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Live from arXiv, it's our new review paper, "Aerosols in Exoplanet Atmospheres" by yours truly, @StellarPlanet, @Of_FallingStars, and @V_Parmentier, to be published in the special exoplanets edition of @jgrplanets!
https://arxiv.org/abs/2102.03480
https://arxiv.org/abs/2102.03480
As we scoured the literature of the last 10+ years, a few themes stood out. For those who study exoplanet atmospheres, these may sound familiar.
1. Aerosols are everywhere.
They show up in transmission, emission, and reflection, sculpting exoplanet transmission spectra, the emitted flux of brown dwarfs, directly imaged exoplanets, and transiting exoplanets, and exoplanet albedos
They show up in transmission, emission, and reflection, sculpting exoplanet transmission spectra, the emitted flux of brown dwarfs, directly imaged exoplanets, and transiting exoplanets, and exoplanet albedos
2. Exoplanet aerosols are spatially heterogeneous
Combined reflected light and emission observations have revealed that hot Jupiters are mostly clear on their daysides but cloudy on their western (morning) limbs and nightsides.
Combined reflected light and emission observations have revealed that hot Jupiters are mostly clear on their daysides but cloudy on their western (morning) limbs and nightsides.
While global circulation model predictions are mostly in agreement with these observations, there are still some important questions, such as how to keep the dayside clear when refractory clouds like metal oxides should blanket it
(image credit: @V_Parmentier)
(image credit: @V_Parmentier)
At the same time, brown dwarfs and wide orbit planet-mass companions show distinct variability in their light curves, an important sign of heterogeneity in their cloud coverage
(in hindsight we probably should've added a figure for this, but the review was long enough as is)
(in hindsight we probably should've added a figure for this, but the review was long enough as is)
3. Laboratory work is essential for learning more about exoplanet aerosols SO PLEASE FUND IT
How do exoplanet photochemical hazes form? What are their compositions? What do they look like? What clouds can actually condense?
We can't answer these (and more) without lab work!
How do exoplanet photochemical hazes form? What are their compositions? What do they look like? What clouds can actually condense?
We can't answer these (and more) without lab work!
Take for instance this image of exoplanet haze analogues from @horstlab: Over a range of gas compositions and temperatures, the haze material look completely different - what diversity awaits us out there?
(Original paper: https://ui.adsabs.harvard.edu/abs/2018ApJ...856L...3H/abstract)
(Original paper: https://ui.adsabs.harvard.edu/abs/2018ApJ...856L...3H/abstract)
So what lies in store in the next 10+ years? First, observations from next generation telescopes, including @NASAWebb, @NASARoman, @GMTelescope will go a long way towards constraining aerosol compositions
This includes measuring any aerosol spectral features in transmission and emission spectra and exoplanet albedos in reflected light, as well as atomic gas features at high spectral resolution in the optical and near UV to look for signs of condensation
At the same time, more sophisticated models that couple global dynamics with aerosol microphysics are needed to understand how aerosols form, evolve, and are transported in exoplanet atmospheres.
Lessons learned from these complex models can inform the development of more physical cloud models in retrieval codes, so model comparisons are vital
It also bears repeating that WE NEED TO FUND MORE LAB WORK
It also bears repeating that WE NEED TO FUND MORE LAB WORK
Finally, as we dive towards smaller planets, we'll have to worry about aerosols in their atmospheres too, and more compositionally diverse atmospheres beget more diverse aerosols as well
We'll be wise to learn from studies of aerosols in the atmospheres of the terrestrial and icy words of our own solar system, both past and present.
Hope you all enjoy the paper!
Hope you all enjoy the paper!
