Scientists find extreme exoplanet raining with iron

Katie Ramirez
March 13, 2020

This study was done in 60 days of WASP-76b by the European Southern Observatory's Very Large Telescope located in Chile.

The incessant exposure to the star's heat keeps WASP-76b's "day side" constantly roasting at about 4,350 degrees Fahrenheit (2,400 degrees Celsius)-hot enough to vaporize metals-while its other face remains perpetually plunged into darkness, staying a whopping 1,600 degrees Fahrenheit cooler. There, drastically cooler temperatures let the iron condense into drops and fall as a odd rain.

According to the University of Geneva professor David Ehrenreich, it is likely that it rains every night at the exoplanet, except it rains iron rather than water.

The Swiss researcher and colleagues have just published their findings on this odd place in the journal Nature.

WASP-76b is tidally-locked, only ever showing one side to its parent star, WASP-76, much the same way the moon only ever shows on face to the Earth.

"Exoplanet" is the name given to a planet outside our own Solar System which orbits around a different star than our Sun. In addition, these winds also bring a pair of iron, which are thus literally turn to the dark side (Darth Vader would be appreciated).

"The observations show that iron vapour is abundant in the atmosphere of the hot day side of WASP-76b", said María Rosa Zapatero Osorio, another co-author of the study from the Centre for Astrobiology in Spain.

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"Surprisingly, however, we do not see the iron vapor in the morning. In other words, it rains iron on the night side of this extreme exoplanet", explained Christophe Lovis from the University of Geneva. Despite being colder on the night side of the planet, temperatures are still scorching and hovering around 1,500 degrees Celsius, meaning the liquid metal falling from the sky would be very uncomfortable. Scientists have discovered that the local weather conditions include 2,400C temperatures, winds in excess of 10,000mph and a steady pelting of iron rain.

Using the new Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations (ESPRESSO) instrument on ESO's VLT in the Chilean Atacama Desert, the astronomers identified for the first time chemical variations on an ultra-hot gas giant planet.

The researchers also observed iron vapor present in the atmosphere at the border of the evening time and day time of WASP-76b.

"The extreme atmospheric conditions met in WASP-76b and its siblings, other "ultra-hot" gas giants, are not found anywhere in our solar system and would be very hard to reproduce in a lab".

The team who studied the phenomenon with the help of Espresso discovered that iron rain starts from day to night starts at an interesting coined line called the "terminator". But on exoplanet WASP-76b, cats and dogs does not come close to describing its metallic precipitation. Astronomers originally planned to use this VLT instrument to study Earth-like planets around stars like our sun.

"What we have now is a whole new way to trace the climate of the most extreme exoplanets", concludes Ehrenreich.

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