Circumbinary systems are those in which the planets orbit around two suns, and this is the second to have more than one planet

An international team of astronomers led by researchers from the University of Birmingham (UK) has announced the second-ever discovery of a multi-planetary circumbinary system, similar to the mythical Tatooine, the home planet of Luke Skywalker in Star Wars. as published in the journal Nature Astronomy.

Circumbinary systems contain planets that orbit two stars in the center, instead of just one, as in our Solar System. These planets orbit both stars at the same time. The newly discovered planet is called BEBOP-1c, after the name of the project that collected the data. BEBOP stands for Binaries Escorted By Orbiting Planets. The BEBOP-1 system is also known as TOI-1338.

That planet was discovered using the transit method and attracted attention because it passed in front of the brighter of the two stars on several occasions.

«”The transit method allowed us to measure the size of TOI-1338b, but not its mass, which is the most important parameter of the planet,” explains Dr Matthew Standing, lead author of the study, who received his PhD from the University of Birmingham and he is now a researcher at the Open University

The BEBOP team was already monitoring this system using another detection method at the time, called the Doppler method. This method, also called wobble or radial velocity, is based on the precise measurement of the speed of stars. “This is the same method that led to the first detection of exoplanets, for which Mayor and Queloz received the Nobel Prize in 2019,” explains Matthew’s then-supervisor, Amaury Triaud, a professor at the University of Birmingham. Using state-of-the-art instruments installed on two telescopes located in the Atacama desert in Chile, the team attempted to measure the mass of the planet observed by TESS. Despite their efforts and years of work, the team was unable to achieve this, but instead discovered a second planet, BEBOP-1c, and measured its mass.

So far only 12 circumbinary systems are known, and this is the second to host more than one planet,” says David Martin, an astronomer and Sagan Fellow at Ohio State University in the United States.

“BEBOP-1c has an orbital period of 215 days and a mass 65 times that of Earth, which is about five times that of Jupiter,” Standing adds. This was a difficult system to confirm, and our observations were interrupted by the covid pandemic, when the telescopes in Chile closed for six months during a critical part of the planet’s orbit. This part of the orbit was not observable again until last year, when we finished the detection,” he says.

At the moment, only two planets are known in the TOI-1338/BEBOP-1 circumbinary system, but more could be identified in the future, with observations similar to those made by the team. Although rare, circumbinary planets are important in advancing our understanding of what happens when a planet is created. “Planets are born in a disk of matter that surrounds a young star, where the mass progressively accumulates to form planets,” explains Dr Lalitha Sairam, a researcher at the University of Birmingham and second author of the study. “In the case of circumbinary geometries, the disk surrounds both stars,” he continues. Since both stars orbit each other, they act like a giant shovel that disturbs the disk near them and prevents planet formation, except in quiet regions far from the binary. It is easier to pinpoint the location and conditions for planet formation in circumbinary systems than in individual stars like the Sun.”

The team does not yet know the size of BEBOP-1c, only its mass, however the researchers will now try to use the transit method to measure the size of BEBOP-1c.

source: https://www.nature.com/articles/s41550-023-01948-4