A Unified Theory for the Atmospheres of the Hot and Very Hot Jupiters: Two Classes of Irradiated Atmospheres

By Jon Fortney, K. Lodders, M. Marley, R. Freedman. 2007

673 citations recorded by the source corpus.

We highlight the importance of gaseous TiO and VO opacity on the highly irradiated close-in giant planets. The day-side atmospheres of these planets naturally fall into two classes that are somewhat analogous to the M- and L-type dwarfs. Those that are warm enough to have appreciable opacity due to TiO and VO gases we term ``pM class'' planets, and those that are cooler we term ``pL class'' planets. We calculate model atmospheres for these planets, including pressure-temperature profiles, spectra, and characteristic radiative time constants. We show that pM class planets have temperature inversions (hot stratospheres), appear ``anomalously'' bright in the mid-infrared secondary eclipse, and feature molecular bands in emission rather than absorption. From simple physical arguments, we show that they will have large day/night temperature contrasts and negligible phase shifts between orbital phase and thermal emission light curves, because radiative timescales are much shorter than possible dynamical timescales. The pL class planets absorb incident flux deeper in the atmosphere where atmospheric dynamics will more readily redistribute absorbed energy. This will lead to cooler day sides, warmer night sides, and larger phase shifts in thermal emission light curves. The boundary between these classes (~0.04-0.05 AU from a Sun-like primary for solar composition) is particularly dependent on the incident flux from the parent star, and less so on other factors. We apply these results to several planets and note that the eccentric transiting planets HD 147506b and HD 17156b alternate between the classes. Thermal emission in the optical from pM class planets is significant redward of 400 nm, making these planets attractive targets for optical detection. The difference in the observed day/night contrast between υ And b (pM class) and HD 189733b (pL class) is naturally explained in this scenario.

Subfields: Astronomy and Astrophysics, Instrumentation, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/2ba58ed7c579d7fc1adb63ac0b440160a2678b0e

How researchers see this paper

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In Astronomy and Astrophysics

1. Jon Fortney
2. N. Madhusudhan
3. A. Showman
4. D. Charbonneau
5. Sara Seager
6. J. Southworth
7. D. Deming
8. M. Marley

In Instrumentation

1. Jon Fortney
2. N. Madhusudhan
3. J. Southworth
4. A. Showman
5. H. Knutson
6. D. Charbonneau
7. D. Sing
8. Sara Seager

In Statistical and Nonlinear Physics

1. N. Madhusudhan
2. Jon Fortney
3. C. Mordasini
4. A. Showman
5. H. Knutson
6. Sara Seager
7. M. Line
8. V. Parmentier

Citations in the corpus

• TRANSMISSION SPECTRA OF THREE-DIMENSIONAL HOT JUPITER MODEL ATMOSPHERES (2009, background): “The effect is more dramatic in simulations of HD 189733b than for HD 209458b, owing mostly to a longer radiative time constant in HD 189733b (Showman et al. 2008; Fortney et al. 2008).”
• HST hot-Jupiter transmission spectral survey: evidence for aerosols and lack of TiO in the atmosphere of WASP-12b (2013, methodology): “WASP-12b has the potential to help address the stratospheric TiO hypothesis, which links the presence of TiO to thermal inversions (Fortney et al. 2008).”
• An HST optical-to-near-IR transmission spectrum of the hot Jupiter WASP-19b: detection of atmospheric water and likely absence of TiO (2013, methodology): “For both data sets, we compare to two different sets of models; one set based on the formalism of Fortney et al. (2008, 2010) and the other set based on the formalism of Burrows et al. (2010) and Howe & Burrows (2012).”
• FORMATION AND STRUCTURE OF LOW-DENSITY EXO-NEPTUNES (2011, methodology): “We take 3 γ = 0.6 √ Tirr/2000 K, which Guillot (2010) found provided a good match to detailed calculations of hot Jupiter atmospheres from Fortney et al. (2008).”
• High-precision photometry by telescope defocussing. I. The transiting planetary system WASP-5 (2009, background): “We calculate that its equilibrium temperature is Teq = 1732±80 K, which may be high enough for WASP-5b to fall into the ‘pM class’ of planets with large atmospheric opacities due to oxides of titanium and vanadium (Fortney et al. 2008).”
• DISCOVERY OF A TRANSITING PLANET AND EIGHT ECLIPSING BINARIES IN HATNet FIELD G205 (2009, background): “The theoretical radius from Fortney et al. (2008) would be 1.32RJ, 1.25RJ, and 1.17RJ, respectively, for ages of 300 Myr, 1 Gyr, and 4.5 Gyr, assuming coreless models, and 0.02 AU orbital distance.”
• The TRAPPIST survey of southern transiting planets. I. Thirty eclipses of the ultra-short period planet WASP-43 b (2012, methodology): “We have modeled the atmosphere of WASP-43 b using the methods described in Fortney et al. (2005, 2008) and Fortney & Marley (2007).”
• ATMOSPHERIC HEAT REDISTRIBUTION ON HOT JUPITERS (2013, positive): “…this timescale compar- ison could describe the pressure-, opacity-, and insolationdependence of the day-night temperature differences on hot Jupiters (Cooper & Showman 2005; Showman et al. 2008; Fortney et al. 2008; Rauscher & Menou 2010; Heng et al. 2011; Cowan & Agol 2011; Perna et al. 2012).”
• From thermal dissociation to condensation in the atmospheres of ultra hot Jupiters: WASP-121b in context (2018, methodology): “All the pressure-temperature profiles have a strong thermal inversion at the photosphere, due to the combination of absorption by TiO (Fortney et al. 2008) and the lack of water as a coolant at low pressures (Mollière et al. 2015).”
• SPITZER PHASE CURVE CONSTRAINTS FOR WASP-43b AT 3.6 AND 4.5 μm (2016, result): “We also re-derive a more precise estimate of the planet’s Bond albedo (Ab= 0.19 +0.08 −0.09) that is consistent with the expectation that hot Jupiters are generally black (Fortney et al. 2008; Burrows et al. 2008).”
• INFERENCE OF INHOMOGENEOUS CLOUDS IN AN EXOPLANET ATMOSPHERE (2013, methodology): “We use the methods of Fortney et al. (2005, 2008) to compute Kepler-7b’s one-dimensional (1D) temperature structure and emission spectrum (Fig.5).”
• C/O RATIO AS A DIMENSION FOR CHARACTERIZING EXOPLANETARY ATMOSPHERES (2012, methodology): “While the lack of a thermal inversion in WASP-14b may contradict the prediction of Fortney et al. (2008), it is also possible that condensation and gravitational settling of TiO/VO (Spiegel et al. 2009) might preclude the formation of a thermal inversion.”
• 3.6 AND 4.5 μm PHASE CURVES AND EVIDENCE FOR NON-EQUILIBRIUM CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HD 189733b (2012, background): “This differs from the predictions of 1D solar metallicity atmosphere models assuming equilibrium chemistry (e.g., Fortney et al. 2008; Burrows et al. 2008; Knutson et al. 2009a), which find that HD 189733b’s 3.6 µm band should have the lowest average opacity and, therefore, probe deepest in the…”
• CHARACTERIZING TRANSITING EXOPLANET ATMOSPHERES WITH JWST (2015, background): “Temperature inversions have been suggested to explain the emission spectra of a number of hot Jupiters (e.g., see Fortney et al. 2008; Knutson et al. 2010, and references therein), indicating the presence of visible or UV stratospheric absorbers.”
• DISEQUILIBRIUM CARBON, OXYGEN, AND NITROGEN CHEMISTRY IN THE ATMOSPHERES OF HD 189733b AND HD 209458b (2011, background): “On HD 189733b, CO2 quenches eventually (see where dotted curve diverges from dashed curve), but only at very high altitudes, and its abundance follows equilibrium at the pressure levels at which the observations are the most sensitive (∼1–10−4 bar, see Fortney et al. 2008a).”
• DETECTION OF H2O AND EVIDENCE FOR TiO/VO IN AN ULTRA-HOT EXOPLANET ATMOSPHERE (2016, background): “For instance, models predict larger temperature contrasts between the dayside and nightside hemispheres with increasing stellar irradiation and planet metallicity (Fortney et al. 2008; Dobbs-Dixon & Lin 2008; Kataria et al. 2015).”