Record-breaking exoplanet found by citizen scientists

A planet in a binary star system has been found by a team of astronomers working with citizen scientists.

The Neptune-sized planet TOI 4633 c, nicknamed Percival, orbits around a pair of stars about 309 light-years away from Earth. It was first spotted by citizen scientists who were going through data collected by NASA’s Transiting Exoplanet Survey Satellite (TESS).

It was seen as it crossed in front of one of its host stars, dimming the star’s light. This “transit method” of detecting exoplanets usually finds planets with orbits close to their host star. But TOI 4633 is unusually far out compared to other planets using this method, taking 272 days to orbit around the central star.

The planet is also a record breaker. Its star is the brightest known to host a transiting planet in the “habitable” zone – where liquid water can exist on the planet’s surface.

A second planet is also believed to be orbiting the star every 34 days.

The strange system of 2 stars and possibly 2 planets is described in a paper published in the Astrophysical Journal.

“Finding planets in multi-star systems is crucial for our understanding of how you can make different planets out of the same material,” says lead author Nora Eisner, a research fellow at the Flatiron Institute’s Center for Computational Astrophysics in New York City.

“Every time I spot a possible transit, I can feel my heart beat faster and my excitement rise ,” says Simon Bentzen, a Danish citizen scientist who has volunteered with Planet Hunters TESS since 2018. “I’m very happy that I helped find the new system. I hope that the new planets can help contribute to our understanding of planet formation and help answer other interesting planetary questions.”

TESS’s Planet Hunters project has involved more than 43,000 volunteers from 90 countries to help catalogue about 25 million objects.

Eisner’s team took a closer look at TOI 4633 when 15 citizen scientists flagged a possible new planet. Follow up study confirmed the planet’s existence.

“If this planet were to have a moon, that moon would likely have a solid surface, which could then be a great place to find water,” Eisner says.

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