It rains iron every night on this planet

Hyperaxion March 11, 2020 6:45 pm

Astronomers have found that on exoplanet WASP-76b, 390 light-years from Earth, temperatures reach 2400ºC – hot enough to make some metals evaporate.

A team from the European Organization for Astronomical Research in the Southern Hemisphere (ESO) discovered a peculiar exoplanet in the Pisces constellation, 390 light-years from Earth: it rains iron every night there. The discovery of the WASP-76b, as it was named, occurred thanks to the Very Large Telescope (VLT), located in the Atacama Desert, in Chile.

In an article about the discovery to be published in the journal Nature, scientists explain that this event occurs because only one side of the planet is facing its star, which indicates that it is “stuck” – taking a long time to rotate around its axis.

Representation of the exoplanet WASP-76b around its local star.
Representation of the exoplanet WASP-76b around its local star. (Credit: European Southern Observatory).

This means that on one side of the WASP-76b it is always day and, on the other, it is always night, as it happens with the Moon. The illuminated face receives thousands of times more radiation from its parent star, than the Earth receives from the Sun, for example, and this causes the temperatures there to exceed 2400ºC, resulting in the evaporation of various substances, including iron.

Read more: New technique allows astronomers to study “baby” exoplanets

However, the metal does not remain in its gaseous form: due to the temperature difference between the faces of the planet, strong winds are generated and clouds charged with the substances are taken to the dark side of the WASP-76b. There, the temperature is 1500ºC, which causes this ultra-hot cloud to condense, resulting in rain.

Strong winds are generated and clouds charged with iron are taken to the dark side of the WASP-76b, resulting in rain.
Strong winds are generated and clouds charged with iron are taken to the dark side of the WASP-76b, resulting in rain. (Credit: ESO/M. Kornmesser).

“Observations show that iron vapor is abundant in the atmosphere on the day side of WASP-76b,” said María Rosa Zapatero Osorio, one of the researchers, in a statement. “A fraction of this iron is ‘injected’ into the night side due to the planet’s rotation and atmospheric winds. There, the iron finds much colder environments, condenses and rains.”

According to astronomers, the discovery was only possible thanks to ESPRESSO, a VLT instrument that helps experts monitor the atmosphere of exoplanets. “What we have now is a whole new way of tracking the climate of the most extreme exoplanets,” said David Ehrenreich, the study’s leader.

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