Exoplanets, -moons, -comets

The Epoch of Giant Planet Migration Planet Search Program. III. The Occurrence Rate of Young Giant Planets Inside the Water Ice Line

By Keith Cowing

Press Release

June 13, 2025

Filed under astornomy, exoplanet, giant planet, habitability

The Epoch of Giant Planet Migration Planet Search Program. III. The Occurrence Rate of Young Giant Planets Inside the Water Ice Line — The inferred occurrence rates of giant planets orbiting interior to the water ice line of Sun-like stars as a function of age. Schematic decreasing, consistent, and increasing giant planet frequency over time trends, resulting from different migration pathways, are also plotted as grey dashed, solid, and dotted lines, respectively. Our young measurement of 1.9 +2.6 −1.4% and the field-age measurement of 6.5 ± 0.7% from Johnson et al. (2010) are displayed in the blue and orange distributions, respectively. The shaded regions under each distribution show the 1σ, 2σ, and 3σ confidence intervals. If the occurrence rate of giant planets increases over time, then dynamical processes are the dominant migration pathway of giant planets. If the giant planet frequency is consistent between young and old systems, then giant planets likely arrived at their present-day locations through disk migration. A decreasing trend suggests that giant planets are efficiently engulfed by their host stars at early ages. — astro-ph.EP

We present statistical results from the Epoch of Giant Planet Migration RV planet search program.

This survey was designed to measure the occurrence rate of giant planets interior to the water ice line of young Sun-like stars, compare this to the prevalence of giant planets at older ages, and provide constraints on the timescale and dominant inward migration mechanism of giant planets.

Our final sample amounts to 85 single young (20-200 Myr) G and K dwarfs which we target across a 4-year time baseline with the near-infrared Habitable-zone Planet Finder spectrograph at McDonald Observatory’s Hobby-Eberly Telescope.

As part of this survey, we discovered the young hot Jupiter HS Psc b. We characterize survey detection completeness with realistic injection-recovery tests and measure an occurrence rate of 1.9+2.6−1.4% for intermediate-age giant planets (0.3<m_sini<13 M_Jup) within 2.5 AU. This is lower than the field age occurrence rate for the same planet masses and separations and favors an increase in the prevalence of giant planets over time from ∼100 Myr to several Gyr, although our results cannot rule out a constant rate.

A decaying planet occurrence rate is, however, strongly excluded. This suggests that giant planets located inside the water ice line originate from a combination of in situ formation or early migration coupled with longer-term inward scattering.

The completeness-corrected prevalence of young hot Jupiters in our sample is 1.5+2.2−1.1%–similar to the rate for field stars–and the 95% upper limit for young brown dwarfs within 5000 d is <3.6%.

Quang H. Tran, Brendan P. Bowler, William D. Cochran, Chad F. Bender, Samuel Halverson, Suvrath Mahadevan, Joe P. Ninan, Paul Robertson, Arpita Roy, Guðmundur Stefánsson, Ryan C. Terrien

Comments: 59 pages, 31 figures, 11 tables, accepted to AJ
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2506.08078 [astro-ph.EP] (or arXiv:2506.08078v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2506.08078
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Submission history
From: Quang Tran
[v1] Mon, 9 Jun 2025 18:00:00 UTC (1,958 KB)
https://arxiv.org/abs/2506.08078
Astrobiology,

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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