An international team, made up of scientists from the Institute of Astrophysics of the Spanish Atlantic archipelago of the Canary Islands (IAC), identified water vapor in the atmosphere of WASP-18bwhich is an ultrahot gas giant extrasolar planet, the IAC reported on Wednesday.
The planet WASP-18bwhich is about 400 light-years from Earth, is ten times larger than Jupiter and has an orbital period of less than one day, it is indicated in a statement in which it is added that the finding is published in the nature magazine.
The extreme proximity to which it is located from its star, its relative proximity to Earth and its great mass, have made it, since its discovery in 2009, a coveted research object, explains the IAC.
Now, observations made with the James Webb Space Telescope (JWST)) made it possible to produce the most detailed map to date of a gas giant planet.
“It was a great feeling to look at the JWST spectrum of WASP-18 for the first time by seeing the subtle, but precisely measured signature of the water,” says Louis-Philippe Coulombe, a graduate student at the University of Montreal and lead author of the paper. article.
With this type of measurement, “we will be able to detect this type of molecule on a wide range of planets in the coming years,” he says.
For the study of WASP-18 b, the team mapped its temperature or luminosity by detecting the secondary eclipse, that is, the moment when the planet slips behind its star and reappears, and studied the thermal differences along its daytime hemisphere, the side that always faces the star.
The mapping obtained by the JWST shows a “huge” change in temperature, from up to 1,000 degrees Celsiusfrom the hottest point on the face facing the star to the so-called terminator, or transition line between the illuminated part and the shadow part of the planet, which are in a permanent twilight.
Since the planet is much colder in the terminator, the scientific team suspects the existence of a strong magnetic field that would be preventing the winds from effectively distributing the heat towards the night side.
In this way, the winds would be blowing from the center of the planet towards the north and south poles, instead of from east to west as might be expected.
The IAC says that the study, which has also recorded thermal changes at different levels of the planet’s atmosphere, has found slight traces of water vapor at different heightsdespite the fact that the temperatures are almost 2,700 °C and such extreme heat would break most of the water molecules.
The ability to detect such a small number of these molecules demonstrates the extraordinary sensitivity of the JWST.
In the words of Enric Pallé, IAC researcher and co-author of the study: “When analyzing the spectrum of WASP-18bwe not only learn about the various molecules that can be found in its atmosphere, but also about how it was formed.”
He adds that, according to his observations, WASP-18b’s composition is very similar to that of its star, which means that it probably formed from the remnants of gas left behind just after its birth.