Lower those finger horns. "Iron Winds and Metal Rain" may be an awesome title for an album by a heavy metal band, but it's also a fairly accurate weather prediction for a hellish exoplanet called WASP-76b. The discovery of iron winds on this world demonstrate just how truly "alien" some planets beyond our solar system are.
Located around 634 light-years away from Earth in the Pisces constellation, the strange and hostile extrasolar planet or "exoplanet" has temperatures of around 4,350 degrees Fahrenheit (2,400 degrees Celsius), hot enough to vaporize iron and cause iron rains to pummel the planet's surface.
These intimidating temperatures arise from WASP-76b's proximity to its star, which classifies it as a "hot Jupiter" planet. This proximity also causes the planet to be tidally locked to its star, meaning one side always faces its sun, blasting it with radiation in perpetuity.
Recently, a team of scientists from the University of Geneva (UNIGE) and the PlanetS National Centre of Competence in Research (NCCR PlanetS) has discovered the presence of high-speed winds carrying vaporized iron from the permanent "dayside" of the planet to its relatively cooler "nightside," which perpetually faces out into space.
Once at the nightside of WASP-76b, the iron condenses and falls as molten metal droplets due to the cooler temperatures on the planet's permanent dark side.
"This is the first time that such detailed optical observations have been made on the day side of this exoplanet, providing key data on its atmospheric structure," research lead author Ana Rita Costa Silva, a doctoral student at the Instituto de Astrofísica e Ciências do Espaço said in a statement. "Our observations indicate the presence of powerful iron winds, probably fueled by a hot spot in the atmosphere."
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None more metal than WASP-76b
Silva and colleagues reached their conclusion by observing light from the dayside of the planet using the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) instrument mounted on the Very Large Telescope (VLT).
ESPRESSO is noted for both its precision and stability, allowing the team to collect high-resolution spectra of WASP-76b. These spectra revealed the signature of iron atoms moving through the hot Jupiter's atmosphere. This technique, called "high-resolution emission spectroscopy," has already proven itself a powerful tool for the study of exoplanet atmospheres.
"ESPRESSO’s ability to make such precise measurements is crucial," team member Christophe Lovis, UNIGE astronomer and member of the NCCR PlanetS crew, explained. "This level of precision allows us to explore the dynamic processes in the atmospheres of exoplanets like WASP-76 b with an unprecedented level of detail."
Since WASP-76b was first discovered in 2013, it has been at the forefront of exoplanet investigation. It is never far from the headlines and continues to boggle the mind with its violent conditions, which have made some of us grateful to live in a comparatively subdued solar system.
For instance, just this April, researchers observed a rainbow-like effect called "glory" in the atmosphere of the violent planet. This represented the first time glory, a rainbow-like arrangement of colorful, concentric rings of light that occur only under peculiar conditions, had been seen outside the solar system.
This finding and the new discovery of iron winds demonstrate how complex the atmospheres of exoplanets can be. The new discovery of iron winds, in particular, could assist scientists in building 3D models of this exoplanet's climate, which could one day help them predict similar phenomena occurring on other hot Jupiter planets and over different types of exoplanets.
"The work on WASP-76 b shows us just how extreme atmospheric conditions can be on ultra-hot Jupiters," discovery team member David Ehrenreich, a researcher and member of the NCCR PlanetS team, concluded. "In-depth analysis of this type of planet provides us with valuable information for a better understanding of planetary climates as a whole."
The team's research is published in the journal Astronomy & Astrophysics.
