Water detected on Saturn-like planet named Smertrios

Imagine a far-off planet, not too different from Saturn, but with a twist. This is HD 149026 b, charmingly known as Smertrios.

A team of astronomers led by Sayyed A. Rafi of the University of Tokyo recently took a closer look at the mysterious atmosphere of Smertrios.

Curious case of Smertrios

Smertrios is a metal-rich hot Saturn planet that plays the orbiting game around a yellow subgiant star, HD 149026.

Positioned quite comfortably at a distance of about 248.5 light-years from us, it’s a fascinating celestial object that we’re still trying to understand.

This cosmic giant, though less massive, is about 0.81 times the size of Jupiter. It orbits its host star every 2.876 days from a distance of 0.043 AU.

And if it could boast about one thing, it would be its sizzling equilibrium temperature – a whopping 1,693 Kelvin.

Drops of water on Smertrios?

The ultimate goal of the astronomers was to comprehend the composition of Smertrios’s atmosphere.

“Transmission spectroscopy presents one of the most successful approaches for investigating the atmospheres of exoplanets,” the scientists noted.

“We analyzed the near-infrared high-resolution transmission spectrum of a hot Saturn, HD 149026 b, taken using CARMENES spectrograph.”

The team found a water signal very close to where Smertrios should be. With a signal-to-noise (S/N) ratio of 4.8, it was a discovery they could not ignore.

However, the experts pointed out that this signal is only evidence — not a confirmation — of water vapor.

A tell-tale sign for the scientists was that Smertrios’s carbon to oxygen ratio must be less than one. This is because the hydrogen cyanide abundance, expected to be very low if the atmosphere is homogeneous, depends on this ratio.

While the scientists did look for hydrogen cyanide, they did not find any evidence. This, they believe, could be due to the low S/N dataset, so the presence of hydrogen cyanide cannot be entirely ruled out just yet.

Measuring the inexplicable

The study also ventured into measuring the orbital and rest velocities of Smertrios. They clocked in at about 158.17 and 2.57 km/s, respectively.

What’s intriguing, though, is that the orbital velocity matched the expectations, but the rest velocity was highly red-shifted.

This anomaly could be due to a variety of scenarios, such as peculiar atmospheric dynamics or an orbit with non-zero eccentricity.

Role of metallicity

Metallicity refers to the abundance of elements heavier than hydrogen and helium in a celestial object’s atmosphere. Smertrios’s high metallicity is an intriguing trait that’s captured astronomers’ imaginations.

Why is this important? High metallicity can shape a planet’s formation, structure, and even its atmosphere.

By exploring Smertrios’s metal-rich nature, we might uncover secrets about how planets form in metal-heavy environments.

This could reveal fascinating connections between a star’s metal content and the types of planets that orbit it.

Implications for exoplanetary atmospheres

Detecting possible water vapor in Smertrios’s atmosphere changes how we understand exoplanet atmospheres.

Water is vital in our hunt for habitable environments since it’s crucial for many chemical and physical processes.

While Smertrios is much too hot to support life as we know it, finding water vapor hints at similar processes happening on more temperate exoplanets.

This discovery encourages us to dive deeper into studying exoplanet atmospheres, helping us better grasp the diverse atmospheric compositions and dynamics throughout the galaxy.

The study is published in the preprint server arXiv.

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