Scientists discover planet where it rains iron

Madrid. A team of Spanish and Swiss scientists has discovered a giant exoplanet with daytime temperatures capable of vaporizing iron, and that could condense into raindrops in the night regions.

This is WASP-76b, located about 640 light years away in the constellation of Pisces whose discovery has been made possible by the new ESPRESSO instrument installed in the Very Large Telescope (VLT, very large telescope) telescope of the European Southern Observatory (ESO) ), on Cerro Paranal in the Chilean Atacama desert.

It is an extremely hot giant exoplanet, with daytime temperatures rising above 2,400 degrees, high enough to vaporize metals such as iron.

And strong winds carry iron vapor into cooler night regions, with temperatures dropping to around 1,500 degrees, condensing the vapor into droplets that could precipitate as rain.

“It could be said that this planet becomes rainy at night, with the exception that it rains iron,” summarizes David Ehrenreich, researcher at the University of Geneva and lead author of the study published in the journal Nature.

In addition to scientists from the University of Geneva, researchers from the Canary Islands Institute of Astrophysics and the Center for Astrobiology (CAB, joint center of the Higher Council for Scientific Research -CSIC- and the National Institute of Aerospace Technology) sign the work.

According to the ESO, CAB and CSIC notes, WASP-76b not only shows notable differences in temperature between the day and night faces, but also has a different chemistry in both regions.

Using the new ESPRESSO instrument, researchers have identified chemical variations for the first time on a giant exoplanet and detected “the unequivocal signature” of the presence of iron vapor in the terminator zone, the border of the planet where the day is spent. at night.

This “curious atmospheric phenomenon” occurs because the planet always shows the same face to its host star, causing its other, colder side to be plunged into perpetual darkness.

Like the Moon in its orbit around Earth, this exoplanet takes the same time to rotate on its axis as it goes around its star.

The WASP-76b exoplanet receives thousands of times more radiation from its host star than the Earth of the Sun, which causes the temperature in its daytime face to be so high that the molecules separate into atoms, and that metals such as iron are found in the atmosphere in the form of steam.

The huge temperature difference between the day and night faces (more than 1,000 degrees) would be the cause of the strong winds.

CAB researcher María Rosa Zapatero, who coordinates the ESPRESSO scientific team, explains that “observations show that iron vapor is abundant in the atmosphere of the hot and daytime face of WASP-76b. Part of that iron is injected into the dark side of the planet due to its rotation and atmospheric winds; there, he comes across a vastly cooler environment, condenses and rushes. “

ESPRESSO was originally designed to “hunt” Earth-like planets in orbit around stars like the Sun, but it has turned out to be a much more versatile instrument.

“We soon realized the potential of the VLT, which, together with the great stability of ESPRESSO, make this telescope a fundamental tool for studying the atmospheres of exoplanets,” says Pedro Figueira of ESO.

For Ehrenreich, “the work also shows that we have a new way to track the climate of the most extreme exoplanets.”

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