Insolation patterns on synchronous exoplanets with obliquity

Dobrovolskis, Anthony R.

doi:10.1016/j.icarus.2009.06.007

Cited by 60 publications

(34 citation statements)

References 65 publications

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“…Planets in the HZ of low mass stars are likely to find themselves in synchronous rotation due to strong tidal interactions with the host star (Dobrovolskis 2009;Barnes et al 2013). Planets in synchronous rotation will have permanent day and night hemispheres (Joshi et al 1997).…”

Section: Introductionmentioning

confidence: 99%

Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs

Kopparapu

Wolf

Arney

et al. 2017

ApJ

185

269

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Terrestrial planets in the habitable zones (HZs) of low-mass stars and cool dwarfs have received significant scrutiny recently Transit spectroscopy of such planets with JWST represents our best shot at obtaining the spectrum of a habitable planet within the next decade. As these planets are likely tidal-locked, improved 3D numerical simulations of such planetary atmospheres are needed to guide target selection. Here we use a 3-D climate system model, updated with new water-vapor absorption coefficients derived from the HITRAN 2012 database, to study ocean covered planets at the inner edge of the HZ around late-M to mid-K stars (2600K ≤ T ef f ≤ 4500K). Our results indicate that these updated water-vapor coefficients result in significant warming compared to previous studies, so the inner HZ around M-dwarfs is not as close as suggested by earlier work. Assuming synchronously rotating Earth-sized and Earth-massed planets with background 1 bar N 2 atmospheres, we find that planets at the inner -2 -HZ of stars with T ef f > 3000K undergo the classical "moist-greenhouse" (H 2 O mixing ratio > 10 −3 in the stratosphere) at significantly lower surface temperature (∼ 280K) in our 3-D model compared with 1-D climate models (∼ 340K). This implies that some planets around low mass stars can simultaneously undergo water-loss and remain habitable. However, for star with T ef f ≤ 3000K, planets at the inner HZ may directly transition to a runaway state, while bypassing the moist greenhouse water-loss entirely. We analyze transmission spectra of planets in a moist greenhouse regime, and find that there are several prominent H 2 O features, including a broad feature between 5-8 microns, within JWST MIRI instrument range. Thus, relying only upon standard Earth-analog spectra with 24-hour rotation period around M-dwarfs for habitability studies will miss the strong H 2 O features that one would expect to see on synchronously rotating planets around M-dwarf stars, with JWST.

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Section: Introductionmentioning

confidence: 99%

Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs

Kopparapu

Wolf

Arney

et al. 2017

ApJ

185

269

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“…In this work, we take into account that the atmospheres of terrestrial planets in the HZ of late-M to mid-K dwarfs cannot be assumed to be true Earth twins because they are expected to be tidally locked (Dobrovolskis 2009;Barnes et al 2013;Barnes 2017). If the planet's orbital eccentricity is near zero, this can result in synchronous rotation (Leconte et al 2015), in which one side of the planet always faces the star.…”

Section: Introductionmentioning

confidence: 99%

Dim Prospects for Transmission Spectra of Ocean Earths around M Stars

Suissa

Mandell

Wolf

et al. 2020

ApJ

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The search for water-rich Earth-sized exoplanets around low-mass stars is rapidly gaining attention because they represent the best opportunity to characterize habitable planets in the near future. Understanding the atmospheres of these planets and determining the optimal strategy for characterizing them through transmission spectroscopy with our upcoming instrumentation is essential in order to constrain their environments. For this study, we present simulated transmission spectra of tidally locked Earth-sized ocean-covered planets around late-M to mid-K stellar spectral types, utilizing GCM modeling results previously published by Kopparapu et al. (2017) as inputs for our radiative transfer calculations performed using NASA's Planetary Spectrum Generator (psg.gsfc.nasa.gov; Villanueva et al. (2018)). We identify trends in the depth of H 2 O spectral features as a function of planet surface temperature and rotation rate. These trends allow us to calculate the exposure times necessary to detect water vapor in the atmospheres of aquaplanets through transmission spectroscopy with the upcoming James Webb Space Telescope (JWST) as well as several future flagship space telescope concepts under consideration (LUVOIR and OST) for a target list constructed from the TESS Input Catalog (TIC). Our calculations reveal that transmission spectra for water-rich Earth-sized planets around low-mass stars will be dominated by clouds, with spectral features < 20 ppm, and only a small subset of TIC stars would allow for the characterization of an ocean planet in the Habitable Zone. We thus present a careful prioritization of targets that are most amenable to follow-up characterizations with next-generation instrumentation, in order to assist the community in efficiently utilizing precious telescope time.

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“…The tidal locking distance r T can be described empirically (Peale 1977;Kasting et al 1993;Dobrovolskis 2009;Edson et al 2011) according to the formula…”

Section: Synchronous Orbits Around Low-mass Starsmentioning

confidence: 99%

Geothermal heating enhances atmospheric asymmetries on synchronously rotating planets

Haqq-Misra

Kopparapu

2014

Monthly Notices of the Royal Astronomical Society

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Earth-like planets within the liquid water habitable zone of M type stars may evolve into synchronous rotators. On these planets, the sub-stellar hemisphere experiences perpetual daylight while the opposing anti-stellar hemisphere experiences perpetual darkness. Because the nightside hemisphere has no direct source of energy, the air over this side of the planet is prone to freeze out and deposit on the surface, which could result in atmospheric collapse. However, general circulation models (GCMs) have shown that atmospheric dynamics can counteract this problem and provide sufficient energy transport to the anti-stellar side.Here we use an idealized GCM to consider the impact of geothermal heating on the habitability of synchronously rotating planets. Geothermal heating may be expected due to tidal interactions with the host star, and the effects of geothermal heating provide additional habitable surface area and may help to induce melting of ice on the anti-stellar hemisphere. We also explore the persistence of atmospheric asymmetries between the northern and southern hemispheres, and we find that the direction of the meridional circulation (for rapidly rotating planets) or the direction of zonal wind (for slowly rotating planets) reverses on either side of the sub-stellar point. We show that the zonal circulation approaches a theoretical state similar to a Walker circulation only for slowly rotating planets, while rapidly rotating planets show a zonal circulation with the opposite direction. We find that a cross-polar circulation is present in all cases and provides an additional mechanism of mass and energy transport from the sub-stellar to anti-stellar point. Characterization of the atmospheres of synchronously rotating planets should include consideration of hemispheric differences in meridional circulation and examination of transport due to cross-polar flow.

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Insolation patterns on synchronous exoplanets with obliquity

Cited by 60 publications

References 65 publications

Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs

Habitable Moist Atmospheres on Terrestrial Planets near the Inner Edge of the Habitable Zone around M Dwarfs

Dim Prospects for Transmission Spectra of Ocean Earths around M Stars

Geothermal heating enhances atmospheric asymmetries on synchronously rotating planets

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