A continuum from clear to cloudy hot-Jupiter exoplanets without primordial water depletion

By D. Sing, Jon Fortney, N. Nikolov, H. Wakeford, T. Kataria, T. Evans, Suzanne Aigrain, Gilda E. Ballester, Adam Burrows, D. Deming and 11 more. Nature, 2015

752 citations recorded by the source corpus.

Thousands of transiting exoplanets have been discovered, but spectral analysis of their atmospheres has so far been dominated by a small number of exoplanets and data spanning relatively narrow wavelength ranges (such as 1.1–1.7 micrometres). Recent studies show that some hot-Jupiter exoplanets have much weaker water absorption features in their near-infrared spectra than predicted. The low amplitude of water signatures could be explained by very low water abundances, which may be a sign that water was depleted in the protoplanetary disk at the planet’s formation location, but it is unclear whether this level of depletion can actually occur. Alternatively, these weak signals could be the result of obscuration by clouds or hazes, as found in some optical spectra. Here we report results from a comparative study of ten hot Jupiters covering the wavelength range 0.3–5 micrometres, which allows us to resolve both the optical scattering and infrared molecular absorption spectroscopically. Our results reveal a diverse group of hot Jupiters that exhibit a continuum from clear to cloudy atmospheres. We find that the difference between the planetary radius measured at optical and infrared wavelengths is an effective metric for distinguishing different atmosphere types. The difference correlates with the spectral strength of water, so that strong water absorption lines are seen in clear-atmosphere planets and the weakest features are associated with clouds and hazes. This result strongly suggests that primordial water depletion during formation is unlikely and that clouds and hazes are the cause of weaker spectral signatures.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/f655ca79c8ddf48f78dd32f9292987b2ace39a66

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Citations in the corpus

A CONSISTENT RETRIEVAL ANALYSIS OF 10 HOT JUPITERS OBSERVED IN TRANSMISSION (2016, methodology): “We present the results of 3600 retrievals for each of the ten hot Jupiters in the Sing et al. (2016) survey.”
H2O abundances and cloud properties in ten hot giant exoplanets (2018, methodology): “The inferred oxygen abundances provide initial clues into the formation and migration scenarios of these hot Jupiters when considering the metallicities of their host stars.”
A NEW APPROACH TO ANALYZING HST SPATIAL SCANS: THE TRANSMISSION SPECTRUM OF HD 209458 b (2015, background): “…2003; Redfield et al. 2008; Snellen et al. 2008; Swain et al. 2009a,b; Linsky et al. 2010; Swain et al. 2010; Tinetti et al. 2010; Crouzet et al. 2012; Majeau et al. 2012; Waldmann et al. 2012; Todorov et al. 2013; Waldmann et al. 2013; Danielski et al. 2014; Snellen et al. 2014; Sing et al. 2016).”
HST PanCET Program: A Cloudy Atmosphere for the Promising JWST Target WASP-101b (2017, background): “— a) Temperature-Pressure profile of WASP-101b (red, this work), with WASP-31b (blue, Sing et al. (2016)).”
DETECTION OF H2O AND EVIDENCE FOR TiO/VO IN AN ULTRA-HOT EXOPLANET ATMOSPHERE (2016, methodology): “In contrast, WASP-12b is observed to have a hazy atmosphere without TiO/VO (Sing et al. 2013), despite having similar properties to WASP-121b, reinforcing the emerging picture of hot gas giant diversity (Sing et al. 2016).”
The Hubble Space Telescope PanCET Program: Exospheric Mg ii and Fe ii in the Near-ultraviolet Transmission Spectrum of WASP-121b Using Jitter Decorrelation (2019, methodology): “1D Transmission Spectra Model To help further identify absorption features, we fit a 1D analytic transmission spectral model to the data (Lecavelier des Etangs et al. 2008), following the procedures as detailed in Sing et al. (2015) and Sing (2018).”
The Complete Transmission Spectrum of WASP-39b with a Precise Water Constraint (2017, methodology): “…advanced our understanding of planetary systems, expanding theory and observations beyond our solar system (e.g. Seager & Deming 2010; Fortney et al. 2010; Marley et al. 2013; Deming et al. 2013; Stevenson et al. 2014; Sing et al. 2016; Kataria et al. 2016; Evans et al. 2016; Deming & Seager 2017).”
THE IMPRINT OF EXOPLANET FORMATION HISTORY ON OBSERVABLE PRESENT-DAY SPECTRA OF HOT JUPITERS (2016, background): “Sing et al. (2016) further show that the low water abundance in some hot Jupiters is due to the presence of clouds and hazes, and not to a water depletion during formation.”
TRANSITIONS IN THE CLOUD COMPOSITION OF HOT JUPITERS (2016, background): “Clouds play a major role in shaping the transmission spectra of hot Jupiters, impeding a precise determination of molecular abundances (Sing et al. 2016).”
Exoplanetary Atmospheres: Key Insights, Challenges, and Prospects (2019, background): “he degeneracy is through observations in the optical which, as discussed above, can constrain the scattering mechanisms and hence the presence of clouds/hazes. A recent survey of transmission spectra (244) spanning the optical and infrared range provided important constraints on both the properties ”
The Transit Light Source Effect: False Spectral Features and Incorrect Densities for M-dwarf Transiting Planets (2017, background): “…in transit spectroscopy studies to constrain the contribution of unocculted photospheric heterogeneities to exoplanet transmission spectra (Pont et al. 2008; Sing et al. 2011; Huitson et al. 2013; Jordán et al. 2013; Pont et al. 2013; Fraine et al. 2014; Sing et al. 2016; Rackham et al. 2017).”
SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5 μm (2016, background): “Thus, the slope in the transmission spectrum (∆ZJ-LM/H = 5.1±1.1) suggests the presence of hazes that are partially obscuring the signal (Sing et al. 2016).”