Exoplanets, -moons, -comets

The HD 60779 Planetary System: A Transiting Sub-Neptune On A 30-day Orbit And A More Massive Outer World

By Keith Cowing
Press Release
August 28, 2025
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The HD 60779 Planetary System: A Transiting Sub-Neptune On A 30-day Orbit And A More Massive Outer World
Transit light curves and fits for HD 60779 b. The transit models were all fit simultaneously with the RVs, details listed in Table 2. The upper left panel shows the flattened 120 s cadence data from TESS Sector 34. This is the original transit detection. The lower left panel shows the flattened 20 s cadence data from TESS Sector 88. The upper right panel shows the CHEOPS light curve, with the detrending model plotted. The lower right panel shows the detrended CHEOPS transit light curve, fit with the transit model. In all panels, the black points show the data in bins of 0.025 d. — astro-ph.EP

We present the discovery of the planetary system orbiting the bright (V = 7.2), nearby (35 pc), Sun-like star HD 60779, which has a mass of 1.050 +/- 0.044 solar masses and a radius of 1.129 +/- 0.013 solar radii.

We report two TESS transits and a subsequent CHEOPS transit of HD 60779 b, a sub-Neptune with a radius of 3.250 (+0.100 / -0.098) Earth radii on a 29.986175 (+0.000030 / -0.000033) day orbit. Additionally, 286 HARPS-N radial velocity measurements reveal the mass of planet b (14.7 +1.1 / -1.0 Earth masses) and the presence of an outer planet, HD 60779 c, with an orbital period of 104.25 (+0.30 / -0.29) days and a minimum mass (m sin i) of 27.7 +/- 1.6 Earth masses.

Both planets’ orbits are consistent with being circular, suggesting that they have a dynamically quiet history. The data are not sufficient to determine whether planet c transits. HD 60779’s uniquely high systemic radial velocity (129.75 +/- 0.12 km/s) allows its Lyman-alpha emission to avoid absorption by the interstellar medium, making it a prime candidate for probing atmospheric escape from HD 60779 b.

HD 60779 is also the third-brightest host of a sub-Neptune with orbital period greater than 25 days and with both mass and radius measured, distinguishing it in terms of accessibility to spectroscopic characterization.

Victoria DiTomasso, David Charbonneau, Andrew Vanderburg, Mercedes López-Morales, Shreyas Vissapragada, Annelies Mortier, Thomas G. Wilson, Elyse Incha, Andrew Collier Cameron, Luca Malavolta, Lars A. Buchhave, David W. Latham, Matteo Pinamonti, Stephanie Striegel, Michael Fausnaugh, Luke Bouma, Ben Falk, Robert Aloisi, Xavier Dumusque, A. Anna John, Ben S. Lakeland, A. F. Martínez Fiorenzano, Luca Naponiello, Belinda Nicholson, Emily K. Pass, Francesco Alfonso Pepe, Federica Rescigno, Alessandro Sozzetti, Daisy A. Turner, Saul A. Rappaport, Mark Omohundro, Brian P. Powell, Robert Gagliano, Thomas L. Jacobs, Veselin B. Kostov, Martti H. Kristiansen, Daryll M. LaCourse, Allan R. Schmitt, Hans Martin Schwengeler, Ivan A. Terentev

Comments: 18 pages, 12 figures, submitted to AAS Journals
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2508.16805 [astro-ph.EP] (or arXiv:2508.16805v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2508.16805
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Submission history
From: Victoria DiTomasso
[v1] Fri, 22 Aug 2025 21:16:24 UTC (4,928 KB)
https://arxiv.org/abs/2508.16805
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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