# If Kepler-444 planets existed for 11.2 billion years, why fear for life on Earth after six billion years?

According to recent news, Kepler-444, a 11.2 billion year old star, has a system of five planets. It has a mass of 3/4 of solar mass. So I believe both Kepler 444 and the Sun will share the fate of 'orange main sequence stars'. If so, while scientists fear for life on Earth in the coming billion years, which is only one sixth for our solar system lifetime, how is it that the Kepler-444 planets have existed for a longer period of time?

• Scientists don't fear for the Earth. They fear for the life on it, specifically for the human variety. High surface temperatures will render the Earth uninhabitable in a billion years or so, but the planet itself will be just fine for a while after that. – David H Feb 7 '15 at 8:14

The rate of evolution of main sequence stars is highly dependent on their mass. Roughly speaking, the time on the main sequence is proportional to $M^{-5/2}$, where $M$ is the mass of the star. Thus if Kepler 444 has $M=0.75\ M_{\odot}$, it can live for $0.75^{-5/2} = 2.05$ times as long as the Sun on the main sequence.