The discovery of planets orbiting round other stars (exoplanets) in the 1990s has led to a fundamental change in out understanding of the Universe. We now know that in our galaxy essentially every star supports a planetary system. This raise key and fundamental questions about the composition of these planets, their formation and, of course, whether any of them are capable of supporting life or do indeed support life. Answers to these questions are key for placing humankind's position in the Universe.
Exoplanets are being probed by a combination of ground based and space-borne telescopes with a number of new, bespoke missions due to start providing observational results over the next few years. Interpreting this wealth of observations requires a detailed understanding of the atomic and molecular species that make up the atmospheres of these exoplanets. Doing this requires laboratory data. The ExoMolHD project is dedicated to providing the best possible data for molecules observed or potentially observable in the atmospheres of exoplanets. These data are provided via the project website (www.exomol.com) and database. This work underpins international efforts to understand our exoplanetary neighbours.
Specific problems being addressed as part of the ExoMolHD project include:
1. Providing the very high resolution data necessary for the class of extremely large ground-based telescopes that use a special high-resolution cross-correlation technique to identify molecular species in exoplanetary atmospheres.
2. To extend the work of project 1 to allow the identification of isotopically-substituted molecules.
3. To show the effects of temperature on the rates with which molecules are broken up by the ultraviolet from their host star. Thus far photodissociation rates have assumed the molecule concerned is cold but this assumption is not valid for many of the exoplanets currently being studied.
4. To consider the effects of pressure on the way molecules in exoplanetary atmospheres absorb light.
5. To maintain and extend the ExoMol database.
