Astronomers have made a remarkable discovery, finding a unique exoplanet system that resembles Tatooine, the fictional home of Luke Skywalker (don’t forget to check out our Star Wars-related news). Speculation among scientists about the existence of planets orbiting twin suns has been ongoing for some time, and now their theories have become a reality.
Binary star systems, where two stars revolve around each other, are quite prevalent in the Milky Way galaxy, with nearly half of the sun-like stars being part of such systems. Until recently, only 14 circumbinary planets, which orbit both stars of a binary system, had been definitively confirmed.
The prevailing belief was that the binary stars would disrupt planetary formation due to the turbulent environment created by their gravitational interaction — however, the discovery of Kepler-16b in 2011 challenged this assumption and demonstrated the feasibility of circumbinary planet formation.
An illustration of TOI-1338b. (Image credit: NASA)
BEBOP-1c, a colossal gas giant
The most recent study focused on the binary system TOI-1338, located around 1,320 light-years away in the constellation Pictor. In 2020, NASA’s TESS space telescope detected a circumbinary planet named TOI-1338b orbiting the binary stars of TOI-1338. Although the scientists’ original intention was to determine the mass of TOI-1338b, they unexpectedly came across another planet.
This newly found celestial body has been designated as BEBOP-1c, named after the project responsible for gathering the data—Binaries Escorted By Orbiting Planets (BEBOP). BEBOP-1c is a colossal gas giant, approximately 65 times the mass of Earth yet five times lighter than Jupiter. It completes an orbit around its twin suns at a distance of roughly 79% of the average span between Earth and the sun, requiring approximately 215 days to complete a full revolution.
An artist’s concept that illustrates Kepler-16b, the first planet known to definitively orbit two stars, what’s called a circumbinary planet. (Image: “In the Light of Two Suns” by NASA Universe)
In comparison, TOI-1338b orbits its stellar counterparts at roughly 46% of an astronomical unit (AU) and has an orbital period of approximately 95 days. The estimated mass of TOI-1338b is at most 22 times that of Earth. TOI-1338b was discovered by a high school student utilizing the TESS space telescope, which observed the planet transiting in front of its brighter star on multiple occasions, allowing the researchers to estimate its size.
Unlike TOI-1338b, the detection of BEBOP-1c relied on the radial velocity technique. This method involves observing the oscillatory motion of the stars caused by the gravitational influence of orbiting planets. The discovery of BEBOP-1c solely through this technique holds great significance, as most circumbinary planets have been identified using transit observations made by expensive space telescopes like Kepler and TESS.
Its precise dimensions are still unknown
Detecting circumbinary planets using the radial velocity technique is challenging due to the interference arising from the combined light of both stars. Nevertheless, the BEBOP project concentrates on binary systems where the secondary star is notably smaller and dimmer than the primary star, minimizing interference.
Although these types of binary star systems are less prevalent, future advancements in data analysis techniques will enable the detection of planets encircling binary systems with equally sized stars. Currently, only two planets are known in the TOI-1338/BEBOP-1 system, but scientists anticipate the discovery of more in the future. Further research endeavors aim to ascertain the precise dimensions of BEBOP-1c and the mass of TOI-1338b.
Additionally, scientists plan to investigate the atmospheric chemistry of circumbinary planets and compare them to planets orbiting solitary stars, which will provide valuable insights into the process of planetary formation. The findings of this study were published in the journal Nature Astronomy on June 12th.