Longest-period young transiting exoplanets discovered

It’s 2234, you’re on your annual class field trip touring exoplanets, and your teacher informs everyone they can pick one more exoplanetary system to explore before heading back to Earth. You and your classmates are exhausted from the day’s activities and you’re hungry. However, you get really excited because you already know what everyone will want. You and your classmates all shout in unison, “The young and far away puffy ones!”

This fictionalized tale describes HD 114082 b and HD 114082 c, which are two gas giant exoplanets located approximately 311 light-years from Earth and are the topic of a recent study published in The Astrophysical Journal Letters. While gas giant exoplanets are incredibly common, these two gas giants exhibit unique characteristics.

Specifically, the orbital periods of HD 114082 b and HD 114082 c are approximately 225 and 314 days, respectively. However, the researchers note the latter has a margin of error of about 9%. Additionally, both exoplanets and their star are incredibly young, with their star being only about 15 million years old. For context, our sun is approximately 4.5 billion years old.

One of the most fascinating aspects of this study is that both exoplanets were examined using the transit method, which is when astronomers measure a brief drop in starlight when an exoplanet passes directly in front of it. Additionally, both exoplanets are locked in what’s known as an orbital resonance, meaning for each single orbit of one exoplanet, the other exoplanet might orbit twice. The researchers note this resonance causes each exoplanet to perform a sort of gravitational tug-of-war.

The highlight of the study was that these two exoplanets are the longest-period transiting exoplanets discovered to date. While the transit method has been incredibly effective at detecting exoplanets with short periods of hours or days, detecting longer-period exoplanets of several months becomes incredibly difficult since the drop in starlight is much smaller due to the large distance the exoplanet is from their star. While both exoplanets are approximately the size of Jupiter, their atmospheres have very low density, which astronomers often refer to as “puffy” exoplanets.

“We have identified a strange pair of giant exoplanets,” said Dr. Carlos del Burgo Díaz, who is a Beatriz Galindo Senior distinguished researcher at the Universidad de La Laguna (ULL) and Instituto de Astrofísica de Canarias (IAC) and lead author of the study. “They stand out among the youngest detected by passing in front of their star because they take longer to complete an orbit. The inner planet, 20% closer to its star than Earth is to the sun, has Jupiter’s size. The outer planet is at the same orbital distance as Earth, and has a radius 36% larger than that of Jupiter and a mean density more than 7.5 times less than that of water, so it would float on it.”

Both exoplanets were examined using a combination of data obtained from space- and ground-based telescopes operated by NASA, the European Space Agency, non-profit agencies, academia, and government consortiums. While HD 114082 b was discovered in 2022, this study discovered HD 114082 c, and combining data from the various telescopes helped provide estimates for both of their masses, radii, and orbital distances.

Despite the extremely young age of the star compared to our sun, the researchers hypothesize that both exoplanets formed farther out within the protoplanetary disk of gas and dust and later migrated inward. Therefore, the HD 114082 system could be used as an analog for better understanding young star systems, specifically the formation and evolution of young planets.

Going forward, the researchers discussed several potential directions for future research regarding these two exoplanets, including providing a tighter estimate on the orbital period of HD 114082 c, using NASA’s James Webb Space Telescope to analyze the atmospheres of both exoplanets, and learning more about their gravitational tug-of-war.

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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