An international team of astronomers has identified two giant, low-density exoplanets orbiting the young star HD 114082. The discovery, detailed in The Astrophysical Journal Letters, marks the longest-period transiting exoplanets ever found around such a young star, providing critical data on how planetary systems evolve in their early stages.
A Rare Look at Planetary Formation
Instituto de Astrofísica Canarias
Located approximately 311 light-years from Earth, the HD 114082 system offers a unique window into the infancy of solar systems. While the Sun is roughly 4.5 billion years old, the host star in this system is only about 15 million years old. According to researchers at the Universidad de La Laguna (ULL) and the Instituto de Astrofísica de Canarias (IAC), this star is significantly more luminous and hotter than our Sun, spinning 15 times faster with 28% more mass.
The study of these two gas giants, designated HD 114082 b and HD 114082 c, helps astronomers contextualize the early development of planetary orbits. The planets orbit their host star in a region where they receive about 200 times more light and heat than Jupiter does from the Sun. By separating the faint planetary signals from the intense stellar activity, the research team was able to determine the characteristics of these worlds, which are notable for their unusually low density.
Orbital Dynamics and the Tug-of-War
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The two planets exhibit characteristics that define them as “puffy” exoplanets, a term used for gas giants with very low atmospheric density. The inner planet, HD 114082 b, is approximately the size of Jupiter and orbits 20% closer to its star than Earth does to the Sun. The outer planet, HD 114082 c, sits at an orbital distance similar to Earth’s and possesses a radius 36% larger than Jupiter.
The research, led by Carlos del Burgo Díaz, highlights a complex gravitational relationship between the two bodies. The planets are locked in an orbital resonance, meaning their periods have a simple whole-number relationship that results in a gravitational interaction. As noted by Alejandro Suárez Mascareño, a coauthor of the paper, this interaction manifests as a gravitational tug-of-war.
“The planets move in almost circular orbits in the same plane, and may be in or near a resonance [which implies that the planetary orbital periods have a simple whole-number relationship].”Alejandro Suárez Mascareño, ULL/IAC
Detection Through Transit Methods
TESS Finds Related Stars Have Young Exoplanets
Detecting long-period planets is notoriously difficult because the drop in starlight—the transit—is rare and small. Astronomers utilized a suite of international facilities to confirm these findings, including the Transiting Exoplanet Survey Satellite (TESS), the CHaracterising ExOplanet Satellite (CHEOPS), and ground-based observatories such as the Next-Generation Transit Survey (NGTS) in Chile and the ASTEP+ telescope in Antarctica.
The team successfully mapped four non-consecutive dips in light for the inner planet, allowing for a precise orbital period calculation. The outer planet’s period, estimated at 314 days with a margin of error of about 9 percent, was determined from a single confirmed transit supplemented by additional measurements. The researchers emphasized the rarity of identifying such long-period bodies while they are still in their youth.
“We have identified a strange pair of giant exoplanets. 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 the 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.”Carlos del Burgo Díaz, Universidad de La Laguna (ULL) and Instituto de Astrofísica de Canarias (IAC)
Future Observations and Scientific Stakes
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The discovery has set the stage for follow-up observations. Because the orbital period of the outer planet was identified based on a single transit, the scientific community is now monitoring the system for a second transit. Pinpointing this period with absolute precision remains a primary objective for the researchers.
This work underscores the value of continued monitoring of young stellar systems. As astronomical archives and modern space telescopes continue to provide long-term data on light curves, the ability to characterize such “puffy” giants improves. By understanding how these gravitational interactions influence the orbits of planets within their first few million years, scientists hope to gain a clearer picture of how solar systems—including our own—eventually stabilize into the configurations observed today.
