A Terrestrial Exoplanet in a One AU Orbit in a Binary Star System Separated by 15 AU

A Terrestrial Planet in a ~1 AU Orbit Around One Member of a ~15 AU Binary

Authors:

Gould et al

Abstract:

We detect a cold, terrestrial planet in a binary-star system using gravitational microlensing. The planet has low mass (2 Earth masses) and lies projected at a⊥,ph ~ 0.8 astronomical units (AU) from its host star, similar to the Earth-Sun distance. However, the planet temperature is much lower, T less than 60 Kelvin, because the host star is only 0.10--0.15 solar masses and therefore more than 400 times less luminous than the Sun. The host is itself orbiting a slightly more massive companion with projected separation a⊥,ch=10--15 AU. Straightforward modification of current microlensing search strategies could increase their sensitivity to planets in binary systems. With more detections, such binary-star/planetary systems could place constraints on models of planet formation and evolution. This detection is consistent with such systems being very common.