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LZ地下这篇文章和原文有相似性吗?
Red dwarfs, also known as M stars, are roughly one-fifth as massive as the Sun and up to 50
times fainter.when a planet orbits very near a star, the star’s gravitational pull can force the world
to become “tidally locked” to it. When a planet is tidally locked to its star, it will always show the
same side to its star, just as the Moon always shows the same side to Earth. This causes the
planet to have one permanent day side and one permanent night side.
The extremes of heat and cold that tidally locked planets experience could make them
profoundly different from Earth. For example, prior research speculated the dark sides of
tidally locked planets would become so cold that any water there would freeze. Sunlight would
make water on the sunlit side evaporate, and this water vapor could get carried by air currents
to the night sides, eventually leading to sheets of ice miles thick on the night sides and
removing all water from the sunlit sides. Life as we know it probably could not develop on the
day sides of such planets. Although they would have sunlight for photosynthesis, they would
have no water to serve as the primordial soup for life to swim in.
To see how habitable tidally-locked planets really are, scientists devised a 3D global climate
model of planets that simulated interactions between the atmosphere, ocean, sea ice, and
land, as well as a 3-D model of ice sheets large enough to cover entire continents.
The researchers modeled three different arrangements of continents for all these planets. One
was a water world with no continents and global oceans of varying depths. Another involved a
supercontinent covering the night side and an ocean covering the day side. The last mimicked
Earth’s configuration of continents. The planets also had atmospheres similar to Earth’s, but
the researchers also tested lower levels of the greenhouse gas, carbon dioxide, which traps
heat and helps keep planets warm.
The important implication is that it may be easier than previously thought to keep liquid water
on the dayside of a tidally locked planet, where photosynthesis is possible,” Abbot said.
“There are many issues that will affect the habitability of M-star planets, but our results suggest
at least that water-trapping on the night side will only be a problem for relatively dry planets
with large continents on their nightside and relatively low geothermal heat flux.” |
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