Astronomers find water vapor on hot exoplanet Cuancoá

Astronomers using the James Webb Space Telescope have made a remarkable discovery regarding the atmosphere of an extremely hot exoplanet called LTT 9779 b, also known as Cuancoá. This planet orbits its star every 19 hours and is categorized as an ultra-hot Neptune. Discovered in 2020, Cuancoá has a mass about 29 times that of Earth and is part of a rare group of planets known as the "hot Neptune desert." The researchers detected water vapor and thick clouds in Cuancoá's atmosphere, which is astonishing given the planet's close proximity to its star. One scientist compared the discovery to finding a snowball that has not melted in a fire. This finding highlights the diversity of planetary systems and how they evolve under extreme conditions. The team utilized a special mode of the telescope to study the exoplanet. This technique, called Single Object Slitless Spectroscopy, helps analyze light in the near-infrared range. It allows scientists to gather more detailed information about exoplanets than previously possible. For Cuancoá, the researchers could identify water vapor and examine the light reflected from its clouds. Cuancoá is tidally locked, meaning one side constantly faces its star, with temperatures soaring up to 3,600 degrees Fahrenheit. Meanwhile, the other side remains in permanent darkness. The temperature differences between the day and night sides create strong atmospheric circulation, leading to a powerful eastward-flowing jet stream. The study revealed that the clouds on Cuancoá's dayside are formed when hot air rises while cooler air sinks on the night side. The planet's high reflectivity is also due to a unique atmospheric composition. Researchers believe this high albedo, or sunlight reflection, may affect the planet's energy balance. The detection of water vapor confirms that it is possible to study the atmospheres of cloudy exoplanets by examining the heat they emit. The findings suggest the planet's clouds and high reflectivity are tied to its atmospheric behavior. The research team continues to refine their models and gather more observations to deepen their understanding of Cuancoá's atmosphere and weather patterns. They are combining data from other telescopes to learn as much as possible about the planet.