Future Earth. Artwork of the surface of a barren future Earth orbiting the Sun (blue, lower left), which has become a white dwarf. The Moon is seen at centre right. Eventually our Sun will exhaust its nuclear fuel supply and undergo gravitational collapse. It will then be known as a white dwarf. At this stage in its evolution it will be very small and faint. Because it will no longer have an internal energy supply, it will supply no heat to Earth, which will become too cold to sustain any life. It is thought that our Sun will become a white dwarf in around 5 billion years time.