Researchers using ESO’s Very Large Telescope have found an ultra-hot gas giant exoplanet where iron rains from the sky at night.
The exoplanet WASP-76 b lies about 640 light-years from the sun, in the constellation Pisces. It circles its host star once every 1.8 Earth days. An orbit so tight that the ultra-hot Jupiter is tidally locked, always showing its parent star the same face.
The local weather conditions, there, include 2,400°C temperatures and winds in excess of 10,000 mph. The temperatures are high enough to vaporize metals.
“These are likely the most extreme climates we could ever find on a planet,” said study lead author David Ehrenreich, an associate professor of astronomy at the University of Geneva in Switzerland.
Meanwhile, strong winds carry iron vapor to the cooler night side where it condenses into clouds, causing rains of liquid iron. This creates the iron they observed in the atmosphere.
Scientists say, this iron rain probably eventually makes its way back to the dayside again via atmospheric circulation, perpetuating the cycle.
“One could say that this planet gets rainy in the evening, except it rains iron,” said prof. Ehrenreich.
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The observations came from the new ESPRESSO instrument on ESO’s VLT. It was originally designed to hunt for Earth-like planets around Sun-like stars.
It does this by observing a star’s small drop in brightness, that occurs as a planet passes across the face of the star.
For giant planets that are very close to their parent star, observing these transits is an easier task as they block out more light.
But astronomers are now using a new observational method. The method looks not only at the dip in intensity but how the spectrum of the light shifts.
This can reveal what gases are present in the planet’s atmosphere.
So far, more than 4,000 exoplanets have been confirmed. So, powerful ground-based observatories that are under construction, such as the Extremely Large Telescope, and the James Webb Space Telescope, which will probably launch next year, may bring astronomers closer to answering whether any of these have the necessary conditions to support extraterrestrial life.