Data from European Space Agency’s Cheops mission indicates that the ultra-hot exoplanet, LTT9779b, reflects 80% of light from its host star (more than Venus, which reflects about 75% of light from sun).
ESA’s Cheops
CHaracterising ExOPlanet Satellite is the first exoplanet follow-up mission. It was launched in December 19,2019 with a planned mission duration of 3.5 years. The mission was extended to 2026 in 2023. It is the first small-class mission in ESA’s Cosmic vision, campaign of science and space exploration missions in the Science Programme of ESA. Its goal is to study bright, nearby stars that are known to be orbited by their own planets.
LTT9779b and New Findings
LTT9779b is a Neptune-sized exoplanet which is more than 260 light years from earth. Discovered in 2020, the exoplanet takes only 0.8 days (19 hours) to complete one orbit of its host star, LTT9779. Since it is too close to its host star, the side facing the star has a temperature around 2000 0C and this would make formation of clouds impossible. But clouds are still present in LTT9779b.
Vivien Parmentier, researcher at France’s Cote d’Azur Observatory and co-author of the study says that the cloud formation should be seen in the same way as condensation formation in bathroom after a hot shower. Similar to running hot water that steams up the bathroom, a scorching stream of metal and silicate oversaturate the atmosphere of this exoplanet until metallic clouds are formed.
The exoplanet LTT9779b is found in a region called the ‘Neptune Desert’, where planets its size are not supposed to be present. According to Parmentier, for planets like LTT9779b, the atmosphere is expected to be blown away by their star, leaving behind bare rock.
From the words of first author Sergio Hoyer of the Marseille Astrophysics Laboratory, it is evident that the researchers believe that the metallic clouds help LTT9779b to survive in the hot Neptune Desert. The clouds reflect light and avoids the planet getting too hot and evaporating. Also, being highly metallic makes the planet and its atmosphere heavy and harder to blow away.
The planet’s initial discovery and characterization was done by NASA’s TESS mission (first-ever spaceborne all-sky transit survey) and ground-based instruments such as the ESO (European Southern Observatory) HARPS (High Accuracy Radial velocity Planet Searcher) instrument in Chile. Cheops high precision measurements were a targeted follow-up from this.
