The study of exoplanetary systems -- planets orbiting other stars -- is one of the most rapidly evolving fields in modern astronomy. At the IoA we have several research groups which study a number of topics related to exoplanetary science, from understanding the building blocks of worlds to searching for habitable planets.
Protoplanetary Discs and Planet Formation
These dense discs which surround newborn stars represent the earliest stages of planet formation. When young stars (called protostars) coalesce out of a molecular cloud, they are shrouded in a cocoon of gas and dust. This gas and dust spins faster as it collapses under gravity, eventually forming a flat disc orbiting around the protostar. This disc of gas and dust will eventually -- after millions of years -- become a planetary system. The precise chemical makeup and behaviour of the disc will determine the types of planets that are formed.
Our research group works on the hydrodynamics of these potentially planet-bearing discs, focusing on a range of topics including the evolution of dust and gas in self-gravitating discs, and the issue of disc photoevaporation by X-rays from the young star.
Debris Discs
Debris discs are the discs of planetesimals and dust found around many nearby main sequence stars. The Solar System has its own debris disc: the asteroid and Kuiper belts, as well as the dust produced by collisions and sublimation of these objects. This dust is visible with the naked eye from the Earth as the zodiacal light; debris also collides with the Earth creating meteor showers, extinctions, and may have delivered much of our water.
As well as the implications for the habitability of extrasolar planetary systems, studying the debris disks of nearby stars provides vital clues to the outcome of planet formation processes. Many nearby discs can be seen using telescopes. By studying these images, it is possible to pinpoint the presence of unseen planets and, by studying the effect of the planets' gravity on the discs, to learn about their evolutionary history. Better understanding the debris discs around nearby stars is an essential step on the quest to find Earth-like planets.
Solar System
Of all planetary systems, our Solar System is the one we know the most about. Though the major planets are the most well-known component, the Solar System contains millions of other bodies, including asteroids, comets, moons, Kuiper belt objects, and dust. Modelling the dynamic and collisional evolution of these small bodies can teach us a lot, both about the history of the Solar system and about the behaviour of planetary systems in general.
Topics covered include the collisional evolution of irregular moons, the dynamics of the Oort cloud and Kuiper Belt, and the behaviour of dust in the inner Solar system.
Exoplanet characterisation
The first ever detection of an exoplanet orbiting a Sun-like star came in 1995. In the decades since, many thousands of exoplanets have been discovered. In recent years it has become possible to study the atmospheres of these exoplanets using a technique known as 'transmission spectroscopy' (whereby the light from the host star passes through the exoplanet's atmosphere on its way to our telescopes, carrying with it distinctive chemical fingerprints that can be analysed).
Using state-of-the-art statistical techniques, it is possible to model the formation conditions, planetary chemistry, and atmospheric makeup of these distant worlds.
Exoplanet habitability and biosignatures
One of the greatest questions in astronomy -- indeed, of all science -- is the existence of extraterrestrial life. By characterising the atmospheres of exoplanets, our research teams help to understand the range of habitable worlds.
In recent years, IoA researchers have identified a potential population of 'hycean' worlds; planets with a liquid water ocean under a hydrogen-rich atmosphere. These ocean worlds could well be habitable, and the search for biosignatures in the atmospheres of these planets is ongoing.
Polluted white dwarfs
Composition is key to our understanding of the exoplanetary conditions. The origin of life on Earth -- and potentially elsewhere -- relies on the availability of the right materials, as well as the right geological conditions.
The faint, compact remnants of stars like our Sun, known as white dwarfs, provide a unique opportunity to study the composition of exoplanetary material. The presence of metals from asteroids or comets show up in the spectra of the otherwise pure hydrogen or helium atmospheres. White dwarfs that have accreted planetary material provide unique insights into the composition, geology and loss of volatiles during planet formation.