The search for extra-terrestrial neighbours continues

10 December 2019

Astronomer Suzanne Aigrain from the Physics Department at Oxford University has been awarded almost 2 million Euros from the European Research Council to develop novel data analysis techniques that are essential to find Earth-like planets orbiting nearby stars.

Astronomers have already discovered thousands of exoplanets – planets outside our Solar System that orbit a star – but most of them are very different from the Earth, and unlikely to support life. Finding Earth-like planets that orbit nearby stars, so that we can study them in detail and look for signs of biological activity in their atmospheres, is a key goal for the exoplanet community in the coming decade.

One especially promising method to search for these nearby Earth analogs is the Radial Velocity (RV) method, which consists in measuring the tiny wobble of the host star caused by an orbiting planet. This is now a new method: back in 1995 it was used to discover the first planet around another star like the Sun, a discovery that was recently recognised by the 2019 Nobel prize in Physics. However, the precision of RV instruments has improved so much since that they should now be able to detect the tiny signal of an Earth-like planet – were it not for stellar activity. Stellar activity is caused by time-varying structures on the stellar surface (similar to Sun-spots), which perturb the RV measurements; this is the main limiting factor for RV planet searches today.

Innovative data-driven methods

‘My research group specialises in the detection and characterisation of exoplanets in the presence of stellar activity,’ explains Suzanne. ‘My background is in space-based transit surveys, which detect exoplanets by looking for the tiny dips in stellar brightness that occur when a planet passes in front of the star. In this context I have developed physically motivated but flexible, data-driven methods to disentangle planets from activity signals. More recently, I started to look at applying the same tools to RV data, where mitigating activity is even more critical. The early results were very promising, so I applied for funding to develop the idea further and put it into practice on large datasets.

‘This grant will enable me to build a dedicated group of postdocs and DPhil students to study the extensive archive of RV spectra collected over the past decade, and use it to test new and improved methods to extract the planetary signals buried in the activity "background". We will then feed the insights from that process into a major new survey, the Terra Hunting Experiment (THE), which we hope will discover habitable planets around our nearest neighbouring stars. THE will discover some of the best exoplanets characterisation targets for the next 15-20 years, and my ERC-funded team will be central to its success.

‘I am hugely proud of being awarded this grant; not only is it an endorsement of the work I have been doing for the last few years but it also reflects the transformative potential of the novel data analysis methods that I am using. On a personal note, it also means a lot to me to have secured such a competitive award not long after taking time off to have my two young children.’

Find out more about Suzanne’s work:

Image © NASA/SoHO