It has been announced that on the exoplanet known as Wasp-76b it probably rains iron.
The discovery, published in the journal Nature, was made using ESO’s Very Large Telescope (VLT). A new instrument on this telescope, named ESPRESSO (Echelle SPectograph for Rocky Exoplanets and Stable Spectroscopic Observations) enabled scientists to observe chemical variations on this ultra-hot gas giant for the first time.
David Ehrenreich of the University of Geneva who led the study, explained: “One could say that this planet gets rainy in the evening, except it rains iron.” When strong winds transport iron vapour from the exoplanet’s light or day side, which is hot enough to vaporise metals, to the night side, the 1,000 degree drop in temperature enables the vapour to condense into iron droplets, hence the iron rain. It is for this reason “we do not see the iron vapour in the morning” Ehrenreich explains, because “it is raining iron on the night side of this extreme exoplanet.”
The exoplanet is located 640 light-years from Earth, and like the Moon to the Earth, it only shows one face to its parent star throughout its orbit, always leaving a cooler dark night side. The day side, however, receives thousands of times more radiation from its parent star in comparison to the radiation the Earth receives from the sun.
These findings come from the very first use of ESPRESSO for scientific observations, and as Ehrenreich points out, his team has provided “a whole new way to trace the climate of the most extreme exoplanets.”