Astronomers have detected an unexpected chemical high in the atmospheres of two scorching exoplanets, where liquid iron and gemstones rain down from the skies.
The two exoplanets, which orbit separate stars beyond our solar system, are ultra-hot gas giants called WASP-76b and WASP-121b. Astronomers used the European Southern Observatory’s Very Large Telescope to detect barium at high altitudes in the atmosphere of each exoplanet.
Barium is the heaviest element ever discovered in an exoplanet’s atmosphere. The journal Astronomy & Astrophysics published a study detailing the discovery on Thursday (13).
With each revelation, WASP-76b and WASP-121b look stranger to scientists.
“The intriguing and counterintuitive part is, why is there such a heavy element in the upper layers of the atmosphere of these planets?” the study’s lead author, Tomás Azevedo Silva, a doctoral student at the University of Porto and the Institute of Astrophysics and Space Sciences in Portugal, said in a statement.
“This was in a way an ‘accidental’ discovery. We weren’t expecting or looking for barium in particular and had to verify that this really came from the planet as it had never been seen on any exoplanets before.”
Both exoplanets are similar in size to Jupiter, the largest planet in our solar system, but have incredibly hot surface temperatures well above 1,000 degrees Celsius.
The rising temperatures on WASP-76b and WASP-121b stem from the fact that each planet is located close to its host star, completing a single orbit in about a day or two.
First discovered in 2015, WASP-121b is about 855 light-years from Earth. The exoplanet has a glowing water vapor atmosphere, and the intense gravitational pull of the star’s orbits is warping it into the shape of a football.
The planet is tidally locked, which means that the same side of the planet is always facing the star. This is similar to how our moon orbits Earth. On the day side, temperatures start at 2227ºC in the deepest layer of the atmosphere and reach 3227ºC in the upper layer.
Scientists first spotted WASP-76b in 2016. It orbits a star in the constellation Pisces 640 light-years from Earth. This exoplanet is also tidally locked, so on its star-facing dayside, temperatures exceed 2,426°C.
The scorching nature of exoplanets has given them unusual characteristics and weather that look like something straight out of science fiction. Scientists think that liquid iron rains down from the sky on WASP-76b, while clouds of metal and liquid gems form on WASP-121b.
The detection of barium in each planet’s upper atmosphere surprised researchers. The element is two and a half times heavier than iron.
“Given the high gravity of the planets, we would expect heavy elements like barium to rapidly fall into the lower layers of the atmosphere,” said study co-author Olivier Demangeon, a postdoctoral researcher at the University of Porto and the Instituto de Astrofísica and Space Sciences in Portugal, in a statement.
Finding barium in the atmospheres of both exoplanets could suggest that the ultra-hot gas giants have even more unusual characteristics than previously suspected.
On Earth, barium appears in the night skies as a vibrant green color when fireworks go off. But scientists aren’t sure what natural process is causing the heavy element to appear so high in the atmosphere of these gas giants.
The research team used the ESPRESSO instrument (Echelle Spectrograph for Rocky Exoplanets and Stable Spectroscopic Observations), installed on the Very Large Telescope in Chile, to study starlight as it passed through each planet’s atmosphere.
“Being gaseous and hot, their atmospheres are very extensive,” Demangeon said, “and so are easier to observe and study than those of smaller or cooler planets.”
Future telescopes will also be able to spy more detail within the atmospheric layers of exoplanets, including rocky Earth-like ones, to unravel the mysteries of unusual worlds across the galaxy.
Source: CNN Brasil
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