WASP-76 b, first discovered in 2013, has been extensively studied due to its many extreme atmospheric features. Previous research, including studies from the UNIGE team, identified phenomena such as iron rain on its night side, barium in its upper atmosphere, and the appearance of a "rainbow" where its day and night sides meet.
"The work on WASP-76 b shows us just how extreme atmospheric conditions can be on ultra-hot Jupiters," commented David Ehrenreich, an associate professor in the Astronomy Department at the UNIGE Faculty of Science and member of the NCCR PlanetS. Ehrenreich, who co-authored the study, added, "In-depth analysis of this type of planet provides us with valuable information for a better understanding of planetary climates as a whole."
Iron Atom Streams Observed
In this new study, the astronomers focused on the day side of WASP-76 b, where the temperature reaches a blistering 2400 degrees Celsius. By conducting high-spectral resolution observations in visible light, they detected a stream of iron atoms rising from the planet's lower to upper atmospheric layers.
"This is the first time that such detailed optical observations have been made on the day side of this exoplanet, providing key data on its atmospheric structure," explained Ana Rita Costa Silva, a doctoral student at the Instituto de Astrofisica e Ciencias do Espaco (IA), currently visiting the Astronomy Department at UNIGE, and the lead author of the study. "Our observations indicate the presence of powerful iron winds, probably fuelled by a hot spot in the atmosphere."
ESPRESSO Spectrograph Enables Discovery
The discovery was made possible through the use of the ESPRESSO spectrograph, which is celebrated for its precision and stability. The instrument, largely developed by UNIGE, is installed on the Very Large Telescope (VLT) in Chile, and its high-resolution spectral capabilities allowed the team to identify the chemical signatures of iron moving through the atmosphere of WASP-76 b. This technique, known as high-resolution emission spectroscopy, is a powerful tool for studying exoplanetary atmospheres.
"ESPRESSO's ability to make such precise measurements is crucial," said Christophe Lovis, an associate professor at UNIGE's Astronomy Department and co-author of the study. "This level of precision allows us to explore the dynamic processes in the atmospheres of exoplanets like WASP-76 b with an unprecedented level of detail."
A New Window Into Exoplanetary Climates
The continuing discoveries on WASP-76 b are laying the foundation for a deeper understanding of exoplanetary climates, particularly for gas giants that experience extreme radiation from their host stars. By mapping atmospheric winds and analyzing their chemical compositions, astronomers are gradually developing comprehensive models of these distant planets' atmospheres. The detection of iron winds on WASP-76 b adds essential data for constructing 3D climate models of this exoplanet, which could eventually help predict similar weather patterns on other planets.
Research Report:ESPRESSO reveals blueshifted neutral iron emission lines on the dayside of WASP-76 b
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