Two of the Longest-Period Young Transiting Exoplanets in the HD 114082 System ✛
Context
Studying young exoplanets is crucial for testing planet formation models. In early epochs (less than 100 million years), planets still retain accretion heat, and their radii can be inflated, making them 'puffy.' The transit method, advanced by missions like the one launched by William Borucki (the visionary behind Kepler), allows us to measure planet radii, while spectroscopy determines masses via radial velocities. However, strong stellar activity in young stars complicates such measurements. The star HD 114082, an F-type star about 15 million years old in the Scorpius–Centaurus OB association, challenges standard methods with its rapid rotation and hot atmosphere, composed mostly of hydrogen and helium — a fact first firmly established for stars by Cecilia Payne-Gaposchkin. The discovery of two transiting giant planets with record-long periods opens a window into a previously inaccessible parameter space.
Methods
To determine the orbits and properties of the planets, photometric data from space telescopes TESS and CHEOPS, along with ground-based surveys NGTS, ASTEP+, and the LCO network, were used. The key challenge was distinguishing the true orbital period of planet b from its alias (pseudo-period) due to rare transits. With strategic observations at predicted times and the use of transit method, supplemented by high-resolution spectroscopy (FEROS and HARPS), the periods were reliably determined. The spectra measured the star's radial velocities, where planet signals were sought, taking into account correlations with the bisector of the cross-correlation function to filter out activity-induced false signals. Spectral lines of hydrogen, such as the Balmer series, were used for calibration and analysis.
Results
Modeling data with Gaussian processes and Bayesian inference showed planet b has a radius of 1.046 ± 0.014 $R_J$ and a period of 225.5504 ± 0.0004 days, while planet c has 1.36 ± 0.03 $R_J$ and 314 (+11/-18) days. Upper mass limits (95% confidence) are 1.6 $M_J$ for b and 2.0 $M_J$ for c, implying low densities — less than 1.7 and 1.0 g/cm³ respectively. The orbits are nearly circular and coplanar, inclined about 89.8° to the line of sight. The system also contains a debris disk, including a warm inner belt (possibly analogous to the asteroid belt) and a cold outer belt (analogous to the Kuiper Belt). Dust particles in the disk likely originate from destructive collisions of comets and asteroids. The location of the water snow line, where water condenses into ice, may have played an important role in forming these helium-hydrogen giants.
Implications
The discovery of this pair fills a gap in exoplanet demographics: so far, very little was known about young gas giants on wide orbits. Existing formation models suggest giant planets can be born beyond the snow line and migrate inward, but the details remained unclear. The observed configuration — planets in near-resonant orbits, tilted about 7° relative to the outer disk — indicates dynamical interaction that may have shaped the system's architecture. This allows linking properties of exoplanets with dusty cometary structures.
Future development
Future observations, particularly with high-resolution spectroscopy on new instruments like ANDES at the ELT, will refine planet masses and possibly detect atmospheric lines of hydrogen and helium. Continued transit monitoring will refine periods and reveal possible transit timing variations (TTV), providing independent mass estimates. Studying these planets at a 'teenage' age will help understand how quickly gas giants cool and contract. The distribution of water and other volatiles in the disk will also be investigated to reconstruct the formation history.
Impact
The results will influence models of exoplanetary system formation, the theory of debris disk dynamical evolution, and the atmospheric physics of young giants.
Next steps
Next steps include precisely determining planet c's period with additional transits, TTV analysis for independent planet weighing, and deep spectroscopic study of the atmospheres.
Key open problems
Connection to unsolved problems: The HD 114082 system is directly relevant to questions of giant planet formation and migration. It may clarify the 'puffy' planet paradox — why some gas giants have radii larger than predicted by cooling models. The observed resonant pattern also ties into the long-standing problem of planetary system stability and the role of cometary bombardment in delivering water to inner planets.
The knowledge machine's view
This section is addressed to the author of the paper and their colleagues. Neighbouring works were found by meaning-based search across our archive, not by word overlap. We do not review: we show the field around the work.
What the work does
The study reports the detection and characterization of two long-period transiting giant planets around the very young star HD 114082 (age ~15 Myr). The authors used photometry from TESS, CHEOPS, and ground-based surveys, as well as high-resolution spectroscopy, to determine the planets' periods, radii, and upper mass limits, overcoming the period-aliasing problem. They found nearly circular, coplanar orbits and low planet densities, indicating that the planets are 'puffy' at their young age.
Where its strength is
The strength of this work is that it opens a window into a previously inaccessible parameter space: young transiting giants with periods of hundreds of days. This allows direct tests of models of planet formation and early evolution, as well as the connection to the dusty disk.
Where it could go next
- It might be interesting to see how tidal interactions with the young star could have affected the orbits and internal structure of these planets. In our archive, there is an analysis of a system with an eccentric hot Jupiter where tidal forces play a key role in evolution.based on: Tidal Swings of an Eccentric Jupiter arXiv:2607.16406v1
- Another possible avenue is to investigate the dynamics of the dusty disk in this system and its connection to the planets. Nearby, there is a paper on dust rings at the edge of a distant system that may hint at how planets shape such structures.based on: Dust Rings at the Edge of a Distant System arXiv:2605.11486
- It would also be interesting to test the hypothesis that the planets migrated in the disk. The archive has a quick review of protoplanetary disk dynamics that covers accretion and migration.based on: How Dust Disks Dance Around Newborn Stars arXiv:2608.02204v1
Worth trying
- Estimate which tidal parameters (quality factor, damping time) are consistent with the observed orbits and ages of the planets.
- Model how planets with such masses and orbits could have formed the observed dusty disk (inner and outer belts).
- Test whether the planets could have acquired their orbits through migration in the protoplanetary disk, taking into account its evolution.
Nearby works in our archive
- Dust Rings at the Edge of a Distant Systemsimilarity 0.66
- Tidal Swings of an Eccentric Jupitersimilarity 0.64
- How Dust Disks Dance Around Newborn Starssimilarity 0.63
- How Tidal Waves Sort Planetssimilarity 0.62
- How a Swallowed Planet Spun Up a Starsimilarity 0.62
- Shadow or Mirage: Hunting a Moon Around a Scorching Jupitersimilarity 0.62
The closest work in the archive sits at 0.66 by meaning — the usual level for our corpus.
Original abstract
as written by the authors arXiv:2607.02685v1
We identify two large-radius planets around the F-type star HD 114082 as the longest-period young transiting exoplanets known. From the first transit, detected by NASA's Transiting Exoplanet Survey Satellite (TESS), and a second dip, spotted by the Next-Generation Transit Survey (NGTS), we predicted mid-transit times for HD 114082 b (planet b). We pinpoint its orbit (period Pb= 225.5504$$\pm$$0.0004 days) from a third transit captured with the ESA's CHaracterising ExOplanet Satellite and the upgraded Antarctic Search for Transiting ExoPlanets telescope (ASTEP+), alongside orbit-discriminating observations. Another dimming partly covered by ASTEP+ completes the four-transit series. We support with dynamical evidence the planetary nature of a deeper transit detected with TESS and NGTS, identifying planet c. Additionally, we reexamine the debris disk, fitting its excess emission with two dust components. Fundamental stellar parameters are inferred from stellar evolution models, while a joint modeling of photometric and radial-velocity time series yields the planetary parameters, with masses further constrained using an N-body code. For planet b, the semimajor axis a$$_b$$= 0.791$$\pm$$0.008 au, eccentricity eb$$\approx$$ 0, inclination ib= 89.791$$\pm$$0.014 degrees, radius Rb= 1.046$$\pm$$0.014 R$$_J$$, and 95 % confidence upper limit on its mass M$$_{95\%,b}$$= 1.6 M$$_J$$. For planet c, a$$_c$$= 0.99$$^{+0.03}_{-0.04}$$ au, ec$$\approx$$ 0, i$$_c$$= 89.701$$\pm$$0.011 degrees, R$$_c$$= 1.36$$\pm$$0.03 R$$_J$$, and M$$_{95\%,c}$$= 2.0 M$$_J$$ (0.24 M$$_J$$ if adding transit timing variation constrains). They seem to be moderate-to-low-mass giants in nearly resonant, coplanar, circular orbits that formed in situ, or beyond the snowline, and migrated inwards, shaping the disk.
Fun fact: The star HD 114082 lies in the Scorpius–Centaurus OB association — the same group of young stars as the HR 8799 system, where exoplanets were first directly imaged.
Key numbers
- Period of planet b: 225.5504 days
- Age of the star: 15 million years
- Radius of planet c: 1.36 R_J
- Mass of planet b (upper limit): 1.6 M_J
- Distance to the system: 95.06 pc