Astronomers Discover Unique Exoplanet Orbiting Twin Stars

A team of astronomers has made a groundbreaking discovery of a unique exoplanet, designated HD 143811 AB b, which orbits two stars in a binary system. This planet, located approximately 446 light-years from Earth, has been likened to the fictional home of Luke Skywalker in Star Wars, Tatooine, due to its dual suns. The findings were published in the journal Astronomy & Astrophysics.

Researchers from Northwestern University in Chicago, Illinois, shared a time-lapse video that captures the planet’s orbit around its twin stars. Notably, HD 143811 AB b is positioned closer to its suns than any previously observed binary star system exoplanet, providing a unique opportunity for scientists to analyze its trajectory and the dynamics of the star system.

According to Jason Wang, an expert in exoplanet imaging and a member of the research team, “Of the 6,000 exoplanets that we know of, only a very small fraction of them orbit binaries.” He emphasized the significance of capturing direct images of both the planet and its binary stars, stating, “It’s the only type of planetary system where we can trace both the orbit of the binary star and the planet in the sky at the same time.”

Despite being relatively close to its suns, HD 143811 AB b is still about 80 times farther from its stars than Earth is from the Sun. This distance means it takes approximately 300 years for the planet to complete one revolution around its twin suns, which themselves orbit each other every 18 days. The planet is also significantly larger than Jupiter, measuring roughly six times its size.

Interestingly, the discovery of HD 143811 AB b is not entirely new. The planet was identified in archival data collected a decade ago by the Gemini South telescope using its Gemini Planet Imager (GPI). Wang and his colleagues revisited this data, which included observations from 2016 and 2019, and cross-referenced it with information from the W.M. Keck Observatory. They were surprised to find a faint dot moving in conjunction with a star, indicating it was indeed a planet.

Wang explained the importance of tracking the movement of celestial bodies. “If a planet is bound to a star, then it will move with the star,” he noted. “Sometimes, when we revisit a ‘planet,’ we find it’s not moving with its star. Then, we know it was just a photobombing star passing through.” The confirmation of HD 143811 AB b as a planet was also corroborated by astronomers from the University of Exeter in the UK.

Among the intriguing characteristics of this exoplanet, scientists have noted that it reaches temperatures of approximately 1,416°F, nearly twice as hot as Venus. The planet is estimated to be around 13 million years old, which is relatively young in cosmic terms, especially when considering that Earth formed around 4.6 billion years ago.

Despite the exciting discoveries, the formation of this planet around its twin stars remains a mystery. Wang stated, “Exactly how it works is still uncertain. Because we have only detected a few dozen planets like this, we don’t have enough data yet to put the picture together.” The research team aims to continue monitoring the orbits of HD 143811 AB b and its binary stars to gain more insights into the interactions between binary stars and their orbiting planets.