ExoMol

ExoMol

Exomol

To find out what remote planets orbiting other stars are made of, astronomers analyse the way in which their atmospheres absorb starlight of different colours and compare it to a model, or ‘spectrum’, to identify different molecules. One of such objects is Kepler-69c, which is 70 percent larger than the size of Earth. Its orbit of 242 days around a sun-like star resembles that of our neighboring planet Venus, however the composition of Kepler-69c is still unknown.

Figure 1. Artists impression of a super-Venus Kepler-69c. Image credit: NASA Ames/JPL-Caltech/T.Pyle

In collaboration with NASA AMES we have developed molecular data to model (hot) super-Venuses, yet to be detected class of object with the sulphur dominated chemistry based on Volcanic activity. According to the atmospheric chemical models, among the main constituents of the atmospheres of the rocky super-Earth or super-Venus are sulphur dioxide (SO2) and sulphur trioxide (SO3). These spectroscopically important molecules are generally not included in terrestrial exoplanet atmospheric models due to the lack of the laboratory data. We anticipate our new data will have a big impact on the future study of rocky super-Earths and super-Venuses. The recently discovered system of exoplanets TRAPIST-1 is one of the existing examples where our data will play important role in future atmospheric retrievals.

Our SO3 data set, named UYT2, is one of the biggest line lists in the ExoMol database. It contains 21 billion vibration-rotation transitions and can be used to model transit IR spectra of volcanic atmospheres for temperatures up to 800 K. In order to accomplish this data intensive task, we used some of the UK’s most advanced supercomputers, provided by the Distributed Research utilising Advanced Computing (DiRAC) project and run by the University of Cambridge. Our calculations required millions CPU hours, hundreds thousands GPU hours, and up to 5 TB of RAM, the processing power only accessible to us through the DiRAC project.