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Penn State astronomy doctoral student discovers Jupiter-like exoplanet migrating toward its star

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Exoplanet

A Penn State astronomy doctoral student and her team of collaborators recently detected a “migrating,” Jupiter-like exoplanet with a “highly elliptical orbit” around its star.

The gas giant planet, named TOI-3362b, is five times the mass of Jupiter and orbits its host star in 18.1 days. The planet is expected to move closer to its star, eventually becoming a “hot Jupiter” — a gas giant planet with an orbital period of less than 10 days, according to the research.

Due to its highly elliptical orbit, TOI-3362b may be experiencing rapid temperature fluctuations and extreme weather, which hasn’t been confirmed through research yet.

Jiayin Dong led the research and subsequent paper, and she discovered the planet using the "transit technique" with the Transiting Exoplanet Survey Satellite and verified it with telescopes in Australia and Chile.

“If the planet is passing in front of the star, then the brightness of the star decreases a little bit, and that’s how we know there might be a planet,” Dong (doctorate-astronomy and astrophysics) said. “This technique is called ‘transit technique.’”

Dong and her collaborators were able to determine the planet was “extremely eccentric” based on the “short duration” of its transit signal.

“The time that the planet spends passing in front of its host star is short compared to what we expected based on the planet’s orbital period,” Dong said. “This short duration implies that the planet has an elongated orbit — unlike all the planets we have in the solar system.”

While previous theories of planetary formation were based on the solar system exclusively, Dong and her collaborators said they’re trying to understand how some gas giant exoplanets are located so close to their host stars.

Traditional planet formation theories suggest gas giant planets like Jupiter and Saturn form in a cold disk of gas and debris several times the distance between Earth and the sun.

The discovery of this exoplanet suggests one possible pathway of locating gas giant planets near their stars — “high-eccentricity migration.” Dong and her collaborators said they were motivated to catch a planet while it migrated toward its star.

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“The idea that planets migrate themselves was a hypothesis,” Chelsea Huang, another author of the paper and Torres Postdoctoral Fellow at MIT Kavli Institute for Astrophysics and Space Research, said, “so it’s nice to actually catch one in the action. It is kind of a proof of concept.”

Rebekah Dawson, Shaffer Career Development Associate Professor in Science, associate professor of astronomy and astrophysics, said “orbital shrinkage” is caused by the distortion of tidal forces between the planet and its star due to the planet’s highly elliptical orbit.

She said as the planet “periodically gets very close to the star during its point of closest approach,” it gets stretched by tidal forces, and when the planet moves farther away from the star, the tidal forces “die down,” which “dissipates energy” — causing the planet's orbit to shrink.

The findings of the paper inspired Dong and her collaborators to begin developing a new planet formation theory, which is still in the works, they said.

“Now knowing how different the extrasolar system could be, we are creating a theory that could both explain the solar system and unique architectures we see in the extrasolar system,” Dong said.

Dong said she was thrilled the day she made the discovery because she was hoping to find a planet like TOI-3362b for almost two years.

“It was quite exciting,” Dong said. “This was also the first planet I discovered — that makes it special too.”

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Huang said the discovery of migrating gas giants helps astronomers understand “how unique” the solar system is and how humans are “connected to planetary systems around other stars.”

Dawson said studying systems that “aren’t habitable themselves” allows astronomers to learn about “what physics and processes” can be applied to systems that have habitable planets.

“If we find a system that is habitable, we want to be able to piece together its history,” Dawson said.

Dong and her team said they would now like to understand how prevalent highly eccentric migrating planets like TOI-3362b are.

“This is just one warm Jupiter example,” Dong said. “Our search actually yielded a sample — 40 to 50 of those. It will be very interesting to look at them as a population.”

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