https://phys.org/news/2021-09-cloud-spo ... lanet.html
by Europlanet
An international team of astronomers has not only detected clouds on the distant exoplanet WASP-127b, but also measured their altitude with unprecedented precision. A presentation by Dr. Romain Allart at the Europlanet Science Congress (EPSC) 2021 shows how, by combining data from a space- and a ground-based telescope, the team has been able to reveal the upper structure of the planet's atmosphere. This paves the way for similar studies of many other faraway worlds.
WASP-127b, located more than 525 light-years away, is a "hot Saturn"—a giant planet similar in mass to Saturn that orbits very close to its sun. The team observed the planet passing in front of its host star to detect patterns that become embedded in the starlight as it is filtered through the planet's atmosphere and altered by the chemical constituents. By combining infrared observations from the ESA/NASA Hubble Space Telescope (HST) and visible light measurements from the ESPRESSO spectrograph at the European Southern Observatory's Very Large Telescope in Chile, the researchers were able to probe different regions of the atmosphere. The results brought a few surprises.
'First, as found before in this type of planet, we detected the presence of sodium, but at a much lower altitude than we were expecting. Second, there were strong water vapor signals in the infrared but none at all at visible wavelengths. This implies that water-vapor at lower levels is being screened by clouds that are opaque at visible wavelengths but transparent in the infrared,' said Allart, of the iREx/Université de Montréal and Université de Genève, who led the study.