Exoplanet Found by TESS Orbiting a Pair of Stars Like Tatooine

The Cosmic Companion
Jan 8 · 3 min read

NASA’s Transiting Exoplanet Survey Satellite (TESS) spies a planet with a pair of suns, similar to the home world of Luke Skywalker from Star Wars. In future years, 100 more planets like this world may be found.

Roughly 1,300 light years from Earth, in the direction of the constellation Pictor, sits TOI-1338, a solar system containing a pair of suns. Now, a new discovery reveals a world orbiting these binary stars, much like the desert planet Tatooine from Star Wars.

The Transiting Exoplanet Survey Satellite (TESS) observatory spotted a previously-unseen planet, dubbed TOI-1338 b, orbiting within the binary star system. This marks the first time TESS has found a planet in a system containing a pair of stars.

A simulation showing how KOI-1338 may look as it orbits its pair of suns. Image credit: Screenshot from video created by NASA Goddard.

This newly-discovered world is thought to contain roughly 6.9 times the mass of Earth — larger than Neptune, but smaller than Saturn. As TOI-1338 b orbits the pair of stars once every 95 days, it regularly blocks out a portion of the light coming from the brighter star. By measuring how much light is blocked during these passages, astronomers are able to determine the size of the planet.

The larger of the two stars is roughly 10 percent larger than the Sun, while the smaller, cooler partner contains around one-third as much mass as our parent star.


My Two Suns

Circumbinary planets — those orbiting two stars — can maintain stable orbits if they orbit close enough to one of the parent bodies, or if the stars orbit closely to each other while the planet circles the stellar pair (as is the case in the KOI-1338 system). A dozen of these worlds were discovered by the planet-hunting Kepler spacecraft, and NASA hopes to find as many as 100 more using TESS.

If TESS, launched in 2018, is able to find scores of new circumbinary planets, the data obtained will allow the first statistical analysis of this little-understood class of exoplanet.


Finding a World in the Darkness

The transit of this world was first spotted by Wolf Cukier, a high school student from Scarsdale High School in Syracuse, NY, working at NASA.

“About three days into my internship, I saw a signal from a system called TOI 1338. At first I thought it was a stellar eclipse, but the timing was wrong. It turned out to be a planet,” Cukier said.

The team behind this discovery also announced their confirmation of another similar world, KOI-3152 b.

“We first noted convincing evidence for this planet in 2012, but confirmation required additional data and improvements in computer modeling. In particular, star spots on the primary host star and a weak eclipse signal from the second star made the analysis difficult,” William Welsh, an astronomer at San Diego State University, stated.

“A desert planet on the Outer Rim, Tatooine is dusty, gritty, and grim.
Everything’s parched and thirsty and dry, from the searing earth to the glaring sky. It’s those two blasted suns, All round and white-hot.
They’re to blame for this heat… But, oh, what a shot!”
― Calliope Glass, Star Wars OBI-123: A Book of Numbers

NASA looks at the discover of KOI-1338 b, the first circumbinary planet discovered by TESS. Video credit: NASA Goddard.

The orbit of KOI-1338 b is expected to remain stable for the next 10 million years. However, the angle of the orbit migrates over time, and starting in November 2023, the planet will not pass in front of its star, as seen from Earth, for another eight years.

Most stellar systems contain two or more stars, and although it is more difficult to detect worlds around these systems than those in solar systems with just a single sun, we may soon find worlds like Tatooine may be more common in the Universe than they were in Star Wars.


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Writing about space since I was 10, still not Carl Sagan. Mailing List/Podcast: https://thecosmiccompanion.substack.com

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