Astrophysicists have proposed to identify a new class of exoplanets - superhot Jupiters. These planets have been observed to exhibit unusual spectral properties, and the atmosphere on their daytime side is more like that of stars than planets. The results are reported in the journal Astronomy and Astrophysics.
Now astroomers have discovered more than a thousand planets around other stars. Many of them were discovered by the transit method, that is, a sign of their existence was a decrease in the brightness of a star at the moment when the planet "shielded" it from the observer. Such an event makes it possible not only to find the planet, but also to study the composition of its atmosphere, since the light of the star passing through it is distorted. Thanks to this, astronomers can estimate the temperature of the atmosphere and the concentration of various substances in it, and in some cases even find indications of the presence of clouds and wind. The spectra of the hottest planets baffled scientists - there were completely no lines that correspond to water vapor, although they are clearly visible in slightly less heated bodies.
In a new work, astrophysicists come to the conclusion that the conditions on such celestial bodies are so extreme that water molecules decay into hydrogen and oxygen. They proposed a model according to which strong winds carry the decaying components of water to the night side of the planets, where they can reconnect due to much lower temperatures and condense into clouds. “The daytime sides of these worlds are more like the atmospheres of stars than planets,” says lead author Vivienne Parmentier of Aix-Marseille University in France. "In a sense, super-hot Jupiters broaden the concept of what kind of body can be considered a planet."
The absence of traces of water in super-hot Jupiters has worried scientists for years. They have already offered various explanations, including those that suggest the exotic chemical composition of such bodies. In the new work, astrophysicists adapted ideas from describing the atmospheres of brown dwarfs, an intermediate type of object between planets and stars. “By doing this, we are bringing our long-standing knowledge from stellar astrophysics into a new field of exoplanet atmospheres,” explains Parmentier.