Astronomers have identified the most reflective exoplanet ever observed outside of our Solar System. This planet, named LTT9779b, is located more than 260 light years away from Earth and reflects 80 percent of the light from its host star. The observations were made using Europe’s exoplanet-probing Cheops space telescope. This makes LTT9779b the first exoplanet to be as shiny as Venus, which is the brightest object in our night sky after the Moon.
LTT9779b is a Neptune-sized planet that was first discovered in 2020. It orbits its star in just 19 hours, making it extremely close. The side of the planet facing its star reaches temperatures of 2,000 degrees Celsius, which is too hot for clouds to form. However, the researchers found that LTT9779b has clouds made of metal and silicate, similar to the condensation that forms in a bathroom after a hot shower.
The planet’s ability to form clouds in such extreme conditions is puzzling to scientists. LTT9779b is also an outlier in terms of its size and location. It is around five times the size of Earth and resides in a region known as the “Neptune desert,” where planets of its size are not expected to be found. Normally, planets in this region would have their atmosphere blown away by their star, leaving behind bare rock. However, LTT9779b’s metallic clouds act as a shield, reflecting away light and preventing the atmosphere from being blown away.
The discovery of LTT9779b is significant because it shows how a Neptune-sized planet can survive in the Neptune desert. The European Space Agency’s Cheops space telescope, launched in 2019, played a crucial role in measuring the reflectiveness of LTT9779b. By comparing the light before and after the exoplanet disappeared behind its star, astronomers were able to determine its reflective properties. This research marks a milestone in understanding the survival of planets in extreme environments beyond our Solar System.
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