Astronomers detect brightest exoplanet that reflects light ‘like a mirror’

A burning world where metallic clouds rain down drops of titanium, which act “like a mirror”... This is not a science fiction scenario. It is the brightest planet ever detected outside our solar system, the face of which was unveiled by astronomers in a study published Monday, July 10. This strange exoplanet, located more than 260 light years from Earth, reflects 80% of the light of its host star, according to new observations from the European space telescope Cheops. It is the first exoplanet to match the brightness of Venus, the brightest object in our night sky except for the Moon.

Named LTT9779b

Discovered in 2020, this Neptune-sized planet, called LTT9779b, orbits its star in just 19 hours. Because of this proximity, its illuminated face rises to 2,000°C, a temperature considered too high for clouds to form. However, the reflectivity of LTT9779b indicated the presence of clouds. “It was really an enigma”, according to researcher Vivien Parmentier.

The scientists then “considered the formation of these clouds the same way condensation occurs in a bathroom after a hot shower”, explains the researcher in a press release. Like the effect of very hot water in a bathroom, a burning stream of metal and silicate supersaturated LTT9779b’s atmosphere until metallic clouds formed.