Evidence for the presence of water vapor in the atmosphere of Smertrios

Using the CARMENES spectrograph, astronomers have found evidence of water vapor in the atmosphere of a hot Saturnian exoplanet HD 149026 b, called Smertrios. This finding is reported in a research paper published on the preprint server arXivcould be the key to a better understanding of the structure and formation scenario of this alien world.

Smertrios is a hot, metal-rich Saturn orbiting HD 149026, a yellow subgiant star of spectral type G0 IV, about 248.5 light-years away. The planet has a radius of about 0.81 that of Jupiter and is approximately three times less massive than Jupiter. Previous observations found that Smertrios orbits its host every 2.876 days, about 0.043 AU away. The equilibrium temperature of the planet is estimated to be 1,693 K.

A team of astronomers led by Sayyed A. Rafi of the University of Tokyo in Japan employed CARMENES at the Calar-Alto Observatory to perform high-resolution cross-correlation spectroscopy of Smertrios. Their main goal was to get more information about the composition of the atmosphere of this exoplanet.

“Transmission spectroscopy represents one of the most successful approaches for studying exoplanet atmospheres. We analyzed the high-resolution near-infrared transmission spectrum of hot Saturn, HD 149026 b, taken with the CARMENES spectrograph,” the researchers wrote in the paper.

Analyzing the CARMENES data, Rafi’s team found evidence of a water signal very close to the expected location of Smertrios. The strongest signal had a signal-to-noise ratio (S/N) of 4.8. Astronomers noted that the detected signal can only be considered evidence of the existence of water vapor at this time, not a confirmed detection.

According to the study, evidence of water vapor in the atmosphere of Smertrios suggests that the carbon-to-oxygen ratio of the planet must be less than one if the atmosphere is homogeneous and in chemical equilibrium, as the amount of hydrogen cyanide is expected to be very low.

Although scientists searched for hydrogen cyanide in the atmosphere of Smertrios, they found no evidence of the compound. Astronomers speculate that this may be due to the relatively low S/N data set. Therefore, the possibility of hydrogen cyanide in the atmosphere of this planet cannot be definitively ruled out.

The study also measured the orbital and rest velocities of Smertrios, which were found to be approximately 158.17 and 2.57 km/s. However, it is found that while the orbital velocity is consistent with the expected value, the rest velocity is significantly redshifted. The authors of the paper concluded that this could be explained by several scenarios, such as anomalous atmospheric dynamics or an orbit with a non-zero eccentricity.

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