Astronomers last March detected a distant planet where iron probably rains.
While this sounds like something out of a science fiction movie, it is the natural state of one of the many extreme worlds we are discovering today.
Called Wasp-76b, this exoplanet orbits so close to its main star that its daytime temperatures exceed 2,400 ° C, hot enough to vaporize metals.
But the night side of this astronomical object is 1,000 degrees cooler, which would allow those metals to condense and rain.
According to Dr. David Ehrenreich of the University of Geneva, it is a rather strange environment.
Imagine that instead of a drizzle of water drops, you have drops of iron splashing“He told the BBC.
The researcher and his colleagues published their findings on this strange place in the scientific journal. Nature.
In their article they describe how the new ESPRESSO, (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations), was used in the Very Large Telescope Project (VLT, literally “very large telescope” in Spanish) of the European Southern Observatory in Chile, to study the Wasp-76b chemistry in detail.
Winds up to 18.000 kilometers per hour
The exoplanet, 640 light years from Earth, is so close to its star that it only takes 43 hours to complete its rotation.
Another interesting feature of this object is that its visible face is always pointing at its star, a behavior that scientists call tidal coupling or synchronous rotation. Earth’s Moon does exactly the same: We only see one side of it.
This means that the permanent daytime side of the Wasp-76b is being roasted steadily.
In fact, this part must be so hot that all the clouds would be scattered and the molecules of its atmosphere divided into individual atoms.
Furthermore, the extreme temperature difference between the illuminated and unlit parts of the exoplanet would generate fierce winds, up to 18.000 kilometers per hour, explains Dr. Ehrenreich’s team.
While using ESPRESSO, scientists detected a strong mark of iron vapor at the Wasp-76b’s night border, or where day gives way to night on that planet.
But when the group observed the transition in the morning, the iron mark disappeared.
“What we assume is that iron condenses on the night side, that, although it is hot (and reaches) 1,400 ° C, is cold enough that iron can condense into clouds, like rain, possibly as drops. These could fall into the deepest layers of the atmosphere that we cannot access with our tools, “says Ehrenreich.
“A hot Jupiter”
Wasp-76b is a giant planet that is twice as wide as Jupiter.
Its unusual name comes from the UK-led Wasp telescope system, which detected this new world four years ago.
Scientist Don Pollacco of the University of Warwick, who is part of the team that discovered him, maintains that he is hard to imagine such exotic worlds.
“This thing orbits so close to its star, it is essentially dancing in that star’s outer atmosphere and is subject to all kinds of physics that, to put it bluntly, we really don’t understand,” he told the BBC.
“Or it will end in the star or the radiation field of the star will blow up the planet’s atmosphere to leave just a hot rocky core. “
Ehrenreich, a fan of graphic novels, asked Swiss illustrator Frederik Peeters to produce an interpretation of Wasp-76b.
“Often with these discoveries, we see detailed 3D compositions for people it is difficult to know if it is a real image or simply from an image made on a computer. Putting some entertainment on this we are not fooling anyone, “he concluded.
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