A team of astronomers from the University of Birmingham has made an exciting discovery in the BEBOP-1 or TOI-1338 system—a rare multiplanetary circumbinary system. Using the Doppler method, they have found a second planet, which they have named BEBOP-1c. This finding provides valuable insights into the formation of planets around binary star systems.
Circumbinary systems are unique because planets orbit around two stars at their center, unlike our Solar System where planets orbit around a single star. The researchers’ findings have been published in the latest issue of the journal Nature Astronomy.
The newly discovered planet, BEBOP-1c, is named after the project that collected the data—Binaries Escorted By Orbiting Planets (BEBOP). It is also referred to as TOI-1338. In 2020, another planet in the same system, TOI-1338b, was discovered using data from NASA’s TESS space telescope, to which the University of Birmingham team also contributed. TOI-1338b was detected using the transit method, as it passed in front of the brighter of the two stars on multiple occasions.
Lead author Dr. Matthew Standing, who completed his PhD at the University of Birmingham and is now a researcher at The Open University, explained that while the transit method allowed them to measure the size of TOI-1338b, they couldn’t determine its mass, which is a crucial parameter. Therefore, the team employed the Doppler method, also known as the wobble or radial-velocity method, to accurately measure the velocity of the stars.
Dr. Matthew’s former supervisor, Professor Amaury Triaud from the University of Birmingham, noted that this method, which led to the first exoplanet detection, earned the Nobel Prize in 2019 for Mayor and Queloz.
The discovery of BEBOP-1c, with an orbital period of 215 days and a mass 65 times larger than Earth, provides significant insights into circumbinary systems. Only a total of 12 such systems have been identified to date, and this is only the second system known to host more than one planet. The observations faced challenges, including the interruption caused by the COVID-19 pandemic, when telescopes in Chile were closed for six months during a crucial part of the planet’s orbit.
Despite these challenges, the team persisted and confirmed the existence of BEBOP-1c when the observable part of its orbit became available again last year. Looking ahead, further observations using similar techniques may reveal additional planets within the TOI-1338/BEBOP-1 circumbinary system.
Image Source: NASA’s Goddard Space Flight Center, Chris Smith
