Searching For Earths

Astronomers searching for Earth-like exoplanets have tended to concentrate on looking around Sun-like stars. That's reasonable enough, but a group of researchers has recently added a time factor to that approach. To date, the search has focused on stars that are currently Sun-like, but we are confident, this group points out, that such stars end their lives as white dwarfs-- a class of star extremely common in the galaxy. The researchers argue, therefore, that white dwarfs should be studied to determine how many of their spectra contain elements heavier than helium. Those dwarfs that have heavier elements may also have planetary systems, possibly including rocky worlds like Earth.

A problem with that approach may be how stars get to be white dwarfs. The Sun, for example, will theoretically bloat into a red giant before collapsing into a white dwarf. During the red giant phase, Mercury, Venus, and possibly Earth will be destroyed. True, during that phase, the "life belt" around the Sun may make worlds like Mars and Saturn's Titan more hospitable to life, but that would not hold after the Sun becomes a tiny white dwarf.