Exoplanets & Exomoons

GJ 357 d: Potentially Habitable World or Agent of Chaos?

By Keith Cowing
Status Report
October 4, 2023
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GJ 357 d: Potentially Habitable World or Agent of Chaos?
The architecture and HZ of the GJ 357 system, where the scale of the figure is 0.57 AU along each side. The CHZ is shown in light green, the OHZ extensions to the HZ are shown in dark green, and the orbits of the known planets are shown as solid circles. — astro-ph.EP

Multi-planet systems provide important laboratories for exploring dynamical interactions within the range of known exoplanetary system architectures.

One such system is GJ 357, consisting of a low-mass host star and three orbiting planets, the outermost (planet d) of which does not transit but lies within the Habitable Zone (HZ) of the host star. The minimum mass of planet d causes its nature to be unknown, both in terms of whether it is truly terrestrial and if it is a candidate for harboring surface liquid water.

Here, we use three sectors of photometry from the Transiting Exoplanet Survey Satellite (TESS) to show that planets c and d do not transit the host star, and therefore may have masses higher than the derived minimum masses. We present the results for a suite of dynamical simulations that inject an Earth-mass planet within the HZ of the system for three different orbital and mass configurations of planet d.

These results show that planet d, rather than being a potentially habitable planet, is likely a source of significant orbital instability for other potential terrestrial planets within the HZ. We find that relatively small eccentricities of planet d cause a majority of the HZ to be unstable for an Earth-mass planet. These results highlight the importance of dynamical stability for systems that are prioritized in the context of planetary habitability.

Stephen R. Kane, Tara Fetherolf

Comments: 10 pages, 4 figures, accepted for publication in the Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2310.02327 [astro-ph.EP] (or arXiv:2310.02327v1 [astro-ph.EP] for this version)
Submission history
From: Stephen Kane
[v1] Tue, 3 Oct 2023 18:02:55 UTC (568 KB)

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) 🖖🏻