Identifying the Rotation Rate and the Presence of Dynamic Weather on Extrasolar Earth‐like Planets from Photometric Observations

Πάλλη, Ε.; Ford, Eric B.; Seager, Sara; Montañés-Rodŕıguez, P.; Vázquez, M.

doi:10.1086/528677

Cited by 123 publications

(129 citation statements)

References 27 publications

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“…The variability of the visible light curve along one complete orbit indicates variations of the surface albedo under a cloud-free sky and thus could be used to estimate the rotation periods of the planet. However, in the presence of clouds and atmospheric variability, the ability of accurately retrieving the rotation period is difficult, unless the time evolution of the cloud patterns correlates with the rotation period (Palle et al 2008). Based on our results, we expect that determining the rotation period from photometric light curves along one diurnal orbit would be more successful for planets with long rotation periods, because of small variability in the properties of clouds at a given time of the day.…”

Section: Discussionmentioning

confidence: 99%

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

2017

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We investigate the influence of the rotation period (Prot) on the mean climate of an aquaplanet, with a focus on the role of sea-ice albedo. We perform aquaplanet simulations with the atmospheric general circulation model ECHAM6 for various rotation periods from one Earth-day to 365 Earth-days in which case the planet is synchronously rotating. The global-mean surface temperature decreases with increasing Prot and sea ice expands equatorwards. The cooling of the mean climate with increasing Prot is caused partly by the high surface albedo of sea ice on the dayside and partly by the high albedo of the deep convective clouds over the substellar region. The cooling caused by these deep convective clouds is weak for non-synchronous rotations compared to synchronous rotation. Sensitivity simulations with the sea-ice model switched off show that the global-mean surface temperature is up to 27 K higher than in our main simulations with sea ice and thus highlight the large influence of sea ice on the climate. We present the first estimates of the influence of the rotation period on the transition of an Earth-like climate to global glaciation. Our results suggest that global glaciation of planets with synchronous rotation occurs at substantially lower incoming solar irradiation than for planets with slow but non-synchronous rotation

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Section: Discussionmentioning

confidence: 99%

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

2017

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“…Several aspects of characterizing habitable worlds using orbital photometry have been studied: the effect of the planet's obliquity (Gaidos & Williams 2004) and eccentricity (Cowan et al 2012), the presence of a moon (Selsis 2004;Moskovitz et al 2009), and the rotation period in the visible (Ford et al 2001;Pallé et al 2008) and infrared (Gómez-Leal et al 2012).…”

Section: Introductionmentioning

confidence: 99%

The effect of rotation and tidal heating on the thermal lightcurves of super Mercuries

Selsis¹,

Maurin²,

Hersant³

et al. 2013

A&A

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Short-period (<50 day), low-mass (<10 M ⊕ ) exoplanets are abundant, and the few of them whose radius and mass have been measured already reveal a diversity in composition. Some of these exoplanets are found on eccentric orbits and are subjected to strong tides that affect their rotation and result in significant tidal heating. Within this population, some planets are likely to be depleted in volatiles and have no atmosphere. We modeled the thermal emission of these super Mercuries to study the signatures of rotation and tidal dissipation on their infrared lightcurve. We computed the time-dependent temperature map on the surface and in the subsurface of the planet and the resulting disk-integrated emission spectrum received by a distant observer for any observation geometry. We calculated the illumination of the planetary surface for any Keplerian orbit and rotation. We included the internal tidal heat flow, vertical heat diffusion in the subsurface and generated synthetic lightcurves. We show that the different rotation periods predicted by tidal models (spin-orbit resonances, pseudo-synchronization) produce different photometric signatures, which are observable provided that the thermal inertia of the surface is high, as for solid or melted rocks (but not regolith). Tidal dissipation can also directly affect the lightcurves and make the inference of the rotation more difficult or easier depending on the existence of hot spots on the surface. Infrared lightcurve measurement with the James Webb Space Telescope and EChO can be used to infer exoplanets' rotation periods and dissipation rates and thus to test tidal models. This data will also constrain the nature of the (sub)surface by constraining the thermal inertia.

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“…However, Pallé et al (2008) demonstrated that if sufficient signal to noise can be obtained, it is possible to detect both the presence of continents and the clouds. In any case, our aim here is to characterize the photometric variability of both components combined.…”

Section: Light Curve Reconstructionsmentioning

confidence: 99%

“…Several authors have also attempted to model the diurnal photometric variability on an Earth-like planet (Ford et al 2001;Tinetti et al 2006aTinetti et al , 2006bFujii et al 2010), while other authors such as Woolf et al (2002), Arnold et al (2002), Seager et al (2005, and Montañés-Rodríguez et al (2005 have attempted to measure the characteristics of the reflected spectrum and the enhancement of Earth's reflectance at 700 nm due to vegetation. In addition, Pallé et al (2008) determined that the light scattered by the Earth as a function of time contains sufficient information, even with the presence of clouds, to accurately measure Earth's rotation period. Even crude reconstruction of the continental distribution could be attempted given sufficient signal-to-noise observations (Cowan et al 2009;Oakley & Cash 2009).…”

Section: Introductionmentioning

confidence: 99%

Reconstructing the Photometric Light Curves of Earth as a Planet Along Its History

Sanromá¹,

Πάλλη²

2011

ApJ

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By utilizing satellite-based estimations of the distribution of clouds, we have studied Earth's large-scale cloudiness behavior according to latitude and surface types (ice, water, vegetation, and desert). These empirical relationships are used here to reconstruct the possible cloud distribution of historical epochs of Earth's history such as the Late Cretaceous (90 Ma ago), the Late Triassic (230 Ma ago), the Mississippian (340 Ma ago), and the Late Cambrian (500 Ma ago), when the landmass distributions were different from today's. With this information, we have been able to simulate the globally integrated photometric variability of the planet at these epochs. We find that our simple model reproduces well the observed cloud distribution and albedo variability of the modern Earth. Moreover, the model suggests that the photometric variability of the Earth was probably much larger in past epochs. This enhanced photometric variability could improve the chances for the difficult determination of the rotational period and the identification of continental landmasses for a distant planets.

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Identifying the Rotation Rate and the Presence of Dynamic Weather on Extrasolar Earth‐like Planets from Photometric Observations

Cited by 123 publications

References 27 publications

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

The role of sea-ice albedo in the climate of slowly rotating aquaplanets

The effect of rotation and tidal heating on the thermal lightcurves of super Mercuries

Reconstructing the Photometric Light Curves of Earth as a Planet Along Its History

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