In a move that would make Luke Skywalker feel slightly less special, astronomers have discovered 27 potential new planets that orbit two stars - just like the fictional desert world of Tatooine. The timing, naturally, coincides with 4 May, aka Star Wars Day, because the universe has a sense of humour.
To put this in perspective, only about 18 circumbinary planets - that's science-speak for planets orbiting two stars - had been identified before. Meanwhile, Earth and its 6,000-plus single-star-orbiting brethren are starting to look a bit pedestrian. These new candidates, ranging from 650 to 18,000 light years away, suggest we've been missing a lot of the cosmic party.
“There are many things in astronomy that aren’t very tangible,” said Associate Professor Ben Montet of the University of New South Wales, the study's senior author. But thanks to that iconic Tatooine sunset in Star Wars, “everyone has a picture of what a circumbinary planet looks like and what would it mean to stand on a planet with two suns.” Finally, a scientific concept that doesn't require a PhD to visualise.
The usual method of finding these planets - watching for a dip in starlight when a planet transits - only works if everything aligns perfectly with Earth. “We’re missing lots of systems, potentially,” Montet admitted. “Planets are hard to find. It’s like trying to see a candle right next to a big street light.”
So the team, led by PhD candidate Margo Thornton at UNSW, used a cleverer trick called “apsidal precession” - basically, they looked for a telltale wobble in stars that orbit and eclipse each other. “If we monitor the exact timing of these eclipses… that can tell us that there’s something else going on,” Thornton said. After ruling out star rotation and gravity, they found 36 star systems out of 1,590 that needed a third body to explain their behaviour. For 27 of those, that third body is likely a planet.
These potential planets, which probably range from Neptune-sized to ten times heavier than Jupiter, were spotted using data from NASA's Transiting Exoplanet Survey Satellite (TESS), a space telescope that's been hunting planets since 2018. Dr Sara Webb, an astrophysicist at Swinburne University of Technology not involved in the research, praised the team's “very clever techniques” and suggested they could unearth even more candidates.
Circumbinary planets would likely have “very extreme environments” unlike anything in our solar system, Webb said, 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.” She also noted that when the original Star Wars was released, we didn't even know exoplanets existed. “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 research, published in the Monthly Notices of the Royal Astronomical Society, reminds us that sometimes science fiction is just science that hasn't happened yet.