THE deep-frozen outer reaches of planetary systems may blossom with life as their stars enter old age.
As a Sun-like star exhausts its hydrogen fuel, its outer shells expand to form a red giant thousands of times brighter than the Sun. That means the “habitable zone” where life could exist will move outward, in our system to the region containing Pluto and the Kuiper Belt, Alan Stern of the Southwest Research Institute in Colorado told the Division for Planetary Sciences meeting last week.
That balmy stage lasts only up to 100 million years, but such distant objects could be “a…
