An article published in the journal “Astronomy and Astrophysics” reports the first direct observation of an exoplanet using the technique of optical interferometry. The GRAVITY collaboration, so called because the researchers who belong to it manage the work of the instrument with the same name installed on ESO’s Very Large Telescope Interferometer (VLTI), observed the exoplanet HR 8799 e, a super-Jupiter that has a atmosphere containing clouds rich in iron and silicates that swirl around in a storm that crosses the entire planet.
The exoplanet HR 8799 e was discovered in 2010 and is one of four super-Jupiters discovered in the system of the young star HR 8799, which has a mass and a size about 1.5 times the Sun’s and is about 129 light years away from the earth. Those planets are called super-Jupiters because they’re much more massive than Jupiter and therefore represent the last possible step for a planet given that at some point a greater mass leads them into the category of brown dwarfs.
After their discovery, these exoplanets have already been studied but in this new research HR 8799 e was observed using for the first time a direct detection using the technique of optical interferometry that allows to obtain the resolution of a telescope with a diameter of 130 meters. In essence, the GRAVITY instrument exploited four telescopes of ESO’s VLT using them as if they were one, which is precisely the principle of interferometry. This allowed to obtain a spectroscopic analysis about ten times more detailed than in the past observations and therefore for example to obtain more information on its atmosphere’s composition.
Sylvestre Lacour, researcher CNRS at the Observatoire de Paris – PSL and the Max Planck Institute for Extraterrestrial Physics, who led the research team, explained that their analysis showed that the exoplanet HR 8799 e has an atmosphere that contains much more carbon monoxide than methane, a surprising discovery that could be explained by the presence of vertical winds in the upper part of the atmosphere that prevent carbon monoxide from reacting with hydrogen to form methane. Another discovery is that of clouds rich in iron and silicates. All this suggests that there’s a violent storm on the planet that runs through it all.
The impression received by the observations is that of a planet illuminated from within with rays of warm light passing through stormy areas with dark clouds. Convection moves around the clouds of silicates and iron particles, which disintegrate and rain downwards, inside the planet. It0s the portrait of a dynamic atmosphere of a giant exoplanet at birth that is going through complex physical and chemical processes. The age of the star HR 8799 was estimated at around 30 million years so it’s a young star system in astronomical terms.
This research further proves the validity of the GRAVITY instrument in making high quality observations. The possibility of exploiting four VLT telescopes thanks to the technique of interferometry allows to obtain extraordinary results, in this case offering a way to better study exoplanets.
