Astronomers have discovered the heaviest element ever found in an exoplanet atmosphere barium. They were surprised to discover barium at high altitudes in the atmospheres of the ultra-hot gas giants WASP-76 b and WASP-121 b two exoplanets, planets which orbit stars outside our Solar System. This unexpected discovery raises questions about what these exotic atmospheres may be like.
“The puzzling and counterintuitive part is: why is there such a heavy element in the upper layers of the atmosphere of these planets?” says Tomas Azevedo Silva, a PhD student at the University of Porto and the Instituto de Astrofisica e Ciencias do Espaco (IA) in Portugal who led the study published today in Astronomy & Astrophysics. WASP-76 b and WASP-121 b are no ordinary exoplanets. Both are known as ultra-hot Jupiters as they are comparable in size to Jupiter whilst having extremely high surface temperatures soaring above 1000°C. This is due to their close proximity to their host stars, which also means an orbit around each star takes only one to two days. This gives these planets rather exotic features; in WASP-76 b, for example, astronomers suspect it rains iron.
But even so, the scientists were surprised to find barium, which is 2.5 times heavier than iron, in the upper atmospheres of WASP-76 b and WASP-121 b. “Given the high gravity of the planets, we would expect heavy elements like barium to quickly fall into the lower layers of the atmosphere,” explains co-author Olivier Demangeon, a researcher also from the University of Porto and IA
“This was in a way an ‘accidental’ discovery,” says Azevedo Silva. “We were not expecting or looking for barium in particular and had to cross-check that this was actually coming from the planet since it had never been seen in any exoplanet before.”
Barium, the heaviest element ever found in the atmosphere of an exoplanet, has been found by astronomers. They were shocked to find barium in the atmospheres of the exoplanets WASP-76 b and WASP-121 b, two extremely hot gas giants that orbit stars outside of our solar system. This unexpected finding prompts speculation about the potential characteristics of these strange environments
According to Azevedo Silva, this discovery was somewhat accidental. Barium was not something we were expecting or specifically looking for, so we had to double-check that it was coming from the planet because it had never been observed in an exoplanet before.
Both of these ultra-hot Jupiters had barium found in their atmospheres, which suggests that this class of planets may be even stranger than previously believed.
The question for scientists is what natural process could cause this heavy element to be at such high altitudes in these exoplanets, despite the fact that we do occasionally see barium in our own skies as the brilliant green colour in fireworks. Demangeon says, “At the moment, we are unsure of the mechanisms.
Ultra-hot Jupiters are incredibly helpful in the study of exoplanet atmospheres. They have very extended atmospheres due to being gaseous and hot, which makes them easier to observe and study than those of smaller or cooler planets.
These new findings demonstrate that we have only begun to unravel the mysteries of exoplanets. Future telescopes like the Extremely Large Telescope (ELT) of the European Southern Observatory (ESO) will be equipped with instruments like the high-resolution ArmazoNes high Dispersion Echelle Spectrograph (ANDES), which will allow astronomers to study the atmospheres of exoplanets large and small, including those of rocky planets similar to Earth, in much more detail and to glean more information about the nature of these strange worlds.
THEY WEREN’T EXPECTING THAT.
Hell Off-Earth
As exotic as the exoplanets may be, it doesn’t explain what an element as heavy as barium — which is 2.5 times heavier than iron — is doing in their atmospheres.
“Given the high gravity of the planets, we would expect heavy elements like barium to quickly fall into the lower layers of the atmosphere,” said paper co-author Olivier Demangeon, a researcher from the University of Porto and the Institute of Astrophysics and Space Sciences, in the release.
“At the moment, we are not sure what the mechanisms are,” Demangeon conceded.
It’s a stunning discovery, not to mention one that demonstrates how much more we have to learn about these fascinating alien worlds.