Two puffy giant exoplanets set the record for longest orbital periods detected around a young star

An international team of astronomers has confirmed the longest-period transiting exoplanets ever found orbiting a young star. The two gas giants, both circling the star HD 114082 at roughly 311 light-years from Earth, take between 225 and 314 days to complete a single orbit — a timescale that makes their detection by the transit method a remarkable observational achievement. The study, published in The Astrophysical Journal Letters, was led by Dr. Carlos del Burgo Díaz of the Universidad de La Laguna (ULL) and the Instituto de Astrofísica de Canarias (IAC), with contributions from 38 researchers across three continents.

A star that is barely a teenager by cosmic standards

The host star, HD 114082, is an F-type star and in several respects an intensified version of our Sun. It carries roughly 28 percent more mass, rotates about 15 times faster, burns approximately 1,000 degrees hotter at its surface, and shines with nearly four times the luminosity. Its two known planets receive around 200 times more stellar radiation than Jupiter does from the Sun.

What makes this system genuinely extraordinary, however, is its age. HD 114082 is only 15 million years old. For comparison, our Sun has been burning for approximately 4.6 billion years, which means this star has existed for just 0.3 percent of that span. Astronomers studying HD 114082 are examining a planetary system at a developmental stage so early that it offers a direct window into processes that, in our own solar system, concluded billions of years before humans arrived.

Two planets, two records, one gravitational dance

The inner planet, HD 114082 b, orbits with a period of 225.5504 days, determined to the minute through four separate transit events observed across multiple years and facilities. It is roughly the size of Jupiter and sits about 20 percent closer to its star than Earth is to the Sun. Its companion, HD 114082 c, completes one orbit in approximately 314 days — with an estimated uncertainty of around nine percent, since only a single confirmed transit has been captured — placing it at roughly the same orbital distance from its star that Earth occupies in our own solar system. This outer world carries a radius about 36 percent larger than Jupiter’s and a mean density more than 7.5 times lower than that of liquid water. In plain physical terms: it would float.

Together, the two planets represent the longest-period young transiting exoplanets ever identified. Detecting long-period transits is inherently difficult. As a planet orbits farther from its host star, the brightness dip it produces during transit becomes shallower, rarer, and harder to separate from the variability of the star itself. Assembling the full observational picture required data from NASA’s TESS space telescope, ESA’s CHEOPS satellite, the ground-based NGTS array operating in Chile, and the ASTEP+ telescope stationed in Antarctica — an integration of infrastructure that reflects both the complexity of the detection and the ambition of the collaboration.

Puffy giants inside a debris disc

Both planets belong to the category known informally as puffy giants. Their physical radii are comparable to or larger than Jupiter’s, yet their masses are a fraction of what those sizes might suggest. HD 114082 c has a maximum estimated mass of around 24 percent of Jupiter’s, roughly equivalent to 4.4 times the mass of Neptune. This pairing of large radius and low mass produces the extreme low densities that characterize the puffy giant class, and both planets appear to retain enormously expanded atmospheric envelopes that gravity has not yet finished contracting — a clear signature of their youth.

The two planets also appear to be engaged in a gravitational coupling near an orbital resonance, meaning their orbital periods approach a simple integer ratio. This near-resonance causes each planet to subtly delay or advance the transit time of the other in a measurable way, providing a route to estimating their masses even without spectroscopic radial velocity measurements. It also points toward a shared dynamical history that has kept their orbits nearly circular and coplanar since formation.

Beyond the planets themselves, the HD 114082 system contains a debris disc — the dusty remnant of the protoplanetary material from which the planets formed. The inner portion of this disc lies in the same plane as the planetary orbits, likely sculpted over time by the gravitational influence of the two giants. The outer belt, by contrast, appears inclined relative to that plane, suggesting a more primordial structure that the planets have not yet fully perturbed.

What this system tells us about how planets form

The leading formation scenario for HD 114082 b and c involves the gradual accumulation of material within the protoplanetary disc, followed by runaway gas accretion and, potentially, inward migration from a colder, more distant birthplace. In situ formation, however, cannot be ruled out. In either case, the system provides a snapshot of planetary evolution at a moment when most young planetary systems remain too complex and dynamically noisy to study cleanly through the transit method.

The research team expects the broader exoplanet community to pursue a second transit detection for the outer planet, which would allow its orbital period to be pinned down with far greater confidence. From there, multiple mid-transit timing measurements for both worlds would refine their masses and potentially reveal additional bodies in the system. The James Webb Space Telescope is a natural candidate for atmospheric characterization, given that the low densities and extreme youth of both planets make them ideal targets for transmission spectroscopy.

A planetary system this young, this accessible, and this well-configured for long-period transit science occupies a distinctive position in the current exoplanet census. HD 114082 now stands not only as a record holder, but as one of the most instructive laboratories available for understanding how systems resembling our own come into existence.

Source: del Burgo, C. et al. «The longest-period young transiting exoplanets — A duo of puffy giants inside a debris disc.» The Astrophysical Journal Letters, 2026. DOI: 10.3847/2041-8213/ae63bd

© 2026 SKYCR.ORG | Homer Dávila Gutiérrez, FRAS. All rights reserved. Total or partial reproduction without express authorization is prohibited. More information The Astrophysical Journal Letters (2026). DOI: 10.3847/2041-8213/ae63bd