Article by: Andacs Robert Eugen, on 10 July 2023, at 09:17 am PDT

Astronomers have made an intriguing discovery about an exoplanet located over 260 light years away from Earth. This distant world, known as LTT9779b, has been found to be the most reflective planet ever detected outside of our Solar System. Using data from Europe's Cheops space telescope, scientists have determined that this exoplanet reflects an impressive 80 percent of the light emitted by its host star. To put this into perspective, LTT9779b's reflectivity is on par with Venus, the brightest celestial object in our night sky apart from the Moon.

LTT9779b, a Neptune-sized planet, was initially detected in 2020. It completes its orbit around its star in just 19 hours, making it incredibly close to its host. The proximity results in scorching temperatures on the side of the planet facing the star, reaching a blistering 2,000 degrees Celsius. Conventional wisdom suggests that such heat would prevent cloud formation. However, against all expectations, astronomers have observed the presence of clouds on LTT9779b.

This phenomenon has baffled scientists, prompting them to seek an explanation. Vivien Parmentier, a researcher at France's Cote d'Azur Observatory and co-author of a recent study published in Astronomy and Astrophysics, compared the cloud formation to condensation in a steamy bathroom after a hot shower. The intense heat saturates LTT9779b's atmosphere with metal and silicate particles, similar to the substances that make up glass. As a result, metallic clouds form, creating a spectacle of reflective beauty.

LTT9779b is not only extraordinary in terms of its reflectivity but also in its classification. It is an outlier among exoplanets due to its size and orbital characteristics. Typically, planets that orbit their stars in less than 24 hours are either gas giants much larger than Earth or rocky planets half its size. LTT9779b, however, defies these expectations by residing in a region known as the "Neptune desert," where planets of its size are not anticipated to exist. Researchers expressed surprise at its existence, as they initially predicted that its atmosphere would be stripped away by the intense stellar radiation, leaving behind a barren rock.

Curiously, the metallic clouds on LTT9779b play a crucial role in its survival. Acting like a shield, they reflect incoming light and prevent the planet's atmosphere from being blown away. Maximilian Guenther, the project scientist for the Cheops mission at the European Space Agency, likens this protective mechanism to the shields seen in the Star Trek series. This discovery marks a significant milestone, as it offers insight into how a Neptune-sized planet can endure in the inhospitable conditions of the Neptune desert.

The Cheops space telescope, launched by the European Space Agency in 2019, is dedicated to exploring exoplanets beyond our Solar System. In this case, it measured the reflectivity of LTT9779b by observing the changes in light as the planet passed behind its star. This ground-breaking research expands our understanding of exoplanets and provides valuable insights into the diversity of planetary systems across the universe.