Living with a red giant
Stories from Physics for 11-14 14-16
It has been suggested that once a main sequence star transitions into a red giant, life might develop in the habitable zone of the newly formed giant star. For a star of the mass of the Sun, the habitable zone may move out to between 2 - 9 astronomical units (one astronomical unit is approximately the distance from the Earth to the Sun) during the first stage of evolution after leaving the main sequence and then up to as far as 22 astronomical units from the star after the core helium flash. It has been predicted that Titan, the largest moon of Saturn, may become a habitable planet following the transition of the Sun into a red giant.