Lava planets are a class of rocky exoplanets that orbit so close to their star that their surface parts are fused. Indeed, daytime temperatures can be high enough to maintain a rock vapor atmosphere detectable through transit and eclipse spectroscopy as well as phase curves.
According to scientists at McGill University, York University and the Indian Institute of Science Education, the atmosphere and weather cycle of at least one of these exoplanets are even stranger, with evaporation and precipitation of rocks, supersonic winds that they rage over 5000 km / h. and a 100 km deep magma ocean.
One planet is K2-141b, an Earth-sized exoplanet with a surface, ocean and atmosphere all made up of the same ingredients: rocks. Using computer simulations, the scientists predicted conditions on K2-141b. The extreme weather predicted by their analysis could permanently change K2-141b’s surface and atmosphere over time.
In investigating the exoplanet’s illumination pattern, the team found that about two-thirds of K2-141b is exposed to perpetual daylight, unlike the illuminated hemisphere we’re used to on Earth. Since K2-141b belongs to a subset of rocky planets that orbit very close to their star, this proximity keeps the exoplanet gravitationally locked in place.
Nicolas Cowan, professor in the Department of Earth and Planet Sciences at McGill University, said: “The night side experiences freezing temperatures below -200 C. At an estimated temperature of 3000 C, the day side of the exoplanet is hot enough not only to melt the rocks but also to vaporize them, eventually creating a subtle atmosphere in some areas. Our discovery probably means that the atmosphere extends a little beyond the magma ocean shore, making it easier to spot with space telescopes. “
The rock vapor atmosphere created by the extreme heat experiences precipitation. Just like the water cycle on Earth, where water evaporates, rises into the atmosphere, condenses, and falls back as rain, so do the sodium, silicon monoxide and silicon dioxide on K2-141b. The mineral vapor formed by the evaporated rock is swept to the freezing side of the night by the supersonic winds and the rocks “rain” again in an ocean of magma. The resulting currents ebb towards the warm side of the exoplanet, where the rock evaporates once again.
Scientists noted, “The next step will be to check if these predictions are correct. We now have data from the Spitzer Space Telescope which should give them a first glimpse of the exoplanet’s day and night temperatures. “
With the launch of the James Webb Space Telescope in 2021, they will also check whether the atmosphere behaves as expected.
- T. Giang Nguyen et al. Modeling of the atmosphere of the lava planet K2-141b: implications for low and high resolution spectroscopy. DOI: 10.1093 / mnras / staa2487