2023-05-11 18:21:15
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[EN VIDÉO] The James-Webb Space Telescope has already detected extraterrestrial Dyson Spheres! Corridor noises report very intriguing recent observations from the observatory…
Some call it a super-Earth. Others of mini-Neptune. What is certain is that Gliese 1214 b (GJ 1214 b) is a exoplanetexoplanet located some 40 light years from our solar system. THE télescope spatial Hubbletélescope spatial Hubble had seen it as a largely gaseous planet whoseatmosphereatmosphere may contain a large amount of water. And the télescope spatial James-Webbtélescope spatial James-Webb (JWST) has just provided some details regarding it.
A team led by University of Maryland researchers (United States) indeed followed GJ 1214 b almost on a orbitorbit whole around his starstar – barely 40 hours. With the mighty instrument infraredinfrared AVERAGE (MiriMiri) of the JWST. Enough to allow them to finally see through the cloudsclouds and mist that surround the planet. To measure how it emits heatheaton its day side and on its night side.
A confusing planet
It is precisely the contrastcontrast noted between the day side and the night side – always the same for this so-called planet “locked” – which makes people say astronomersastronomers that the atmosphere of GJ 1214 b is not mainly composed of moleculesmolecules of hydrogen (H2). But rather slightly heavier molecules like water (H2O) or methane (CH4). Water vapor – because GJ 1214 b is too hot to maintain water in its liquid state – probably, say the researchers. Even if they can’t be sure right now.
Astronomers also note that the exoplanet is colder than they imagined. The sign that its atmosphere reflects a large part of the light of its star. “Not everything that makes up the mists or clouds of this planet is what we expected. It’s brilliant, it’s reflective and it’s puzzling and surprising”comments Eliza Kempton, lead author of the study in a statement from the university of chicago (UNITED STATES). “This is going to point us towards many more studies to try to understand what it might be. »
To also try to understand if, as these clues suggest, GJ 1214 b formed at a more distant distance from its red dwarf host and then moved closer to its current orbit. This is all the more important since mini-Neptunes might be the most common class of exoplanets in our Milky WayMilky Way.
SuperEarth Gliese 1214 has a water-rich atmosphere
We know the massemasse and the size of the exoplanet Gliese 1214 b and therefore its density. It’s a good one superTerresuperTerre but we do not know its true nature. rocky planetrocky planet degassed with a hydrogen-rich atmosphere? mini-Neptune having migrated? planet oceanplanet ocean ? The Subaru telescope has just provided new evidence supporting the hypothesis that its atmosphere is rich in water.
Article of Laurent SaccoLaurent Sacco published on 08/09/2013
The chemical composition of the atmosphere of the super-Earth Gliese 1214 b might be probed once more using the Japanese telescope Subaru. His surname comes from his star, which porteporte number 1.214 in the Gliese-Jahreiss catalog (named following astronomers Wilhelm Gliese and Hartmut Jahreiss) which attempts to list all stars within 25 parsecsparsecs of the earth.
Since 2009, we know that a super-Earth is in orbit around this star. Called GJ 1214 b, it has a radius of regarding 2.6 times that of Earth and is regarding 6.5 times more massive. Its discovery is due to the Harps instrument (High Accuracy Radial Velocity Planet Searcher), and spectrometerspectrometer equipping the 3.6-meter telescope of the ESO in Chile, at the origin of other finds, such as those made around Gliese 581.
This time the astrophysicistsastrophysicists studied Gliese 1214 b using the planetary transit method while Harps uses that of gearsgears radial. For this, they used two instruments observing in the visible and equipped with a blue filter, the Suppress-Cam and the Faint Object Camera and Spectrograph (Focas) fitted to the Subaru telescope.
Rayleigh scattering, a key to the atmospheres of exoplanets
In order to put constraints on the chemical composition of the super-Earth, they went hunting for traces of diffusiondiffusion Rayleigh strong in the light passing through the atmosphere of Gliese 1214 b as it transits in front of its host star.
Recall that Rayleigh scattering is due to gaseous molecules present in the atmosphere (O2N2CO2, steam, etc.) or fine dust particles. It occurs when the size of the diffusing molecules is much smaller than the wave lengthwave length radiation.
As the intensity of the scattered light is inversely proportional to the power 4 of the wavelength of the incident radiation, it occurs especially for the shorter wavelengths of the spectrespectre. This partly explains the blue color of the sky during the day. Rayleigh scattering is named following the Nobel Prize for physiquephysique John William Strutt, third Baron Rayleigh, better known by his title Lord Rayleigh, who worked extensively on wave phenomena.
Probably no hydrogen in the atmosphere of Gliese 1214 b
If the atmosphere of an exoplanet is mainly composed of hydrogen, one must observe, during the transittransit in front of the star, a characteristic sharp drop in the intensity of light in a band of wavelengths associated with the color blue. This would be proof of the existence of strong Rayleigh scattering associated with hydrogen. On the other hand, if the atmosphere is rich in water or if there is significant cloud cover, strong Rayleigh scattering should not be observed.
However, as explained in the article that the astrophysicists have deposited on arxiv, no significant trace of Rayleigh scattering was detected by Subaru’s instruments. The researchers cannot completely rule out that the super-Earth still has a hydrogen-rich atmosphere but with significant cloud cover. However, by combining this study with others carried out previously, it becomes more and more likely that Gliese 1214 b does indeed have a water-rich atmosphere.
We know, however, that if this is indeed the case, the temperature of the atmosphere of Gliese 1214 b exceeding 100°C, it cannot be a world resembling Earth. We may have to wait for Tess to be put into service to discover one…
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