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Title: An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres

Abstract

The nature of aerosols in hot exoplanet atmospheres is one of the primary vexing questions facing the exoplanet field. The complex chemistry, multiple formation pathways, and lack of easily identifiable spectral features associated with aerosols make it especially challenging to constrain their key properties. We propose a transmission spectroscopy technique to identify the primary aerosol formation mechanism for the most highly irradiated hot Jupiters (HIHJs). The technique is based on the expectation that the two key types of aerosols—photochemically generated hazes and equilibrium condensate clouds—are expected to form and persist in different regions of a highly irradiated planet’s atmosphere. Haze can only be produced on the permanent daysides of tidally locked hot Jupiters, and will be carried downwind by atmospheric dynamics to the evening terminator (seen as the trailing limb during transit). Clouds can only form in cooler regions on the nightside and morning terminator of HIHJs (seen as the leading limb during transit). Because opposite limbs are expected to be impacted by different types of aerosols, ingress and egress spectra, which primarily probe opposing sides of the planet, will reveal the dominant aerosol formation mechanism. We show that the benchmark HIHJ, WASP-121b, has a transmission spectrum consistent with partialmore » aerosol coverage and that ingress–egress spectroscopy would constrain the location and formation mechanism of those aerosols. In general, using this diagnostic we find that observations with the James Webb Space Telescope and potentially with the Hubble Space Telescope should be able to distinguish between clouds and haze for currently known HIHJs.« less

Authors:
 [1];  [2];  [3]
  1. Department of Physics, Grinnell College, 1116 8th Avenue, Grinnell, IA 50112 (United States)
  2. Department of Astronomy and Astrophysics, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637 (United States)
  3. Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States)
Publication Date:
OSTI Identifier:
22654407
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 845; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AEROSOLS; BENCHMARKS; CLOUDS; CONDENSATES; EQUILIBRIUM; IRRADIATION; JUPITER PLANET; LIMBS; PHOTOCHEMISTRY; SATELLITE ATMOSPHERES; SATELLITES; SPACE; SPECTRA; SPECTROSCOPY; TELESCOPES

Citation Formats

Kempton, Eliza M.-R., Bean, Jacob L., and Parmentier, Vivien, E-mail: kemptone@grinnell.edu. An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA84AC.
Kempton, Eliza M.-R., Bean, Jacob L., & Parmentier, Vivien, E-mail: kemptone@grinnell.edu. An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres. United States. doi:10.3847/2041-8213/AA84AC.
Kempton, Eliza M.-R., Bean, Jacob L., and Parmentier, Vivien, E-mail: kemptone@grinnell.edu. Sun . "An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres". United States. doi:10.3847/2041-8213/AA84AC.
@article{osti_22654407,
title = {An Observational Diagnostic for Distinguishing between Clouds and Haze in Hot Exoplanet Atmospheres},
author = {Kempton, Eliza M.-R. and Bean, Jacob L. and Parmentier, Vivien, E-mail: kemptone@grinnell.edu},
abstractNote = {The nature of aerosols in hot exoplanet atmospheres is one of the primary vexing questions facing the exoplanet field. The complex chemistry, multiple formation pathways, and lack of easily identifiable spectral features associated with aerosols make it especially challenging to constrain their key properties. We propose a transmission spectroscopy technique to identify the primary aerosol formation mechanism for the most highly irradiated hot Jupiters (HIHJs). The technique is based on the expectation that the two key types of aerosols—photochemically generated hazes and equilibrium condensate clouds—are expected to form and persist in different regions of a highly irradiated planet’s atmosphere. Haze can only be produced on the permanent daysides of tidally locked hot Jupiters, and will be carried downwind by atmospheric dynamics to the evening terminator (seen as the trailing limb during transit). Clouds can only form in cooler regions on the nightside and morning terminator of HIHJs (seen as the leading limb during transit). Because opposite limbs are expected to be impacted by different types of aerosols, ingress and egress spectra, which primarily probe opposing sides of the planet, will reveal the dominant aerosol formation mechanism. We show that the benchmark HIHJ, WASP-121b, has a transmission spectrum consistent with partial aerosol coverage and that ingress–egress spectroscopy would constrain the location and formation mechanism of those aerosols. In general, using this diagnostic we find that observations with the James Webb Space Telescope and potentially with the Hubble Space Telescope should be able to distinguish between clouds and haze for currently known HIHJs.},
doi = {10.3847/2041-8213/AA84AC},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 845,
place = {United States},
year = {Sun Aug 20 00:00:00 EDT 2017},
month = {Sun Aug 20 00:00:00 EDT 2017}
}