Citizen scientists discover a unique planet in a binary star system

An artist's interpretation of TOI 4633 c, a Neptune-like exoplanet found orbiting the habitable zone of a sunlike star. The system contains a second star (right) and may also host another exoplanet (left). Credit: Ed Bell for the Simons Foundation.

In a remarkable feat, a group of astronomers and volunteer citizen scientists has uncovered a new planet located in the habitable zone of a binary star system.

This discovery, made using data from NASA’s Transiting Exoplanet Survey Satellite (TESS), highlights a Neptune-like planet that completes an orbit around its star every 272 days.

This finding is particularly special because the planet orbits a very bright star, the brightest known to have a transiting planet in its habitable zone.

The planet, formally named TOI 4633 c but affectionately nicknamed Percival, was first spotted by volunteers through the Planet Hunters TESS program.

This initiative allows anyone with internet access to help identify potential planets in the data collected by TESS. Simon Bentzen, a dedicated Danish volunteer since 2018, expressed his thrill at contributing to such a significant discovery.

The system’s complexity extends beyond this new planet. Preliminary observations suggest the presence of a second, yet-to-be-confirmed planet with a much shorter 34-day orbit.

Additionally, what was initially thought to be a single star turned out to be two stars orbiting each other.

This binary nature of the star system was confirmed through archival data spanning 119 years, although currently, the stars appear so close together from Earth that they cannot be individually distinguished.

This dual-star system offers a valuable case study for scientists exploring planet formation and stability in binary systems.

Nora Eisner, the study’s lead author from the Flatiron Institute’s Center for Computational Astrophysics, emphasized the rarity of planets forming in such systems and the importance of this discovery in understanding the diversity of planetary systems.

The research findings were published in The Astrophysical Journal, detailing how the team utilized the “transit method” to detect the planet.

This method involves observing the dimming of a star’s light as a planet passes in front of it, similar to a solar eclipse. The planet’s significant distance from its star in such a tight orbit adds to the uniqueness of this discovery.

Although TOI 4633 c is in the habitable zone, where conditions might allow for liquid water, it doesn’t have a solid surface and is likely enveloped in a thick atmosphere of water vapor, hydrogen, and methane.

However, if this planet has moons, they could potentially have solid surfaces that might support water and, possibly, life.

The insights gained from this system could also improve predictions for finding new exoplanets in binary star systems, which nearly half of all sun-like stars are part of. Further studies are planned, but it will be at least 30 years before the two stars are distant enough to analyze more precisely.

This discovery not only advances our understanding of planetary systems but also underscores the critical role of citizen science in astronomical research. Eisner encourages anyone interested in assisting with further discoveries to join the Planet Hunters TESS project.

Source: Simons Foundation.