Dynamical Packing In The Habitable Zone: The Case Of Beta CVn

Calculated V-band magnitude of an Earth analog in the HZ of the nearest stars, as a function of the fraction of the HZ for those stars that are within instrument detection limits, scaled by the Hill radius. The color of the stars indicates their effective temperature (spectral type) and labels are provided for well-known nearby stars, including Beta CVn.

Uncovering the occurrence rate of terrestrial planets within the Habitable Zone (HZ) of their host stars has been a particular focus of exoplanetary science in recent years.

The statistics of these occurrence rates have largely been derived from transiting planet discoveries, and have uncovered numerous HZ planets in compact systems around M dwarf host stars. Here we explore the width of the HZ as a function of spectral type, and the dynamical constraints on the number of stable orbits within the HZ for a given star. We show that, although the Hill radius for a given planetary mass increases with larger semi-major axis, the width of the HZ for earlier-type stars allows for more terrestrial planets in the HZ than late-type stars.

In general, dynamical constraints allow ∼6 HZ Earth-mass planets for stellar masses ≳0.7M⊙, depending on the presence of farther out giant planets. As an example, we consider the case of Beta CVn, a nearby bright solar-type star. We present 20 years of radial velocities (RV) from the Keck/HIRES and APF instruments and conduct an injection-recovery analysis of planetary signatures in the data. Our analysis of these RV data rule out planets more massive than Saturn within 10~AU of the star. These system properties are used to calculate the potential dynamical packing of terrestrial planets in the HZ and show that such nearby stellar targets could be particularly lucrative for HZ planet detection by direct imaging exoplanet missions.

Stephen R. Kane, Margaret C. Turnbull, Benjamin J. Fulton, Lee J. Rosenthal, Andrew W. Howard, Howard Isaacson, Geoffrey W. Marcy, Lauren M. Weiss

Comments: 10 pages, 6 figures, 2 tables, accepted for publication in the Astronomical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:2006.13962 [astro-ph.EP] (or arXiv:2006.13962v2 [astro-ph.EP] for this version)
Submission history
From: Stephen Kane
[v1] Wed, 24 Jun 2020 18:01:16 UTC (2,574 KB)
[v2] Fri, 26 Jun 2020 05:28:41 UTC (2,574 KB)

Please follow Astrobiology on Twitter.

  • submit to reddit