Super-Earth GJ 667Cc: Age and XUV Irradiances of the Temperate-zone Planet with Potential for Advanced Life

Abstract

Abstract GJ 667Cc is a nearby (23.6 lt-yr) super-Earth that orbits within the habitable zone (HZ) of its ∼M2V host star and has Earth-like properties: (M- sin ( i ) ∼ 4.1 M ⊕ ; R ∼ 1.7 R ⊕; T eq (A = 0.3) ∼ 277 K). The age of the star/planet is poorly constrained at 2 ≳ Gyr. Age is crucial in evaluating the potential for complex life. We determine an age of ∼6.10 ± 2.2 Gyr from our recent Age-Rotation relations. This is compatible with its low metallicity ([Fe/H] ∼ −0.59 ± 0.1 dex), weak coronal/chromospheric X-ray/FUV emissions, and space motions. We also determine the photodissociating/photoionizing X-ray-UV irradiances from Chandra and ROSAT X-ray and HST/FUV observations. Like most HZ-planets hosted by M-dwarfs, these irradiances are much higher than Earth's and are detrimental to the planet's atmosphere retention, water inventories, and habitability. A strong geomagnetic field could mitigate atmospheric erosion, permitting life to develop.