In our Solar System, the brightest planet of all is Venus: its proximity to the Sun and its atmosphere mean that it has a very high reflectivity, equal to approximately 75%.
However, there is one planet, discovered in 2020, that exceeds this value: it is called LTT 9779 b and is known as the “mirror” planet due to its incredible brightness.
It is located about 260 light years away from us and is a “hot Neptune”, with a mass similar to Neptune but much closer to its star, completing an orbit in less than a day. Its proximity to the star makes it extremely hot, with temperatures exceeding 1,700 degrees Celsius.
But the most fascinating thing about this exotic world is its atmosphere rich in metals and silicates, which reflects about 80% of the light it receives. This makes it one of the most reflective exoplanets ever discovered.
And for us, it is a natural laboratory for studying exoplanetary atmospheres: how does a planet manage to maintain an atmosphere in such extreme conditions?
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