Department of Earth Sciences

The “DIVERSE” project will focus on particularly unusual exoplanets (here referred to as “Class X planets”), which have a strongly reduced interior chemistry. The result would be an atmosphere that was formed by volcanic outgassing, but one which would look quite different to that of Earth or its neighboring planets. At least for some time, the atmosphere could be dominated by volatile hydrogen. In fact, these planets would then more closely resemble ice giants, like Neptune in our solar system, where atmospheres are formed from the accretion disc during the creation of planets and are thus dominated by hydrogen and helium. However, it is still very difficult to observe helium in exoplanet atmospheres, despite some progress made in recent years. The Class X planets postulated by Noack would find themselves in the group of planets that resemble Neptune.

“If we were able to discover an exoplanet whose atmosphere primarily consisted of hydrogen without a significant presence of helium, then we would be able to call this a Class X planet,” she adds. Being able to detect a planet of this type would have major ripple effects on the wider research community. The strongly reduced chemistry in the interior would indicate that – in contrast to the rocky planets in the solar system – metal and rock would not have separated into the core and the rocky mantle above it, but would instead have remained mixed for a long time. With the aid of theoretical models, Noack and her group will lay the essential groundwork for later identifying promising candidates for Class X planets for observation. “If we manage to detect several Class X planets, then this would provide us with a statistical understanding of which planetary masses and compositions could produce a planet similar to Earth, and which could result in quite different worlds that do not exist in the Solar System.”