Expert: Courtney Seligman - 1/13/2010

Question
Hello Courtney.  I was wondering if a white dwarf star was theoretically capable of supporting a living planet such as the Earth given its low luminosity and high density.  I have searched the Internet using the different search engines but all I keep coming up with are "just the facts" answers without any theoretical input.  Your help in this matter would be so greatly appreciated.

Answer
The density of the star wouldn't make any difference -- just the size of the planet's orbit, and the luminosity of the star.

Typical white dwarfs are about ten thousand times fainter than the Sun. This means that to have the same temperature as the Earth, the orbit of the planet would have to be a hundred times smaller than that of the Earth, or about 900,000 miles from the white dwarf.

This distance would be very close to the surface of a normal star, and well inside the red giant the star would become before collapsing to become a white dwarf, so no planet could form at such a distance, and survive the events prior to the white dwarf stage. But if you could somehow move a planet from a larger orbit to a smaller one, the idea might work. In fact, I would be surprised if it hasn't been used in some science fiction story or other (for instance, although I haven't read "2010", the movie's ending only makes sense if Jupiter is artificially transformed into a white dwarf).

(MINOR NOTE: Thank you for the kind comments, and your plan to acknowledge my input in your novel; but if you do so, you should be aware than I am a "him", not a "her".)