Inspired by writer Liu Cixin, Chinese scientists spot signals from real-world ‘three-body’ star system
- Phenomenon popularised by science fiction writer Liu Cixin is common in our galaxy but hard to study
- Research sheds light on complex behaviour of three stars that can be seen at the head of the constellation Orion
The scientists – from Hangzhou Dianzi University, the Chinese Academy of Sciences and China Three Gorges University – used Nasa observation data to look for periodic changes in the brightness of the three stars, collectively known as GW Ori.
The resulting study, published in the peer-reviewed journal Science China Physics, Mechanics & Astronomy, offers key evidence for the geometric structure and evolution of the triple-star system, according to lead researcher Tian Haijun.
Liu’s novel is based on a physics problem which many scientists believe is insoluble – how to predict the motion of three bodies in relation to each other, when a system of more than two bodies quickly becomes chaotic.
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Tian, from Hangzhou Dianzi University, and his colleagues studied data from Nasa’s Transiting Exoplanet Survey Satellite (TESS) to track the GW Ori system, made up of two stars orbiting each other while a third, more distant star, orbits the pair.
“For the first time, we were able to spot two short-term signals and precisely measure the rotational periods of the pair, which are about two and three days,” he said.
“Such fast rotations are typical for very young stars and different from our sun, which rotates every 25 days.”
A multiple star system forms when an enormous molecular cloud collapses under gravity, giving birth to two or more stars. The “leftover materials” might evolve into planets, Tian said.
But all objects in such a system are intricately intertwined by gravity – leading to the complex interactions at the heart of the three-body problem.
“Their movements and interactions could become so complex that if life ever existed there, it could have been destroyed and reborn many times,” Tian said.
Multiple star systems are the rule rather than the exception in the galaxy, where our solar system – eight planets orbiting a solitary sun – is not a common phenomenon, according to Tian. More than half of the stars have one or more partners, he said.
“While such systems are notoriously hard to observe, we expect to use more advanced telescopes, including the upcoming China Space Station Telescope (CSST), to better understand how they form and behave.”
Tian and his colleagues are looking forward to conducting more precise measurements of the GW Ori system once the CSST is operational in low-Earth orbit.
The telescope will be equipped with an instrument known as the Integrated Field Spectrometer, which has very high spatial resolution.
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“The space telescope will be a useful tool for astronomers around the world to understand the formation and evolution of fascinating multiple star systems such as GW Ori,” Tian said.
The GW Ori system, believed to be only 1 million years old, has been previously studied by scientists using telescopes such as the Atacama Large Millimetre Array in Chile.
Previous research has shown that all three stars are slightly heavier than the sun. The system also contains a gigantic disk where new planets might be forming.
Tian’s team conducted detailed analysis of three months’ worth of TESS data showing the GW Ori system’s light curves. They found two signals with periods of 3.02±0.15 days and 1.92±0.06 days, respectively.
After ruling out eclipses and other possibilities, the researchers concluded the signals probably originated from the rotation of star spots – just like the sun’s black spots – on the surface of the binary stars GW Ori A and B.
“We also ruled out the possibility of ‘man-made factors’, because the formation of life took at least hundreds of millions of years here on Earth, and the GW Ori system is too young for that,” Tian said.
The researchers also calculated the inclination of the stars and found that the rotation planes of GW Ori A and B are almost parallel with their orbital plane as a binary.
“This means that the geometry and operation mode of the binary system are relatively simple,” Tian said.
