In 5-6 biollion years the Sun will end its life as a white dwarf-star, just as most other main-sequence stars. But can a white dwarf support life?

A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored thermal energy. In January 2009, the Research Consortium on Nearby Stars project counted eight white dwarfs among the hundred nearest star systems of the Sun.
White dwarfs are thought to be the final evolutionary state of all stars whose mass is not high enough to become supernovae—over 97% of the stars in our galaxy.

To date the search for habitable Earth-like planets has primarily focused on nuclear burning stars. This research propose that this search should be expanded to cool white dwarf stars that have expended their nuclear fuel. The researcher. define the continuously habitable zone of white dwarfs, and show that it extends from ~0,005 - 0,02 AU for white dwarfs with masses from 0,4 - 0,9 solar masses, temperatures less than 10,000 K, and habitable durations of at least 3 billion years. As they are similar in size to Earth, white dwarfs may be completely eclipsed by terrestrial planets that orbit edge-on, which can easily be detected with ground-based telescopes. If planets can migrate inward or reform near white dwarfs,

The resaercher show that a global robotic telescope network could carry out a transit survey of nearby white dwarfs placing interesting constraints on the presence of habitable Earths. If planets were detected, He shows that the survey would favor detection of planets similar to Earth: similar size, temperature, rotation period, and host star temperatures similar to the Sun. The Large Synoptic Survey Telescope (LSST) could place even tighter constraints on the frequency of habitable Earths around white dwarfs. The confirmation and characterization of these planets might be carried out with large ground and space telescopes.

Source: arXiv.org