Using data from the European Space Agency’s (ESA) Cheops satellite, astronomers discovered the most reflective planet yet discovered. When viewed by observatories, the planet is covered in a dense layer of reflecting metal clouds, effectively turning it into a massive mirror.

Venus has a dense cloud layer that reflects approximately 75% of the Sun’s radiation. This is why, after the Moon, it is the brightest object in the night sky. To put this in context, the Earth only reflects about 30% of the incoming sunlight. What about the recently discovered planet LTT9779 b? It reflects an astounding 80% of the light emitted by its host star.


This exoplanet is roughly the size of Neptune, making it the universe’s largest mirror, according to ESA. The metallic clouds are largely formed of silicate, which is also found in sand and glass. Other metals, such as titanium, are also present in the clouds. The exoplanet is so near to its home star that it completes an orbit in under a day.

The journal Astronomy & Astrophysics has published a study on the planet and its unique features. The burning planet is quite close to its stars and has massive clouds of metal floating around while raining titanium drops.

“It was quite perplexing at first, until we realised we should think of cloud formation in the same way we think of condensation forming in a bathroom after a hot shower.” To steam up a bathroom, either chill the air until water vapour condenses or run hot water until clouds develop because the air is so saturated with vapour that it just cannot hold any more. Similarly, despite being so hot, LTT9779 b can create metallic clouds because the atmosphere is oversaturated with silicate and metal vapours,” noted Vivien Parmentiar, co-author of the study, in a press release. Parmentier works as a researcher at the Côte d’Azur Observatory in France.

Because of its size and warmth, the planet is known as a “ultra-hot neptune.” According to Parmentiar, no other such planet has been discovered to circle so near to its host star, and it is a “planet that shouldn’t exist,” because such planets’ atmospheres are expected to be driven away by their star, leaving bare rock.
The experts believe that the metal clouds are the reason the planet is still alive. The clouds reflect a large portion of the starlight, keeping the planet’s atmosphere from becoming too heated and evaporating. Metals also indicate that the atmosphere is too dense to be blown away.

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