The 55 Cancri System: Fundamental Stellar Parameters, Habitable Zone Planet, and Super-Earth Diameter

TL;DR

This study precisely measures the stellar parameters of 55 Cancri, assesses the habitable zone of its planets, and determines the super-Earth's diameter and density, providing insights into its potential habitability.

Contribution

It provides the first direct measurement of 55 Cancri's stellar radius and refines the physical characteristics of its transiting super-Earth, enhancing understanding of its habitability.

Findings

55 Cancri's stellar radius is 0.943 R_sun.

Planet 55 Cnc f spends most of its orbit in the habitable zone.

Super-Earth 55 Cnc e has a diameter of approximately 2.1 Earth radii.

Abstract

The bright star 55 Cancri is known to host five planets, including a transiting super-Earth. We use the CHARA Array to directly determine the following of 55 Cnc's stellar astrophysical parameters: $R=0.943 \pm 0.010 R_{\odot}$, $T_{\rm EFF} = 5196 \pm 24$ K. Planet 55 Cnc f ($M \sin i = 0.155 M_{Jupiter}$) spends the majority of the duration of its elliptical orbit in the circumstellar habitable zone (0.67--1.32 AU) where, with moderate greenhouse heating, it could harbor liquid water. Our determination of 55 Cancri's stellar radius allows for a model-independent calculation of the physical diameter of the transiting super-Earth 55 Cnc e ($\simeq 2.1 R_{\earth}$), which, depending on the assumed literature value of planetary mass, implies a bulk density of 0.76 $\rho_{\earth}$ or 1.07 $\rho_{\earth}$.