On life around white dwarfs, and on brown dwarfs

Sol + white dwarf for comparison.

Two interesting links to share today that pertain to the likely frequency of life elsewhere in the universe - this article on why planets around white dwarfs may be one of the best places to search for life, and this one on the possibility of life on brown dwarfs. While I recommend reading both, the former is more interesting to think about as it also involves a proposition to survey white dwarfs for potentially habitable planets. The reasons for this are simple:

- While white dwarfs are only created after a sun about the size of ours turns into a red giant, after its red giant phase is over it turns into a remarkably stable star for the next few billion years

- Planets could easily form during this red giant - white dwarf period

- The habitability zone of a white dwarf is extremely close, a mere 1 to 3 million km or so from the star (Earth for comparison is 150 million km away). Thanks to this, the planets around white dwarfs that we want to find would be easily detectable in just a few days. Such a survey would then be easy: watch a white dwarf for just a bit over a day, and if there is no dimming during this period, then that means that either 1) there is no planet in the white dwarf's habitable zone, or 2) there is a planet but we can't see it because its orbit doesn't bring it in between us and its host star. In either case you then turn to the next star and check it out for a bit over a day too.