A team of researchers from different institutions in the United Kingdom and the United States coordinated by experts from Pennsylvania State University has discovered an extrasolar planet in which titanium dioxide, one of the main compounds of sunscreen, is snowing. The data provided by the Hubble Space Telescope have made it possible to determine that these precipitations only take place in a region of this object where it is permanently at night, but they do not occur in the illuminated area.
This extrasolar world, called Kepler-13Ab, lies 1,730 light-years away, and is a gas giant of a variety known as hot Jupiter. These stars orbit much closer to their star than Mercury does to the Sun; Kepler-13Ab, which is five to eight times more massive than the largest of the planets in our Solar System, makes a complete revolution around it in less than two days.
In his case, in addition, the gravitational pull of the star makes a part always remain oriented towards it. Temperatures of 2,760 degrees are reached here, making it one of the hottest exoplanets known . In the other, on the contrary, darkness always reigns.
As indicated by its discoverers in a statement, it is the first detection of a process of this type in an extrasolar world, and is one more example of the complexity of the atmospheric processes that we can find on exoplanets.
In addition, they hope that their work could be useful in studying the habitability of other bodies more similar to the Earth.
Thus, Thomas G. Beatty, professor of Astronomy at the aforementioned US institution, who has coordinated this initiative, points out that studies with these types of gaseous worlds can lay the foundations for research focused on other terrestrial planets. “The more we know about their atmospheres and their behavior, the more we will advance in our knowledge of the smaller planets and with more complex layers of gases,” he says.
An exotic world
In an essay published in The Astronomical Journal , Beatty and his collaborators indicate that, in principle, their objective was not to specifically look for the aforementioned titanium dioxide , but to find out why the atmosphere of Kepler-13Ab becomes colder at higher altitudes. , a phenomenon completely different from what happens in other hot Jupiters. In them, the titanium oxides absorb the light radiation and radiate it again in the form of heat.
In fact, the atmosphere of the gas giants of the solar system, which are much cooler, becomes more temperate at higher altitudes.
Beatty’s group concluded that these oxides had disappeared from the atmosphere of the planet’s daytime zone, probably blown away by strong winds that carry them to the night side. There they condense into flakes and clouds, and fall as if it were snow. However, the intense surface gravity of the planet pulls it from the upper layers of the atmosphere and carries it to the lower ones, where it is trapped.
“Climate on other worlds is a complex puzzle, and being able to observe this process provides us with a very important piece,” says astronomer Jason Wright, from Pennsylvania State University, who has also participated in this initiative.
“The observations give us clues about the formation of clouds on these types of planets and the role that gravity plays in the composition of their atmosphere,” adds Beatty.
“Probably this same type of precipitation occurs in most hot Jupiters , but the surface gravity of those that have been studied so far is lower than that of Kepler-13Ab. In them, the titanium oxides do not fall as much far away, they do so in warmer areas, where they evaporate again and regain their gaseous form “, he concludes.
Reference: ‘Evidence for Atmospheric Cold-trap Processes in the Noninverted Emission Spectrum of Kepler-13Ab Using HST / WFC3’. Thomas G. Beatty et al. The Astronomical Journal. Volume 154, Number 4. http://dx.doi.org/10.3847/1538-3881/aa899b
Image: NASA / ESA / G. Bacon (STScI)
