2024-07-25 04:00:09
Astronomers have detected signs of water vapor in the atmosphere of a hot Saturn-like exoplanet, designated HD 149026 b and nicknamed Smertrios, using the CARMENES spectrograph at the Calar-Alto Observatory. The discovery, reported in a study, could offer new insights into the structure and formation of this exotic world.
Credit: NASA.
Metal-rich Smertrios orbits the star HD 149026, a yellow subgiant located about 248.5 light-years from Earth. This planet has a radius of 0.81 times that of Jupiter and a mass three times smaller. It completes a full revolution around its star in just 2.876 days at a distance of 0.043 AU, with a temperature equilibrium temperature of 1,693 K. The team led by Sayyed A. Rafi of the University of Tokyo used the CARMENES spectrograph at the Calar-Alto Observatory to obtain high-resolution transmission spectra of Smertrios. Their main goal was to deepen the understanding of the atmospheric composition of this exoplanet.
Transmission spectra are an observation technique used in astronomy to analyze the composition of exoplanet atmospheres. When the light of a star passes through theatmosphere of a transiting planet, certain wavelengths of this light are absorbed by molecules present in the atmosphere. By studying the variations in this absorbed light, scientists can identify the different molecules present, such as water, carbon dioxide where the methane.
Analysis of the CARMENES data revealed a water vapor signal close to the expected location for Smertrios, with a signal-to-noise ratio of 4.8. The researchers note, however, that this signal is a strong indication of the existence of water vapor, but does not definitively confirm it.
The study suggests that the presence of water vapor implies a carbon/oxygen ratio less than one, if the atmosphere is homogeneous and in chemical equilibrium, which implies a low abundance of hydrogen cyanide. However, no traces of hydrogen cyanide were detected, possibly due to the low quality of the dataset.
The researchers also measured Smertrios’ orbital and resting speeds, which were found to be 158.17 km/s and 2.57 km/s, respectively. Although the orbital speed is as expected, the resting speed is strongly redshifted, which could be explained by anomalous atmospheric dynamics or an eccentric orbit.
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