At the moment, the only model we have for the habitability of planets is Earth. There may be life on other planets in the large, open galaxy, but we can be sure it only arose in ours.
The problem is that nothing we've discovered so far is exactly like our planet in size, composition, position within the planetary system, and proximity to its star - the ideal "Goldilocks" distance for temperatures favorable for life as we know it.
In fact, most of the 5.300 planets we've discovered so far are significantly closer to their host stars, compared to Earth's distance from the Sun. Not only are they sizzling, but they're also tidally locked as a result of their proximity. This indicates that one side is constantly cooking under the endless sunlight while facing the star, while the other side is always facing away while freezing in perpetual darkness.
Close-orbiting binary exoplanets may be habitable in a thin bending region known as the terminator, where day and night meet, according to a recent paper.
Geophysicist Ana Lobo of the University of California at Irvine believes you want a planet in the ideal range to have liquid water.
“On this planet, the day side can be extremely hot and uninhabitable, while the night side can be icy cold and perhaps even icy. There may be large glaciers on the night side.”
The current state of our technology significantly hinders our search for Earth-like exoplanets. Finding planets that orbit their stars very tightly in less than 100 days is where our most effective strategies excel.
If we only considered Sun-like stars, this would be problematic in terms of possible habitability. But the vast majority of stars in the galaxy are red dwarfs, and they are smaller, dimmer and much cooler than our star.
This brings the habitable zone much closer, but it also creates the problem of tidal locking. When two objects gravitationally interact, the rotation of the smaller object is "locked" to its orbital period, causing one side to always face the larger object. The gravitational pull of the star stretches the exoplanet so much that this distortion creates a braking effect, especially in close-orbiting exoplanets. Earth and Moon both exhibit this.
Also called "eyeball planets," exoplanets have harsh climates on both the day and night sides, which may not be very friendly. Lobo and colleagues used specialized climate modeling software often used for Earth to examine whether such worlds are likely to be habitable.
Because life on Earth depends on water, previous research into the potential habitability of exoplanets has placed much greater emphasis on water-rich worlds. The team's goal was to expand the universe where we needed to look for evidence of extraterrestrial life.
Although they don't have large oceans, some water-limited planets may still contain lakes or other small bodies of liquid water, and these conditions can actually be quite promising, according to Lobo.
However, the team's research suggested that the additional water would likely make the ocular planets less habitable. Interaction with the star would fill the atmosphere with steam that could cover the entire globe and would produce suffocating greenhouse effects if such a world had liquid seas on the day side.
But if there is too much land on the outer planet, the terminator becomes more habitable. There, as temperatures rise beyond freezing, ice from night-side glaciers can melt and turn the terminator into a habitable ring surrounding the exoplanet.
This is consistent with research published in the journal Astrobiology in 2013. Collectively, they suggest that it may be useful to consider exoplanets when conducting future research into the possibility of life on extrasolar worlds.
According to Lobo, “by investigating these exotic climatic states in the near future, we can increase our chances of discovering and accurately identifying a habitable planet.
source: sciencealert
Günceleme: 17/03/2023 14:54