It could be raining molten iron.
The Very Large Telescope in Chile has detected more about a distant planet than I ever expected was possible.
Wasp-76b orbits it’s star at 3% of the distance that Earth orbits from the Sun, which accounts for a temperature to vaporize iron. At this distance, a planet, even the gas giant this seems to be, would be tidally locked, with one face always exposed to its star’s radiation.
The extreme temperature difference between the day and night sides produces ferocious winds that carry the iron vapour to the cooler night side, where temperatures decrease to about 1,500C and the iron condenses and falls as rain that constantly peppers the planet’s gas surface and vanishes beneath it. The Guardian reporting on a study published in Nature
Using the Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations, astronomers watch for a dip in starlight that can indicate a planet is crossing in front of the star. Okay, that’s become a standard, accepted method.
Scientists have now moved on to more refined observations that look not only at the dip in intensity but how the spectrum of the light is shifted, which can reveal what gases are present in the planet’s atmosphere.
BTW, it probably isn’t exactly raining iron. It’s unlikely that large droplets form, since temperatures could be higher in the lower atmosphere, even on the planet’s night side. Maybe…iron fog.