A high school student made a remarkable discovery just after starting an internship with NASA: a planet orbiting two stars.

Last summer, Wolf Cukier, had just completed his junior year at Scarsdale High School in New York when he joined NASA’s Goddard Space Flight Center in Greenbelt Maryland for a summer internship. NASA assigned him to look at star brightness variations that had been recorded by the space program’s Transiting Exoplanet Survey Satellite (TESS), which aims to find planets outside the Earth’s solar system.

About three days into his internship, Cukier noticed a signal from a system named “TOI 1338.”

“I was looking through the data for everything the volunteers had flagged as an eclipsing binary, a system where two stars circle around each other and from our view eclipse each other every orbit,” Cukier said, according to NASA, which announced the discovery last week. “At first I thought it was a stellar eclipse, but the timing was wrong. It turned out to be a planet.”

The planet was dubbed “TOI 1338 b,” and scientists determined it was the first “circumbinary planet” discovered by the satellite — a world which orbits two stars. Cukier has co-authored a paper on the discovery with scientists from the Center as well as San Diego University, the University of Chicago and elsewhere. On Monday, their findings were presented at the 235th American Astronomical Society meeting in Honolulu.

TOI 1338 b, which is about 6.9 times bigger than the Earth, is located in the TOI 1338 system about 1,300 light years away. It orbits in a close plane to the stars, so it experiences frequent solar eclipses, according to NASA.

To learn about these and other stars, TESS’s four cameras each take an image of the sky for 30 minutes every 27 days. Scientists then measure how the brightness of each star changes over time.

However, it’s more challenging to detect planets orbiting two stars. TOI 1338 b “transits” — when a planet moves in front of its star from the Earth’s perspective — vary between 93 and 95 days because of the way the stars orbit. The satellite can see the transit of the bigger star, which is 10% bigger than the Earth’s Sun, but not the smaller, dimmer star, which is only about one-third of the Sun. Scientists are more likely to find bigger planets, because smaller bodies have a lesser effect on the brightness of a star during their transit.

Algorithms “really struggle” with these kinds of signals, said Veselin Kostov, the lead author of the study and a scientist Goddard and the SETI Institute.

“The human eye is extremely good at finding patterns in data, especially non-periodic patterns like those we see in transits from these systems,” Kostov said.

NASA’s Kepler and K2 missions previously found 12 circumbinary planets in 10 systems, according to NASA.

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