I am Principal Investigator for an STFC-funded study of free-floating planets using data obtained from Campaign 9 of the extended K2 mission of NASA's Kepler space telescoope. We used the technique of gravitational microlensing to find evidence for planets. This is the first time that a space telescope has been used to conduct an exoplanet microlensing survey.

In work led by my postdoc, Dr Iain McDonald, we built a detection pipeline that found 27 candidate short-timescale microlensing events consistent with planetary masses. Five of these were previously unreported. Four out of these five new events are consistent with microlensing due to free-floating planets of around Earth mass (link to paper). Recently, work by a large international team led by my PhD student, David Specht, has confirmed that the fifth event is a bound exoplanet. K2-2016-BLG-0005Lb is a close analogue of Jupiter and is the first confirmed exoplanet discovered from space using gravitational lensing (link to paper).

I am Principal Investigator for the Spectroscopy and Photometry of Exoplanet Atmospheres Research Network (SPEARNET) that is pioneering an automated approach to detecting and characterising the atmospheres of exoplanets. SPEARNET has developed world-leading tools for fitting multi-wavelength exoplanet transit signals and innovative machine learning approaches for rapid fiting of planet atmosphere models to data collected from a heterogenous, globally-distributed network of optical and infrared telescopes.

I lead the ESA Euclid Exoplanet Science Working Group that is designing an exoplanet microlensing survey as an additional science activity for Euclid, which is due to be launched in July 2023. I have also been involved in exoplanet survey design studies for the NASA Nancy Grace Roman Space Telescope (Roman, previously named WFIRST), due for launch in 2027. Roman and Euclid will enable us to find cool low-mass exoplanets at larger host separations than possible with the transit method, enabling us to complete the exoplanet census started by Kepler. We are even studying the potential for them to work together.

Mapping the cool, low-mass exoplanet regime is crucial for testing planet formation theory. Unlike larger or warmer planets, cool low-mass planets are thought to remain orbiting largely at the position of their formation. Roman and Euclid will provide the first large-scale study of this regime. They will also be sensitive to planets at the outer edge of their hosts habitable zone, and to free-floating planets that may be unbound from any star.

I have pioneered a new approach to calculating the rate of microlensing in our Galaxy based on highly detailed synthetic Galactic models. This has led to the development of the Manchester-Besançon Microlensing Simulator (MaBμlS), currently the most advanced Galactic microlensing model. MaBμlS is being used by both the ESA Euclid and NASA Nancy Grace Roman Space Telescope teams to help design their exoplanet microlensing surveys.

I proposed Mutual Detectability as a game-theory based approach to the targetted search for extra-terrestrial intelligence (SETI). Mutual Detectability involves targetting systems that have an opportunity to view our planet the same way we can view theirs (e.g. via the transit method). This may lead to a mutually shared incentive to make contact as both parties realise the other party may know about their potential existence. This SETI strategy is a direct analogue of a famous problem where two strangers who've never met and cannot communicate with each other have to decide on the best way to find each other in New York city on a particular day. It's an example of a coordination game between two cooperating but non-communicating participants, described by Nobel prize-winning economist and Cold War strategist Thomas Schelling in his book The Strategy of Conflict. I show that this approach, when applied to transiting systems, leads to the idea that a good target strategy is to focus on searching for transmissions from potentially habitable transiting planets orbiting low-mass stars that are located close to the Ecliptic plane (link to the paper).