Sci-tech
19:55 12.03.2020(updated 20:23 12.03.2020) Short url
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The wind and heat on the diurnal side of a planet 640 light years from Earth cause the iron in its atmosphere to vaporize, researchers say.
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Thanks to the Very Large Telescope (VLT) of the European Southern Observatory (ESO), astronomers observed a planet where there is iron rain. The results were published in the journal Nature.
The planet WASP-76b in question is about 640 light years from Earth in the constellation Pisces. On the diurnal side of this ultra-hot giant exoplanet, the temperature exceeds 2,400 ° C. A temperature sufficient for the evaporation of metals. A strong wind carries the iron vapors to the colder nocturnal side, where they condense into drops of iron.
“We can say that the evenings are rainy on this planet, except that it is raining iron,” said David Ehrenreich, director of the study of this original exoplanet and professor at the University of Geneva, in the press release from ESO.
Such a strange phenomenon occurs because the iron rain planet is constantly oriented towards its mother star on the diurnal side, while its nocturnal side is plunged into eternal darkness. Just like the Moon, which is connected in the same way to the Earth, the planet WASP-76b is under the influence of the tidal effects of its star.
The diurnal side of the planet is bombarded by radiation from its mother star thousands of times more powerful than Earth by the Sun. It is so hot there that the molecules divide into atoms, and metals such as iron evaporate. The extreme difference in temperatures between the diurnal and nocturnal sides of the planet causes strong winds in the metallic atmosphere which bring ferrous vapors from the warm side towards the colder night side, where the temperature drops to -1,500 ° vs. This is sufficient for the condensation of iron vapor and precipitation in the form of rain.
Ferrous vapor lines
This new study indicates that on the day and night sides of the planet WASP-76b there is a fundamental difference not only in temperatures, but also in terms of chemical composition. Using the new ESPRESSO spectrograph on the ESO VLT telescope in the Chilean mountain desert of Atacama, astronomers have recorded chemical changes on the ultra-hot gas giant for the first time: strong lines of iron vapor on the terminator, the line separating the lighted and unlit faces of a celestial body. The researchers were surprised not to see iron vapors in the “morning” zone of the planet. This is explained, according to them, by the iron rains on the nocturnal side of the planet.
“Observations indicate that the abundance of iron vapor in the atmosphere of WASP-76b is high on the warm lit side of the planet. Part of the iron is brought to the nocturnal side thanks to the axial rotation of the planet and atmospheric winds, “adds one of the authors of the article Maria Rosa Zapatero Osorio, astrophysicist at the Madrid Astrobiological Center, head of the research group -developers of the ESPRESSO spectrograph.
This result was obtained during the very first observations with the ESPRESSO spectrograph in September 2018, carried out by a scientific consortium of specialists from Portugal, Italy, Switzerland and Spain.
A state-of-the-art spectrograph
The Scale Spectrograph for the observation of rocky planets and stable spectroscopic observations (ESPRESSO) was originally designed to search for Earth-like planets around Sun-like stars. But it turned out that the spectrograph could also fulfill other observation functions.
“We quickly understood that the immense collecting power of the VLT and the great stability of ESPRESSO make it a device perfectly suited to the study of exoplanet atmospheres,” said another study author Pedro Figueira from the office. of ESO, responsible for the operation of ESPRESSO.
“Now we have got a whole new method of observing climatic conditions on extraordinary exoplanets,” concludes David Ehrenreich.
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