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We have found a spectral signature of AlO in an exoplanet's atmosphere! It's exciting because this molecule is unexpected at the pressures and temperatures we are probing. Our work is published today in A&A but can be read freely on the arxiv https://arxiv.org/abs/2004.13679
Hot Jupiter WASP43b is more massive than Jupiter but orbits much closer to it's host star. It is assumed to be tidally locked so the same side of the planet always faces towards the star. This leads to very high day-night temperature differences. [image credit:NASA/ESA/Z.Levay]
![Hot Jupiter WASP43b is more massive than Jupiter but orbits much closer to it's host star. It is assumed to be tidally locked so the same side of the planet always faces towards the star. This leads to very high day-night temperature differences. [image credit:NASA/ESA/Z.Levay]](https://pbs.twimg.com/media/Eb1ipalXkAAPlU4.jpg "Hot Jupiter WASP43b is more massive than Jupiter but orbits much closer to it's host star. It is assumed to be tidally locked so the same side of the planet always faces towards the star. This leads to very high day-night temperature differences. [image credit:NASA/ESA/Z.Levay]")
The light from the star was analysed as the planet passed infront of it (transits). Gases in the atmosphere will absorb characteristic frequencies of light, which can be used to determine which molecules we can see in the atmosphere. [image credit: NASA]
![The light from the star was analysed as the planet passed infront of it (transits). Gases in the atmosphere will absorb characteristic frequencies of light, which can be used to determine which molecules we can see in the atmosphere. [image credit: NASA]](https://pbs.twimg.com/media/Eb1kup3XQAMQ0mM.jpg "The light from the star was analysed as the planet passed infront of it (transits). Gases in the atmosphere will absorb characteristic frequencies of light, which can be used to determine which molecules we can see in the atmosphere. [image credit: NASA]")
We're looking at an altitude relatively high-up in the atmosphere, where the day and the night meet (called the terminator region).
Databases such as @ExoMol and HITEMP @hitran give detailed information about the spectra of a host of different molecules which could be found in exoplanet or stellar atmospheres.
In our study we used the data for all molecules (80+) which are currently available from these databases ( @ExoMol, HITEMP @hitran), to search for spectral signatures in the Hubble data published by @lkreidberg in 2014.
We don't know for sure why AlO would be present in the location we are probing - equilibrium chemistry suggests it would only be abundant at higher temperatures and pressures deeper in the atmosphere.
It's possible that turbulence, caused by the strong radiation from the host star, could be dredging up gases from deeper in the atmosphere.
The team led by @lkreidberg detected H2O in the atmosphere of WASP43b ( @WASPplanets) in 2014 - but the spectra for AlO wasn't published by @ExoMol until 2015! Other studies from @cfisher94, @astrojake, Weaver et al, Tsiaras et al also detected H2O signatures.
We are only looking in a small wavelength region & more data from future missions such as JWST, @ArielTelescope, @twinkle_mission will help give more confidence of the detection and abundances of the different molecules in the atmosphere of WASP43b and other exoplanets.
This work was part of an EU-funded collaboration and I was lucky to work on it together with @hetisikke, Yui Kawashima ( @SRON_Space ) + @IngoWaldmann, Christiane Helling.
