Evidence of water vapor detected in Smertrio’s atmosphere

Using the CARMENES spectrograph, astronomers have found evidence of water vapor in the atmosphere of a hot Saturnian exoplanet designated HD 149026 b, called Smertrios. The finding, reported in a research paper published on the preprint server arXivmay 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 Jupiter radii and is roughly three times less massive than Jupiter. Previous observations have revealed that Smertrios orbits its host every 2,876 days, about 0.043 AU from it. The equilibrium temperature of the planet is estimated to be 1,693 K.

The 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 gain more insight into the composition of the exoplanet’s atmosphere.

“Transmission spectroscopy represents one of the most successful approaches for probing exoplanet atmospheres. We analyzed the high-resolution near-infrared transmission spectrum of a hot Saturn, HD 149026 b, obtained using the CARMENES spectrograph,” they write paper researchers.

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

According to the study, evidence of water vapor in Smertrio’s atmosphere suggests that the planet’s carbon-to-oxygen ratio should be less than one if the atmosphere is homogeneous and in chemical equilibrium, since the abundance of hydrogen cyanide is expected to be very low. .

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

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

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