Unbelievable! ALIENS could be hiding in 'terminator zones' on distant exoplanets

Scientists speculate that aliens may be hiding in special "terminator zones" on far-off worlds where the temperature is just right. Exoplanets are planets that exist outside of our solar system, and many of them are tidally locked, which means that one side faces the star they circle and the other is always in the dark.

University of California, Irvine astronomers have discovered that these planets have a band surrounding them that may be able to hold liquid water, a necessary component for life.

It is known as the "terminator zone" because it marks the boundary between the exoplanet's day and night sides. Any water obtained would presumably be solidly frozen on the chilly night side but evaporate on the sunny dayside.

According to lead author Dr Ana Lobo, "The dayside can be scorching hot, well beyond habitability, and the night side is going to be freezing, potentially covered in ice."

"You could have large glaciers on the night side. You want a planet that's in the sweet spot of just the right temperature for having liquid water," Dr Lobo added.

Gravity is a property of all objects having mass, and the more massive an object is, the stronger its gravitational attraction.

In the case of a planet orbiting a star, the star's gravitational force pushes the planet towards it, while its own gravity also pulls it towards the star.

The interaction of these forces, as well as the speed and direction of the planet's motion before locking into orbit, determine a planet's orbital path.

A planet's shape may be distorted if it orbits a star very closely, causing the planet to bulge on one side.

This bulge experiences a higher gravitational pull than other parts of the globe, which causes the planet's axial rotation to slow down.

This eventually slows to the point that just the bulging side faces the star and rotation ceases altogether, leading it to become tidally locked.

Tidally locked exoplanets are more likely to be found near 'M-dwarf' stars, a subclass of the red dwarf cooler and smaller than the Sun.

This is because smaller exoplanets, which are more vulnerable to tidal forces than larger ones, are more likely to be caught in the orbit of smaller stars.

As M-dwarf stars make up about 70 per cent of the stars seen in the night sky, tidally locked exoplanets are considered relatively common.

For their study, published in The Astrophysical Journal, the researchers wanted to find out whether these planets have life-sustaining conditions, like the ability to hold water in its liquid form.

If so, this would significantly increase the pool of planets astronomers could study for extraterrestrial life.

The researchers simulated the climate of several tidally locked exoplanets, looking at their varying temperatures, wind patterns and radiation exposure.

They employed software often used to simulate the climate of Earth while slowing the planet's rotation.

Research revealed a "just right" zone around these planets' terminator that could support liquid water and life development.

This was only true when the planet had a lot of land; if it were mostly covered in the ocean, the water on the dayside would evaporate and blanket the entire world in vapour.

The terminator zone's temperature would shift, rendering it uninhabitable.

"Ana has shown if there's a lot of land on the planet, the scenario we call 'terminator habitability' can exist a lot more easily," co-author Dr Aomawa Shields noted.

"These new and exotic habitability states our team is uncovering are no longer the stuff of science fiction – Ana has done the work to show that such states can be climatically stable."

Most research on the possibility of life has focused on planets with abundant water.

Dr Lobo said, "We are trying to draw attention to more water-limited planets, which despite not having widespread oceans, could have lakes or other smaller bodies of liquid water, and these climates could actually be very promising."

The researchers assert that they believe this is the first instance in which astronomers have demonstrated that there may be a chance for life in an exoplanet's terminator zone.

Their discovery might suggest that researchers searching for indications of life on exoplanets need to be mindful that they might be concealed in some regions.

Also, it has broadened the range of planets that can be explored to include those that do not have a significant water surface.

"By exploring these exotic climate states, we increase our chances of finding and properly identifying a habitable planet in the near future," Dr Lobo concluded.