You will also be interested
[EN VIDÉO] The James Webb Space Telescope has already discovered alien Dyson spheres! Corridor noise reports very interesting recent observations of the observatory …
Some call it a super earth. Others from Mini Neptune. What is certain is that Gliese 1214 b (GJ 1214 b) is an exoplanet that is about 40 light years away from our solar system. The Hubble Space Telescope had seen it as a largely gaseous planet, possibly with a large amount of water in its atmosphere. And the James Webb Space TelescopeJames Webb Space Telescope (JWST) has just provided some details on it.
A team led by researchers from the University of Maryland (USA) actually tracked GJ 1214 b in almost orbit around its star – barely 40 hours. Using JWST’s powerful mid-infrared (MiriMiri) instrument. Enough that they can finally see through the clouds and fog that surrounds the planet. To measure how it emits heat, both day and night side.
A confusing planet
It’s precisely the contrast between the day and night sides – which is always the same on this so-called “locked” planet – that leads astronomers to believe that GJ 1214 b’s atmosphere is not composed mostly of hydrogen (H2) molecules. But slightly heavier molecules such as water (H2O) or methane (CH4). Water vapor — because GJ 1214 b is too hot to keep water in its liquid state — likely, the researchers say. Even if you can’t be sure at the moment.
Astronomers are also finding that the exoplanet is colder than they thought. The sign that its atmosphere reflects much of its star’s light. “Not everything that makes up the nebulae or clouds of this planet is what we expect. It’s brilliant, it’s thought-provoking, and it’s bewildering and surprising,” said Eliza Kempton, lead author of the study, in a University of Chicago press release. “This will point us to many more studies to understand what it could be.” »
We also want to try to understand whether, as these clues suggest, GJ 1214 b formed further away from its host as a red dwarf and then converged on its current orbit. This is all the more important as mini Neptunes could be the most common class of exoplanets in our Milky Way.
SuperEarth Gliese 1214 has a water-rich atmosphere
We know the mass and size of the exoplanet Gliese 1214 b and thus its density. It is indeed a super earth super earth, but we do not know its true nature. Rocky planet degasser Rocky planet with hydrogen-rich atmosphere? Did Mini Neptune Emigrate? planet oceanplanet ocean? The Subaru telescope has just revealed new evidence supporting the hypothesis that its atmosphere is rich in water.
Article by Laurent SaccoLaurent Sacco published on 09/08/2013
With the Japanese Subaru telescope, the chemical composition of the atmosphere of the super-Earth Gliese 1214 b could be examined again. His surname comes from his star, which bears number 1,214 in the Gliese-Jahreiss catalog (named after astronomers Wilhelm Gliese and Hartmut Jahreiss), which attempts to list all the stars that are within 25 parsec sparsecs of Earth.
We have known since 2009 that a super-Earth orbits this star. It’s called GJ 1214 b, has a radius about 2.6 times Earth’s radius, and is about 6.5 times more massive. Its discovery is thanks to the Harps (High Accuracy Radial Velocity Planet Searcher) instrument, a spectrometer on ESO’s 3.6-metre telescope in Chile, which is also responsible for other finds, such as the around Gliese 581.
This time, the astrophysicists studied Gliese 1214 b using the planetary transit method, while Harps used the radial velocity method. To do this, they used two instruments that observe in the visible and are equipped with a blue filter: the Suprime-Cam and the Faint Object Camera and Spectrograph (Focas), which are attached to the Subaru telescope.
Rayleigh scattering, a key to the atmosphere of exoplanets
To constrain super-Earth’s chemical makeup, they looked for traces of strong Rayleigh scattering in light penetrating the atmosphere of Gliese 1214 b as it passes in front of its parent star.
Remember that Rayleigh scattering is due to gas molecules (O2, N2, CO2, water vapor, etc.) or fine dust particles present in the atmosphere. It occurs when the size of the scattering molecules is much smaller than the wavelength of the radiation.
Since the intensity of the scattered light is inversely proportional to the power 4 of the wavelength of the incident radiation, it occurs particularly at the shorter wavelengths of the spectrum. This partly explains the blue color of the sky during the day. Rayleigh scattering is named after the Nobel Prize in Physics John William Strutt, third Baron Rayleigh, better known by his title Lord Rayleigh, who studied wave phenomena extensively.
Probably no hydrogen in the atmosphere of Gliese 1214 BC
If the atmosphere of an exoplanet consists mainly of hydrogen, then during the transit in front of the star one must observe a sharp characteristic drop in the intensity of the light in a wavelength band associated with the color blue. This would be evidence for the existence of strong Rayleigh scattering associated with hydrogen. On the other hand, if the atmosphere is water-rich or if there is heavy cloud cover, strong Rayleigh scattering should not be observed.
However, as explained in the article the astrophysicists have deposited on arxiv, no significant traces of Rayleigh scattering were detected by the Subaru instruments. The researchers cannot completely rule out that the super-Earth still has a hydrogen-rich atmosphere but significant cloud cover. However, combining this study with other previously conducted investigations makes it increasingly likely that Gliese 1214 b does in fact have a water-rich atmosphere.
However, we know that if this is indeed the case and the temperature of the atmosphere of Gliese 1214 b exceeds 100 °C, then it cannot be an Earth-like world. We may have to wait until Tess is commissioned to discover one…