-Earths—exoplanets with masses of one to ten times that of Earth—have so far revealed only featureless spectra. Here we report a longitudinal thermal brightness map of the nearby transiting super-Earth 55 Cancri e (refs 4, 5) revealing highly asymmetric dayside thermal emission and a strong day-night temperature contrast. Dedicated space-based monitoring of the planet in the infrared revealed a modulation of the thermal flux as 55 Cancri e revolves around its star in a tidally locked configuration. These observations reveal a hot spot that is located 41 ± 12 degrees east of the substellar point (the point at which incident light from the star is perpendicular to the surface of the planet). From the orbital phase curve, we also constrain the nightside brightness temperature of the planet to 1,380 ± 400 kelvin and the temperature of the warmest hemisphere (centred on the hot spot) to be about 1,300 kelvin hotter (2,700 ± 270 kelvin) at a wavelength of 4.5 micrometres, which indicates inefficient heat redistribution from the dayside to the nightside. Our observations are consistent with either an optically thick atmosphere with heat recirculation confined to the planetary dayside, or a planet devoid of atmosphere with low-viscosity magma flows at the surface.
Gillon, Michaël ; Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
de Wit, Julien; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, USA
Madhusudhan, Nikku; Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, UK
Bolmont, Emeline; NaXys, Department of Mathematics, University of Namur, 8 Rempart de la Vierge, 5000 Namur, Belgium
Heng, Kevin; University of Bern, Center for Space and Habitability, Sidlerstrasse 5, CH-3012, Bern, Switzerland
Kataria, Tiffany; Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK
Lewis, Nikole; Space Telescope Science Institute, Baltimore, Maryland 21218, USA
Hu, Renyu; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA ; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
Krick, Jessica; Spitzer Science Center, MS 220-6, California Institute of Technology, Jet Propulsion Laboratory, Pasadena, California 91125, USA
Stamenković, Vlada; Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA ; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
Benneke, Björn; Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California 91125, USA
Kane, Stephen; Department of Physics and Astronomy, San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132, USA
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