Transit surveys for Earths in the habitable zones of white dwarfs

Understand

To date the search for habitable Earth-like planets has primarily focused on nuclear burning stars.

• I propose that this search should be expanded to cool white dwarf stars that have expended their nuclear fuel.
• I define the continuously habitable zone of white dwarfs, and show that it extends from ~0.005 to 0.02 AU for white dwarfs with masses from 0.4 to 0.9 solar masses, temperatures less than 10,000 K, and habitable durations of at least 3 Gyr.
• As they are similar in size to Earth, white dwarfs may be deeply eclipsed by terrestrial planets that orbit edge-on, which can easily be detected with ground-based telescopes.