Ammonia and water in the atmosphere of the warm Neptune HAT-P-11 b. The study described in the paper: “The GAPS Programme at TNG LV. Multiple molecular species in the atmosphere of HAT-P-11 b and review of the HAT-P-11 planetary system” of M. Basilicata (Università di Tor Vergata)

One of the most interesting possibilities offered by the research on exoplanets is the ability to study types of planets that are not present in the Solar System. Among these are the “hot” and “warm” Neptunes. These are planets the size of Neptune that orbit very close to their stars (with an orbital period shorter than 10 days), with an equilibrium temperature exceeding 1000 K (hot Neptunes) or below this threshold (warm Neptunes).

 

In particular, the study of the atmospheres of such planets is of great interest. This allows for the analysis of the chemical and physical properties of atmospheres in conditions not observed in the Solar System. Additionally, by determining the abundance ratios of chemical elements with respect to hydrogen, it is possible to derive important information on the formation and evolution of these planets. For instance, if these planets formed at larger distances from their stars and then moved inward, they could absorb solids and planetesimals during this migration, altering their chemical composition and thus the chemical abundances of their atmospheres.

 

In the framework of the international program GAPS (Global Architecture of Planetary Systems), the team led by the astronomer M. Basilicata (University of Tor Vergata and INAF – Astrophysical Observatory of Turin) analyzed new observations and archival data of the transiting planetary system around the K4V star HAT-P-11, which is about 6 billion years old. The new observations were acquired with the high-resolution infrared spectrograph GIANO-B, mounted on the Telescopio Nazionale Galileo. The archival data were taken with NASA’s planet-hunting satellite Kepler.

This extensive set of data has allowed the astronomers to determine the orbital parameters of the planet HAT-P-11 b, which are necessary for correctly modeling its atmosphere. Furthermore, the spectroscopic observations have allowed a significant detection of the presence of water and ammonia in the planet’s atmosphere, along with the possible detection of six other molecules, including carbon dioxide and methane. These observations are compatible with two possible models: an atmosphere with an abundance of elements heavier than hydrogen (metallicity) greater than that of the Sun, or a non-equilibrium chemistry with low metallicity but with solar-like carbon-to-oxygen and nitrogen-to-oxygen abundance ratios.

The study is described in the paper: “The GAPS Programme at TNG LV. Multiple molecular species in the atmosphere of HAT-P-11 b and review of the HAT-P-11 planetary system“, recently published in Astronomy and Astrophysics. The list of coauthors includes the astronomers A. Maggio and G. Micela of INAF – Astronomical Observatory of Palermo.

 

The cover figure (click here to visualize it entirely) shows a DSS-2 image of the field around HAT-P-11, the star at the center.

 

Mario Giuseppe Guarcello  ( follow mariospiegacose) ( mariospiegacose) ( follow mariospiegacose)

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