In a discovery fitting for Star Wars Day, astronomers have identified 27 new potential planets that orbit two stars, reminiscent of the fictional desert world Tatooine from the Star Wars franchise. The findings, published in the Monthly Notices of the Royal Astronomical Society, more than double the number of known candidate circumbinary planets—worlds that circle a pair of stars.
What Are Circumbinary Planets?
Circumbinary planets are those that orbit two stars, unlike Earth, which orbits a single star. Before this study, only about 18 such planets had been confirmed, while over 6,000 exoplanets orbiting single stars have been discovered. The new candidates range in distance from 650 to 18,000 light-years from Earth.
“There are many things in astronomy that aren’t very tangible,” said Associate Prof Ben Montet of the University of New South Wales (UNSW), the study’s senior author. “But thanks to the famous Tatooine sunset scene in the first Star Wars film, everyone has a picture of what a circumbinary planet looks like and what it would mean to stand on a planet with two suns.”
How Were They Found?
Traditional methods of finding circumbinary planets rely on detecting transits—when a planet passes in front of its star, causing a slight dip in brightness. However, this requires precise alignment with Earth’s line of sight, meaning many planets are missed. “It’s like trying to see a candle right next to a big street light,” Montet explained.
The research team, led by PhD candidate Margo Thornton from UNSW, used a different technique called apsidal precession. This method monitors the timing of eclipses in binary star systems. “If we monitor the exact timing of these eclipses … that can tell us that there’s something else going on in the system,” Thornton said. By ruling out other factors like stellar rotation and gravitational interactions, the team identified 36 star systems out of 1,590 that showed signs of a third body. Of these, 27 are likely planetary in mass.
What Are These Planets Like?
The potential planets are estimated to range in size from Neptune-like to up to ten times the mass of Jupiter. Confirming them as circumbinary planets will require further analysis of their spectra—the light they emit—to determine their exact mass and nature. “It’s just a matter of: what is the mass of it? Is it a planet? Is it a brown dwarf? Is it a star?” Thornton said.
Dr Sara Webb, an astrophysicist at Swinburne University of Technology not involved in the study, praised the team’s “very clever techniques,” which could be used to find more planet candidates in the future. She noted that circumbinary planets likely have “very extreme environments” unlike anything in our solar system, but “a planet like Tatooine could potentially exist where there is that sweet spot between its orbit of the two stars—where it’s not too hot and it’s not too cold.”
Implications and Future Research
The discovery highlights how science fiction can inspire real scientific breakthroughs. “When the original Star Wars was released, we didn’t know that there were exoplanets at all,” Webb said. “A lot of things that are predicted in art and in artistic concepts of what the universe might be, we tend to find it … in science as well.”
The data for this study came from NASA’s Transiting Exoplanet Survey Satellite (TESS), a space telescope launched in 2018. With more than half of all stars existing in binary or multiple systems, the team’s method could unlock a treasure trove of new worlds.
