A planet has been discovered residing in the habitable zone of not just one, but two stars.
Located approximately 310 light-years from Earth, this distant planet exists within a binary star system and orbits its host star at a distance conducive to the presence of liquid water on its surface, as reported in a new study published in The Astronomical Journal.
This remarkable planet, designated TOI 4633 c, or "Percival," was identified with the help of citizen scientists who assisted astronomers in analyzing data from NASA's Transiting Exoplanet Survey Satellite (TESS).
TOI 4633 c was observed as it passed in front of its star, allowing TESS to detect the brief but consistent dimming of the star's light. This technique, known as the "transit method," has been instrumental in uncovering many of the thousands of exoplanets found beyond our solar system. The planet is noted to take 272 days to complete an orbit around its star, making its orbit notably long. According to the study, this is the second-longest orbital period of any TESS exoplanet and one of only five with orbits exceeding 100 days.
Because of its distance from its bright stellar host, the planet falls squarely within the habitable zone, which astronomers define as the area surrounding a star where conditions are ideal for liquid water to exist on a planet's surface—a key ingredient for life as we know it. The specific range of this zone varies based on the star's size and temperature.
For a star similar to our sun, the habitable zone is roughly located between the orbits of Venus and Mars. In contrast, for smaller, cooler stars like red dwarfs, the habitable zone is much closer. Larger, hotter stars, on the other hand, have their habitable zones positioned further out.
Further analysis revealed that the star in this remote solar system is composed of two stars orbiting around each other; however, astronomers are unable to determine which star TOI 4633 c orbits. Planets are about half as likely to form around binary stars compared to single stars, like our sun.
This discovery marks TOI 4633 c's star as the brightest known star hosting a transiting planet in the habitable zone.
"Finding planets in multi-star systems is essential for understanding how various planets can form from the same material," stated study author Nora Eisner, a research fellow at the Flatiron Institute's Center for Computational Astrophysics in New York City and the principal investigator of Planet Hunters TESS. "It's quite thrilling that we found this one."
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