Two hot Jupiters with a water-rich atmosphere. The study: “The GAPS Programme at TNG LXVII. Detection of water and preliminary characterisation of the atmospheres of the two hot Jupiters KELT-8 b and KELT-23 Ab” of M. Basilicata (University of Tor Vergata) appeared su A&A)
Observations carried out with the Telescopio Nazionale Galileo of two exoplanets belonging to the hot Jupiter class reveal an atmosphere rich in water, despite the high temperatures.
Water is an essential ingredient for life as we know it—not only because we drink it, but because it is an exceptional solvent for the chemical processes that underlie life on Earth. It is therefore no surprise that detecting the presence of water in planets orbiting other stars, or in protoplanetary disks where planets form, is of primary importance.
Among the various known classes of exoplanets, hot Jupiters—gas giants in close orbits around their stars, with equilibrium temperatures exceeding 1000 K—are of great interest for the study of planetary atmospheres. This is for two reasons. First, this class of planets does not exist in the Solar System, making them an exceptional laboratory for atmospheric physics. Second, their high equilibrium temperatures result in an extended atmosphere, which facilitates observations based on the fraction of stellar radiation intercepted by the planetary atmosphere (transmission spectroscopy).
As part of the GAPS (Global Architecture of Planetary Systems) project, a team of researchers led by astrophysicist M. Basilicata (University of Rome “Tor Vergata”) studied and characterized the atmospheres of the hot Jupiters KELT-8b and KELT-23Ab. This was achieved using near-infrared observations obtained with the GIANO-B spectrograph, mounted on the Telescopio Nazionale Galileo. The observations, compared with multiple atmospheric models, revealed an atmosphere rich in water despite the high equilibrium temperatures. Other properties measured by the researchers, such as the chemical abundances of carbon and oxygen, also provided important information about the formation sites of the two planets. Their formation likely occurred within the water condensation line in the protoplanetary disk—the transition region where water changes from gas to ice.
The study is described in the article “The GAPS Programme at TNG LXVII. Detection of water and a preliminary characterization of the atmospheres of the two hot Jupiters: KELT-8b and KELT-23Ab“ recently published in the journal Astronomy and Astrophysics. The study also involved astrophysicists M. d’Arpa and S. Colombo from INAF – Osservatorio Astronomico di Palermo.
The figure (click here to view it in full) shows an optical image of the binary system KELT-23. The primary component of the system (KELT-23 A) hosts one of the two hot Jupiters analyzed in this study.
Mario Giuseppe Guarcello
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