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This exoplanet has two suns – just like Tatooine

A team of astronomers has detected a “Tatooine-like” exoplanet that orbits two stars. A person living on the planet would see two suns in the sky, like Luke Skywalker’s home planet in Star Wars — but unfortunately, it’s a gas giant, so don’t make any plans to build a house there.

The planet, known as Kepler-16b, is located 245 light-years away and was detected using a ground-based telescope at the Observatoire de Haute-Provence in France. A planet orbiting two stars is technically known as a circumbinary planet, and these are rarely discovered. They are interesting puzzles as it’s not clear how such planets form. Typically, planets form from disks of matter around a single star, called protoplanetary disks, but this might not work in a system with two stars.

Artist's impression of Kepler-16b, which can be seen in the foreground.
Artist’s impression of Kepler-16b, the first planet known to definitively orbit two stars – what’s called a circumbinary planet. The planet, which can be seen in the foreground, was discovered by NASA’s Kepler mission. NASA/JPL-Caltech/T. Pyle

“Using this standard explanation it is difficult to understand how circumbinary planets can exist,” leader of the team, Amaury Triaud of the University of Birmingham, explained in a statement. “That’s because the presence of two stars interferes with the protoplanetary disc, and this prevents dust from agglomerating into planets, a process called accretion. The planet may have formed far from the two stars, where their influence is weaker, and then moved inwards in a process called disc-driven migration – or, alternatively, we may find we need to revise our understanding of the process of planetary accretion.”

Another notable feature of the planet is the way that it was detected. The planet was first discovered by the space-based telescope Kepler in 2011, but these researchers detected the planet using the radial velocity method, which used a ground-based telescope to look at the tiny variations in the star caused by the gravity of the planet orbiting around it. Detecting such planets from a ground-based telescope using this method is much cheaper than using space-based telescopes like Kepler, so it opens the door to discovering more planets like it in the future.

“Our discovery shows how ground-based telescopes remain entirely relevant to modern exoplanet research and can be used for exciting new projects,” said Dr. Isabelle Boisse of Aix-Marseille University. “Having shown we can detect Kepler-16b, we will now analyze data taken on many other binary star systems, and search for new circumbinary planets.”

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