This image may not be used by or to promote the arms, nuclear power or tobacco industries or any religious organisation, or in any discriminatory way, or to imply the endorsement by ESO of any product, service or activity Illustration showing Proxima d (right), an exoplanet candidate orbiting the red star Proxima Centauri (orange, left), the closest star to the Solar System. Proxima d has a mass a quarter of the Earth and is one of the lightest and exoplanets to be discovered. Exoplanets Proxima c and Proxima d, which also orbit Proxima Centauri, are also shown.