3 hours ago
5
Astronomers have discovered 27 new potential planets that orbit two stars, like the fictional desert planet Tatooine from the Star Wars universe.
To date, only about 18 circumbinary planets – which orbit around two stars – had been identified in the universe. More than 6,000 planets have been discovered that orbit single stars, like Earth does around the sun.
In a timely publication for 4 May, also known as Star Wars Day, scientists have identified nearly 30 more candidate planets, whose distances range from 650 to 18,000 light years away from Earth.
“There are many things in astronomy that aren’t very tangible,” said Assoc 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 would it mean to stand on a planet with two suns”.
More than half of the stars in the universe exist in binary or multiple star systems. Scientists previously identified circumbinary planets via their transits: when these planets pass in front of a star, “it casts a shadow on the star’s surface, we see a dip in brightness of the star … and we can infer there’s something going around it,” Montet said.
But this only happens when the planet and its star perfectly align with our line of sight from Earth. “We’re missing lots of systems, potentially,” Montet said.
“Planets are hard to find. It’s like trying to see a candle right next to a big street light.”
The researchers instead used a method known as “apsidal precession”, searching for a wobble between stars that orbit around and eclipse each other.
“If we monitor the exact timing of these eclipses… that can tell us that there’s something else going on in the system,” said Margo Thornton, the study’s lead author and a PhD candidate at UNSW.
After eliminating other factors such as the rotation and gravitational pull of the two stars, the team identified 36 star systems out of 1,590 whose behaviour could only be explained by a third body.
For “27 of those objects, it is possible that they are planet mass”, Thornton said. More research into their spectra – the light they emit – was needed to formally confirm them as circumbinary planets, she said. “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?”
The team discovered the potential planets – which likely range from Neptune-sized to ten times heavier than Jupiter – using data from Nasa’s Transiting Exoplanet Survey Satellite, a planet-hunting space telescope that launched in 2018.
Dr Sara Webb, an astrophysicist at the Swinburne University of Technology who was not involved in the research, said the team’s “very clever techniques” could be used to find more planet candidates in the future.
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.”
“When the original Star Wars was released, we didn’t know that there were exoplanets [planets outside our solar system] at all.”
“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 was published in the Monthly Notices of the Royal Astronomical Society.
