Man vs machine: citizen science project discovers its first exoplanet

29 January 2020

Citizen science project Planet Hunters TESS proved its worth when its army of volunteers discovered an exoplanet – a planet beyond our own Solar System – that computer algorithms had missed.

The search for and discovery of planets outside our own Solar System has captured the interest of the general public since the first exoplanet detections in the mid-1990s, but with citizen science projects, members of the public don’t have to be mere spectators – they play a vital role in analysing huge swathes of data. The 20 volunteers who directly helped identify TOI-813b have all become co-authors of the detection paper.

Exoplanet TOI-813b

The exoplanet TOI-813b was discovered via the transit method – the detection of a temporary decrease in brightness of a star as a planet passes, or transits, in front of it – in data obtained by NASA’s Transiting Exoplanet Survey Satellite (TESS). TESS was launched in April 2018 and over the course of the nominal two-year mission, the satellite will record the changes in brightness of 200,000 bright nearby stars. Planet Hunters TESS looks for planetary signatures in this data with the help of tens of thousands of volunteers who have completed almost 12 million classifications since December 2018.

TOI-813b was initially missed by the algorithms due to its long orbital period. In fact, with its 83 day orbit – comparable to that of Mercury – TOI-813b is the longest period planet discovered by TESS to date. Long-period planets are harder to detect and thus less well understood than their short-period counterparts. However, these planets are vital for our overall understanding of the planet population and may even help us constrain models of how the planet in our own Solar System formed and evolved.

Predicting the future

TOI-813b is also of interest to the community as it is orbiting around an evolved (older) star, meaning that the star will soon enter a period of very rapid evolution where it will drastically increase in size. Modelling of this expansion showed that TOI-813b will be engulfed by its host star in around one billion years. Furthermore, studies of these systems can help us model the future of the Earth as the Sun starts to expand in 5.4 billion years.

Find out more about Planet Hunters TESS.

Image copyright: ©ESO/MKornmesser/Nick Risinger