Scientists are puzzled by a “mirror” planet that is raining titanium and should not exist

This strange exoplanet reflects 80% of the light from the star it orbits, which is an incredible amount without considering that Earth only manages 30% of it. Discovered in 2020, this Neptune-sized planet is called LTT9779b and orbits its star in just 19 hours. Because of this proximity, the temperature of its luminous face rises to 2,000 degrees, a temperature considered too high for clouds to form. However, the reflectivity of LTT9779b indicates its presence. “It was really a mystery,” says Vivian Parmentier, a researcher at the Côte d’Azur Observatory (France) and co-author of the study.

The expert explained in a statement that the researchers considered the formation of these clouds “in the same way that condensation occurs in the bathroom after a hot shower.” Like the effect of very hot water in a shower, a smoldering stream of mineral and silicates — made of the material of glass — saturates LTT9779b’s atmosphere until metallic clouds form.

More surprises

But the planet had other surprises in store. To date, the only exoplanets known to orbit their star very quickly (in less than 24 hours) are gas giants 10 times the size of Earth or rocky planets half their size.

But LTT9779b is about five times the size of Earth and is located in an area astronomers call the “hot Neptune desert,” where planets of this size “shouldn’t exist,” Parmenter summarizes.

In addition, astronomers did not expect to find any kind of atmosphere on this exoplanet due to its proximity to the star, which would normally “pull out” any type of gaseous formation.

After much searching they found the explanation: “LTT9779b’s metallic clouds act like a mirror,” reflecting light and preventing the atmosphere from disintegrating, according to Maximilian Ginter, chief scientist on the Khufu project at the European Space Agency (ESA). They act “a bit like a shield,” he told AFP, like the ones that protect “spaceships in old Star Trek episodes.”

The scientist added that this research represents an “important step” because it shows how a planet the size of Neptune can survive in such an environment.

The European Space Agency’s Khufu telescope was sent into space in 2019 to explore discovered planets outside the solar system. He measured the reflective power of LTT9779b by comparing the light before and after the exoplanet disappeared behind its star.