In a new study, University of California, Irvine astronomers describe how extraterrestrial life has the potential to exist on distant exoplanets inside a special area called the “terminator zone,” which is a ring on planets that have one side that always faces its star and one side that is always dark.
“These planets have a permanent day side and a permanent night side,” said Ana Lobo, a postdoctoral researcher in the UCI Department of Physics & Astronomy who led the new work, which was just published in The Astrophysical Journal. Lobo added that such planets are particularly common because they exist around stars that make up about 70 percent of the stars seen in the night sky – so-called M-dwarf stars, which are relatively dimmer than our sun.
The terminator is the dividing line between the day and night sides of the planet. Terminator zones could exist in that “just right” temperature zone between too hot and too cold.
“You want a planet that’s in the sweet spot of just the right temperature for having liquid water,” said Lobo, because liquid water, as far as scientists know, is an essential ingredient for life.
On the dark sides of terminator planets, perpetual night would yield plummeting temperatures that could cause any water to be frozen in ice. The side of the planet always facing its star could be too hot for water to remain in the open for long.