Exoplanetology: Exoplanets & Exomoons

Revised Mass and Orbit of Epsilon Eridani b: A 1 Jupiter-Mass Planet on a Near-Circular Orbit

By Keith Cowing

Status Report

astro-ph.EP

March 4, 2025

Filed under astro-ph.EP, epsilon Eridani, Epsilon Eridani b, exoplanet, Gaia DR2, Gaia DR3, Hipparcos, Hubble FGS, imaging

Revised Mass and Orbit of Epsilon Eridani b: A 1 Jupiter-Mass Planet on a Near-Circular Orbit — Comparison of the orbit posteriors incorporating different sources of data. The blue dots mark the location of the planet on 2025-01-01. The colors of the orbit draws match those in Figure 2 for easier cross-referencing. The bottom right panel shows the outer debris disk model fit to ALMA data by Booth et al. (2023). The ❉ indicates two models containing only RV data and only absolute astrometry data respectively, and whose posteriors are therefore completely independent. The models indicated by ✦ include RV data, but distinct sets of astrometric data, making the position angles they indicate on 2025-01-01 effectively independent. — astro-ph.EP

The mature Jovian planet ε Eridani b orbits one of the closest sun-like stars at a moderate separation of 3.5 AU, presenting one of the best opportunities to image a true analog to a solar system planet.

We perform a thorough joint reanalysis and cross-validation of all available archival radial velocity and astrometry data, combining data from eight radial velocity instruments and four astrometric sources (Hipparcos, Hubble FGS, Gaia DR2, and Gaia DR3).

We incorporate methodological advances that impact our findings including a principled treatment of correlation between Gaia DR2 and DR3 velocity and corrections for the changing light-travel time to this high proper motion system.

We revise the planet’s mass upward to 0.98±0.09M_jup and find that its orbit is nearly circular and close to coplanar with the outer debris disk. We further present one of the first models of an exoplanet orbit exclusively from absolute astrometry and independently confirm the planet’s orbital period.

We make specific predictions for the planet’s location at key imaging epochs from past and future observing campaigns. We discuss and resolve tensions between previous works regarding the eccentricity, inclination, and mass. Our results further support that ε Eridani b is one of the closest analogs to a Solar System planet yet detected around a nearby star.

William Thompson, Eric Nielsen, Jean-Baptiste Ruffio, Sarah Blunt, Christian Marois

Comments: Submitted to AJ. Comments welcome
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2502.20561 [astro-ph.EP] (or arXiv:2502.20561v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2502.20561
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Submission history
From: William Thompson
[v1] Thu, 27 Feb 2025 22:01:48 UTC (8,125 KB)
https://arxiv.org/abs/2502.20561
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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