Things might seem apocalyptic here on Earth right now, but out in the constellation of Pisces is a planet that is the very image of hell: Surface temperatures of over 2400 degrees Celsius (4352 degrees Fahrenheit) are high enough to vaporize metals, so on this planet, it rains iron.
The planet, called WASP-76b, was located using the European Southern Observatory’s Very Large Telescope (VLT). Its extreme environment arises because it is tidally locked, meaning one side of the planet always faces its sun, so it gets extremely hot on the daylight side and is much cooler on the night side which is perpetually dark.
This illustration shows a nightside view of the exoplanet WASP-76b. The ultra-hot giant exoplanet has a dayside where temperatures climb above 2400 degrees Celsius, high enough to vaporize metals. Strong winds carry iron vapor to the cooler night side where it condenses into iron droplets. To the left of the image, we see the evening border of the exoplanet, where it transitions from day into night. ESO/M. Kornmesser
The heat on the dayside is so intense that it rips apart molecules and causes metals like iron to convert to vapor, which rises into the atmosphere before cooling when it arrives on the night side and falling from the sky in droplets like rain.
“The observations show that iron vapor is abundant in the atmosphere of the hot dayside of WASP-76b,” María Rosa Zapatero Osorio, an astrophysicist at the Centre for Astrobiology in Madrid, Spain, explained in a statement. “A fraction of this iron is injected into the nightside owing to the planet’s rotation and atmospheric winds. There, the iron encounters much cooler environments, condenses and rains down.”
This comic-book-style illustration by Swiss graphic novelist Frederik Peeters shows a close-up view of the evening border of the exoplanet WASP-76b. The ultra-hot giant exoplanet has a dayside where temperatures climb above 2400 degrees Celsius, high enough to vaporize metals. Strong winds carry iron vapor to the cooler night side where it condenses into iron droplets. Theoretical studies show that a planet, like WASP-76b, with an extremely hot day side and colder night side would have a gigantic condensation front in the form of a cloud cascade at its evening border, the transition from day to night, as depicted here. Frederik Peeters
The information about this planet was collected using the VLT’s new ESPRESSO, or Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations, instrument. This instrument can detect tiny shifts in the gravity of star systems caused by the presence of exoplanets. “We soon realized that the remarkable collecting power of the VLT and the extreme stability of ESPRESSO made it a prime machine to study exoplanet atmospheres,” says Pedro Figueira, ESPRESSO instrument scientist at ESO in Chile.
“What we have now is a whole new way to trace the climate of the most extreme exoplanets,” Ehrenreich said.