According to new research in The Astrophysical Journal, the terminator planets could be a good spot for hosting extra-terrestrial life.
Key points
- On Earth, the terminator moves around over the course of a day, but on some planets it’s fixed in place: called “tidally locked” planets, the same side always faces its star.
- The tidal locking occurs when the gravitational interaction between two bodies “locks” the smaller body’s rotation to the same period as its orbit, so that one side is always facing the larger body.
- It particularly occurs in exoplanets with close orbits, because the gravity of the star stretches the exoplanet in such a way that the distortion applies a braking effect.
- Tidally locked planets have a half where it’s always day, a half where it’s always night, and a “terminator zone” where it’s always twilight.
- We see this with Earth and the Moon, too. These planets have a permanent day side and a permanent night side, akin to how the moon, from the vantage of earth, always shows the same side despite its rotations and revolutions.
- The ‘terminator’ is the dividing line between the ‘day’ and ‘night’ sides of the planet and terminator zones are the regions that could exist in that sweet spot between too hot and too cold.
- Such planets are quite 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 dark sides of terminator planets, would mean a perpetual night and freezing temperatures, whereas the side facing the star could be too hot for water to remain liquid.
- According to the study, astronomers have been able to show that terminator planets can sustain habitable climates confined to this terminator region because researchers have mostly studied ocean-covered exoplanets in their search for candidates for habitability.
