Scientists think they have discovered an ultra-hot giant exoplanet with permanently day and night-sides where it rains iron. What is the name of this planet? Exoplanet WASP-76b.
This exoplanet is 640 light-years away in the constellation of Pisces. It orbits its star every 1.8 days from 0.03 AU, which is 0.03 times as far as Earth is from the sun. First identified in 2013, it’s pretty close to its host star and both orbit in a short period of time with a high surface temperature. All of this combined makes it non-habitable.
WASP-76b rains iron because it’s tidally locked to its host star. This means that it only shows one side, like the moon, does to Earth. The length of time is the same to rotate on its axis and go around the star. During the day, temperatures can reach 2,400 º C/4,352 º F. These temperatures are high enough to evaporate metals, creating the iron vapor. Once it reaches nighttime, temperatures drop to 1,000 º C/1,800 º F. This drop creates strong winds that carry the iron vapor from day to night. When it gets cooler, the iron vapor condenses into iron droplets, creating the rain.
David Ehrenreich, a professor in the Department of Astronomy at the Universite de Geneve said, “one could say this planet gets rainy in the evening, except it rains iron. The conclusion is that the iron has condensed during the night.”
The significance in all of this is that it’s the first time chemical variations have been identified on an ultra-hot gas giant planet. Using advanced equipment in the Chilean Atacama Desert, astronomers were able to detect iron vapor at the evening border of the planet, separating from its night side. A major discovery is that it only rains on the nightside of this exoplanet. All this data was gathered with a new instrument called Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) in September 2018. The significance lies with scientists being able to trace the climate on extreme exoplanets.