A map of the large day–night temperature gradient of a super-Earth exoplanet

Demory, Brice-Olivier; Gillon, M.; Wit, Julien de; Madhusudhan, Nikku; Bolmont, Émeline; Heng, Kevin; Kataria, Tiffany; Lewis, Nikole K.; Hu, Renyu; Krick, Jessica; Stamenković, V.; Benneke, Björn; Kane, Stephen R.; Queloz, D.

doi:10.1038/nature17169

Cited by 300 publications

(360 citation statements)

References 43 publications

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“…Transits were subsequently detected by Winn et al (2011) using the MOST satellite, and Demory et al (2011) using the Spitzer Space Telescope. Winn et al (2011) find 55Cnce's mass, radius, and mean density to be 8.63±0.35 Å M , 2.00±0.14 Å R , and 5.9±1.5 g cm −3 , respectively, whereas Demory et al (2011) Gillon et al (2012), Dragomir et al (2014), and Demory et al (2016a), as well as from the ground by de Mooij et al (2014), report planet radius measurements in agreement with these studies. Altogether, their results suggest that, because 55Cnce's mean density is comparable to that of Earth, despite the greater mass (and consequently greater compression), the solid interior must be supplemented by a significant mass of water, gas, or other light elements.…”

Section: Cncesupporting

confidence: 75%

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A Search for Water in a Super-Earth Atmosphere: High-resolution Optical Spectroscopy of 55Cancri e

et al. 2017

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We present the analysis of high-resolution optical spectra of four transits of 55Cnce, a low-density super-Earth that orbits a nearby Sun-like star in under 18 hr. The inferred bulk density of the planet implies a substantial envelope, which, according to mass-radius relationships, could be either a low-mass extended or a high-mass compact atmosphere. Our observations investigate the latter scenario, with water as the dominant species. We take advantage of the Doppler cross-correlation technique, high-spectral resolution, and the large wavelength coverage of our observations to search for the signature of thousands of optical water absorption lines. Using our observations with HDS on the Subaru telescope and ESPaDOnS on the Canada-France-Hawaii Telescope, we are able to place a 3σ lower limit of 10 g mol −1 on the mean-molecular weight of 55Cnce's water-rich (volume mixing ratio >10%), optically thin atmosphere, which corresponds to an atmospheric scale-height of ∼80 km. Our study marks the first high-spectral resolution search for water in a super-Earth atmosphere, and demonstrates that it is possible to recover known water-vapor absorption signals in a nearby super-Earth atmosphere, using highresolution transit spectroscopy with current ground-based instruments.

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Section: Cncesupporting

confidence: 75%

“…However, follow-up secondary eclipse, phase-curve, and transit measurements (Demory et al , 2016a(Demory et al , 2016bRidden-Harper et al 2016;Tsiaras et al 2016), in conjunction with theoretical models (Lammer et al 2013;Ito et al 2015;Kite et al 2016), point to the existence of an envelope.…”

Section: Cncementioning

confidence: 99%

A Search for Water in a Super-Earth Atmosphere: High-resolution Optical Spectroscopy of 55Cancri e

et al. 2017

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“…Observations and subsequent analysis of have shown that rocky planets, without thick protoatmospheres, are only found up to 1.5-2 R  in size (Dressing et al 2015;Marcy et al 2014;Rogers 2015;Weiss & Marcy 2014) with some recent observations indicating that rocky planets can reach ~1.9 R  in size (Buchhave et al 2016;Demory et al 2016). If most close-orbiting planets indeed form with thick protoatmospheres then the least massive planets must have lost their captured H2 and He (see Lopez and Rice (2016) for a discussion of atmospheric formation vs. atmospheric loss).…”

Section: -10mentioning

confidence: 99%

Rocky Worlds Limited to ∼1.8 Earth Radii by Atmospheric Escape during a Star’s Extreme UV Saturation

Lehmer

Catling

2017

ApJ

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Recent observations and analysis of low mass (<10 M  ), exoplanets have found that rocky planets only have radii up to 1.5-2 R  . Two general hypotheses exist for the cause of the dichotomy between rocky and gas-enveloped planets (or possible water worlds): either low mass planets do not necessarily form thick atmospheres of a few wt. %, or the thick atmospheres on these planets easily escape driven by x-ray and extreme ultraviolet (XUV) emissions from young parent stars. Here we show that a cutoff between rocky and gas-enveloped planets due to hydrodynamic escape is most likely to occur at a mean radius of 1.760.38 (2) R  around Sunlike stars. We examine the limit in rocky planet radii predicted by hydrodynamic escape across a wide range of possible model inputs using 10,000 parameter combinations drawn randomly from plausible parameter ranges. We find a cutoff between rocky and gas-enveloped planets that agrees with the observed cutoff. The large cross-section available for XUV absorption in the extremely distended primitive atmospheres of low mass planets results in complete loss of atmospheres during the ~100 Myr phase of stellar XUV saturation. In contrast, more massive planets have less distended atmospheres and less escape, and so retain thick atmospheres through XUV saturation and then indefinitely as the XUV and escape fluxes drop over time. The agreement between our model and exoplanet data leads us to conclude that hydrodynamic escape plausibly explains the observed upper limit on rocky planet size and few planets (a "valley" or "radius gap") in the 1.5-2 R  range.

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“…Notably, the three complementary methods all yielded the same conclusions, resulting in a mass measurement for the innermost planet that is not only precise but also robust. Demory et al 2011Demory et al , 2016Winn et al 2011;Nelson et al 2014), CoRoT-7b (Léger et al 2009;Queloz et al 2009;Haywood et al 2014), WASP-47e (Becker et al 2015;Dai et al 2015;Sinukoff et al 2017b;Vanderburg et al 2017), Kepler-78b (Howard et al 2013;Pepe et al 2013;Sanchis-Ojeda et al 2013;Hatzes 2014;Grunblatt et al 2015), Kepler-10b (Batalha et al 2011;Dumusque et al 2014;Weiss et al 2016;Rajpaul et al 2017), K2-131b , HD 3167b (Vanderburg et al 2016a;Christiansen et al 2017;Gandolfi et al 2017, respectively labeled as C17 and G17 in the plot), K2-106b (Guenther et al 2017;Sinukoff et al 2017a, G17 and S17 respectively). Notably, the last two planets have two independent density measurements that are not consistent with each other, resulting in a disagreement in the interpretation of the internal composition.…”

Section: Resultsmentioning

confidence: 99%

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

et al. 2018

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Ultra-short period (USP) planets are a class of low-mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in situ formation being the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, and it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of a USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days in a grazing transit configuration. We derived the radii of the planets from the K2 light curve and used high-precision radial velocities gathered with the HARPS-N spectrograph for mass measurements. For K2-141b, we thus inferred a radius of 1.51±0.05R Å and a mass of 5.08±0.41M Å , consistent with a rocky composition and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet, although due to the grazing transits and the non-detection in the RV data set, we were not able to put a strong constraint on its density. We also report the detection of secondary eclipses and phase curve variations for K2-141b. The phase variation can be modeled either by a planet with a geometric albedo of 0.30±0.06 in the Kepler bandpass, or by thermal emission from the surface of the planet at ∼3000 K. Only follow-up observations at longer wavelengths will allow us to distinguish between these two scenarios.

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A map of the large day–night temperature gradient of a super-Earth exoplanet

Cited by 300 publications

References 43 publications

A Search for Water in a Super-Earth Atmosphere: High-resolution Optical Spectroscopy of 55Cancri e

A Search for Water in a Super-Earth Atmosphere: High-resolution Optical Spectroscopy of 55Cancri e

Rocky Worlds Limited to ∼1.8 Earth Radii by Atmospheric Escape during a Star’s Extreme UV Saturation

An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

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