The James Webb space telescope has discovered new data that could indicate how the WASP-121B exoplanet formed and how the gas and dust disc surrounded its star. The key is in molecules found in its atmosphere: methane and silicon monoxide.
This is the main conclusion of two international studies led by astronomers from the HEIDELBERG Max Planck Institute (Mppia), Thomas Evans-Soma and Cyril Gapp, whose details have been published on Monday in the magazines Nature Astronomy and The Astronomical Journal.
During the observations, the equipment found multiple key molecules: water vapor, carbon monoxide and silicon monoxide, and with these data they made an inventory of carbon, oxygen and silicon in the exoplanet.
Wastp-121b is an ultra hot giant planet that orbits very close to its host star and completes an orbit in approximately 30.5 hours.
The planet also has two different hemispheres: one that is always oriented towards the host star, with temperatures that exceed 3000ºC, and an eternal night side where temperatures fall to 1500ºC.
The team investigated the abundance of compounds that evaporate at very different temperatures, which provided clues about the formation and evolution of the planet.
The team concluded that Wasp-121B probably accumulated most of its gas in a cold enough region so that the water remained frozen, but warm enough for methane (CH4) to evaporate and existed in a gaseous form.
Since the planets are formed inside a gas and dust disc that surrounds a young star, these conditions are given at distances in which the stellar radiation creates the appropriate temperatures.
In our own solar system, this region is somewhere among the orbits of Jupiter and Uranus. This is remarkable, since Wasp-121b now orbits dangerously close to the surface of its host star, which suggests that, after its formation, it undertook a long trip from the outer frost regions to the center of the planetary system.
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James Webb Space Telescope reveals the origin of the Ultra Hot Explanet Wasp-121b
The silicon was detected in the form of silicon monoxide that reached the planet through rocky material, during the formation of the planet.
The planets are formed from icy powder particles that adhere to each other and gradually grow to become pebbles between a few centimeters and a meter of size that attract gas and small particles that surround them, which accelerates their growth. They are the seeds of future planets such as Wasp-121b.
The study suggests that the planet in formation had cleared its orbit distant from solid pebbles, which stored water in the form of ice, and as a result, the hole prevented other pebbles from reaching the planet.
As the temperature of an atmosphere changes, the amounts of different molecules, such as methane and carbon monoxide, are expected to vary. At the ultra high temperatures of the Diurnal side of Wasp-121b, methane is very unstable and is not present in detectable amounts.
Astronomers have determined that, on planets such as Wasp-121b, the gas hemisphere gas should be mixed with that of the night hemisphere, relatively colder, faster than it takes for the gas composition to adapt to the lowest temperatures.
In this scenario, it would be expected that the abundance of methane was insignificant on the night side, as in the daytime. Therefore, discovering abundant methane on the night side of Wasp-121b, was a surprise.
To explain this result, the equipment proposes that methane gas must be quickly recovered on the night side to maintain its high abundance.
A plausible mechanism for this implies strong vertical currents that raise methane gas from the lower atmospheric layers, which are rich in methane thanks to the relatively low temperatures of the night side, combined with the high proportion of carbon and oxygen of the atmosphere.
“This challenges the dynamic exoplanet models, which will probably have to adapt to reproduce the strong vertical mixture that we have discovered on the night side of Wasp-121B,” says Thomas Evans-Soma, a researcher at the Max Planck of Astronomy and co-author of the studies.
With EFE information.
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