Astronomers have concluded that the planet Kepler-13A b snows titanium oxide and vanadium oxide, 1,730 light-years from Earth. Modeling showed that this phenomenon is observed only on the night side of a celestial body, where falling snowflakes fall into a "cold trap". The article was published in The Astronomical Journal.
The planet Kepler-13A b in the constellation Lyra was discovered by scientists in 2011. It belongs to the class of hot Jupiters, and its mass is almost three thousand times that of the Earth. Due to the fact that the planet is too close to its parent star, it is always “facing” it - this is called tidal capture. As a result, the daytime side of the planet heats up to very high temperatures, about 2.75 thousand Kelvin. At the same time, the night side of Kepler-13A b always remains cold, and, as scientists have found, there is titanium oxide snow.
It is known that the temperature of the Earth's atmosphere decreases nonuniformly with increasing altitude. In the stratosphere, there is an inversion region where temperatures, on the contrary, begin to rise before continuing to fall again at higher altitudes. The same is true for hot Jupiters, whose daytime side is warmed up to more than 2.5 thousand kelvin. It is believed that titanium oxide (TiO, not to be confused with titanium dioxide TiO2 - the main component of sunscreen) and vanadium (II) oxide are present in the gas envelope of these planets, which absorb light from the parent star, and then re-emit it, heating the surrounding space. However, it turned out that the atmosphere of Kepler-13A b cools uniformly - this is not typical for this class of exoplanets.
The authors of the work carried out observations in the near infrared range using the Wide Field Camera 3 on the Hubble Space Telescope. In addition, they used data from the Kepler space telescope. As a result, the scientists failed to detect signs of temperature inversion, which should have been observed in the Kepler-13A b gas envelope.
Researchers have built a model that explains the behavior of the planet's atmosphere. It turned out that titanium oxide is most likely in a cold trap on the night side. Strong winds on Kepler-13A b carry gaseous matter from one part of the planet to another. When titanium oxide and vanadium oxide hit the night side, they crystallize and collect in clouds. The powerful gravity of the celestial body - six times that of Jupiter - attracts unusual snow, forcing it to sink into the lower atmosphere. There he falls into a cold trap that keeps him in the dark half of the planet.
Scientists' observations support the theory that the gravity of hot tidal planets can create vertical cold traps. “Most of the known hot Jupiters are likely to have precipitation, but the gravity of these giants is not as strong as Kepler-13A b. The titanium oxide snow does not enter the lower atmosphere and is transported back to the daytime side, where it evaporates and turns into gas again,”comments one of the authors of the work.
Cold traps are also found in the solar system, although they are of a different type. On the dwarf planet Ceres, these are craters in which, according to scientists, deposits of water ice are hidden. Similar "cold traps" can also be found near the moon's poles.
Christina Ulasovich
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