In a new study, astronomers at the University of California, Irvine, explain that extraterrestrial life has the potential to exist on distant exoplanets in a special region called the “terminator zone,” a ring on planets that always faces the star and is a ring on planets. one side always looks at the star. darkness

“These planets have a persistent day side and a permanent night side,” said Ana Lobo, a postdoctoral researcher in the UCI Department of Physics and Astronomy, who led the new study, just published in The Astrophysical. Daily. Lobo added that such planets are particularly common because they exist around stars that make up about 70 percent of the stars visible in the night sky – so-called M-dwarf stars, which are relatively fainter than our Sun.

The Terminator is the line that separates the day and night sides of the planet. Terminator zones can be located in the “just right” temperature zone between very hot and very cold.

“You need a planet with an optimal temperature for liquid water,” Lobo said, because scientists know that liquid water is an essential ingredient for life.

Persistent night on the dark sides of Terminator planets causes temperatures to drop significantly, which can cause water to freeze to ice. The side of the planet that always faces the star may be too hot for the water to be exposed for extended periods of time.

“This is a planet where the day side could be far from habitable, very hot, and the night side could freeze, potentially covered in ice. There could be big glaciers on the night side,” Lobo said.

Lobo, along with UCI associate professor of physics and astronomy Aomawa Shields, modeled the climates of the terminator planets using software commonly used to model our planet’s climate, but made some adjustments, including slowing the planets’ rotations.

This is believed to be the first time astronomers have demonstrated that such planets can support habitable climates confined to this terminator region. Historically, researchers have mostly studied ocean-covered exoplanets in search of habitability candidates. But now that Lobo and her team have shown that terminator planets are also viable harbors for life, it expands the options for life-seeking astronomers.

“We’re trying to draw attention to planets with more water that may have lakes or other small bodies of water despite not having oceans, and such climates can be very promising,” Lobo said.

Lobo added that one of the keys to the discovery was to determine exactly which planet in the terminating region could hold liquid water. If the planet was mostly covered with water, the star-facing water the team found would most likely evaporate, covering the entire planet with a thick layer of vapor.

But if there is land, this effect should not exist.

“Ana showed that if there’s a lot of land on a planet, then the scenario we call ‘The Habitable Terminator’ can exist much more easily,” Shields said. Said. “These new and exotic habitats our team has discovered are no longer science fiction. Ana did what it takes to show that such conditions can be climatically stable.”

Recognizing that terminator zones are potential havens for life also means that astronomers will need to adjust the way they study exoplanet climates for signs of life, as biosignatures created by life can only be present in certain parts of a planet’s atmosphere.

The study will also help inform future efforts by teams using telescopes such as the James Webb Space Telescope or the Large Ultraviolet Optical Infrared Telescope, currently under development at NASA, to search for planets that may harbor extraterrestrial life.

“By exploring these exotic climates, we increase our chances of finding and accurately identifying a habitable planet in the near future,” Lobo said. Said.