Among the most extreme planets discovered beyond the edges of our solar system are the lava planets: hot, fiery worlds that spin so close to their host star that some areas are likely oceans of molten lava.
Scientists at McGill University, York University and the Indian Institute of Science Education say the atmosphere and weather cycle of at least one of these exoplanets is even stranger, with evaporation and precipitation of rocks, supersonic winds raging at more than 5000 km / h. , and an ocean of magma 100 km deep.
In a study published in Monthly notices from the Royal Astronomical Society, scientists use computer simulations to predict conditions on K2-141b, an Earth-sized exoplanet with a surface, an ocean, and an atmosphere all made of the same ingredients: rocks. The extreme weather conditions predicted by their analysis could permanently alter the surface and atmosphere of K2-141b over time.
“The study is the first to make predictions of weather conditions on K2-141b that can be detected hundreds of light years away with next-generation telescopes such as the James Webb Space Telescope,” says author Principal Giang Nguyen, a doctoral student at York University who worked under the supervision of Professor Nicolas Cowan of McGill University on the study.
Two-thirds of the exoplanet face endless daylight
By analyzing the exoplanet’s lighting pattern, the team found that about two-thirds of K2-141b faces perpetual daylight – rather than the lighted hemisphere we’re used to on Earth. K2-141b belongs to a subset of rocky planets that orbit very close to their star. This proximity keeps the gravitationally locked exoplanet in place, meaning that the same side always faces the star.
The night side experiences freezing temperatures below -200 C. The day side of the exoplanet, at around 3000 C, is hot enough to not only melt the rocks but also vaporize them, ultimately creating a thin atmosphere in some areas. . “Our discovery probably means that the atmosphere extends a little beyond the shore of the magma ocean, which makes it easier to spot with space telescopes,” explains Nicolas Cowan, professor in the Department of Earth and Earth Sciences. planets at McGill University.
Like the Earth’s water cycle, only with rocks
Remarkably, the rock vapor atmosphere created by the extreme heat experiences precipitation. Just like the water cycle on Earth, where water evaporates, rises in the atmosphere, condenses, and falls back as rain, so do sodium, silicon monoxide, and dioxide. of silicon on K2-141b. On Earth, rain returns to the oceans, where it will evaporate again and the water cycle repeats. On K2-141b, the mineral vapor formed by the evaporated rock is swept to the icy night side by supersonic winds and the rocks “rain” down into an ocean of magma. The resulting currents flow back to the warm side of the exoplanet, where the rock evaporates again.
Still, the cycle on K2-141b is not as stable as that on Earth, scientists say. The return flow of the magma ocean to the day side is slow, and therefore they predict that the mineral composition will change over time – ultimately altering the very surface and atmosphere of K2-141b.
“All rocky planets, including Earth, started out as molten worlds, but then quickly cooled and solidified. Lava planets give us rare insight at this stage in planetary evolution, ”says Professor Cowan of the Department of Earth and Planetary Sciences.
The next step will be to test whether these predictions are correct, say the scientists. The team now has data from the Spitzer Space Telescope that should give them a first glimpse of the day and night temperatures of the exoplanet. With the launch of the James Webb Space Telescope in 2021, they will also be able to check whether the atmosphere is behaving as expected.
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