Astronomers have discovered the heaviest element ever found in an exoplanet’s barium atmosphere. They were surprised to find barium at high altitudes in the atmospheres of the superheated gas giants WASP-76 b and WASP-121 b, two exoplanets, planets orbiting stars outside our solar system. This unexpected discovery raises questions about the shape of this strange atmosphere.
“The confusing and counterintuitive part is: why are there such heavy elements in the upper atmospheres of these planets?” said Tomas Azevedo Silva, a doctoral student at the University of Porto and the Instituto Astrofísica e Ciencias do Espaco (IA) in Portugal, who led the research published today in Astronomy and Astrophysics.
WASP-76 b and WASP-121 b are not ordinary exoplanets. Both are known as very hot Jupiter because they are comparable in size to Jupiter while their surface temperatures are very high, exceeding 1,000 degrees Celsius. This is due to its proximity to its parent star, which also means it only takes a day or two to orbit each star. This gives these planets a rather strange feature; On WASP-76 b, for example, astronomers thought it rained iron.
However, the scientists were surprised to find barium, which is 2.5 times heavier than iron, in the upper atmosphere of WASP-76b and WASP-121b. “Due to the high gravity of the planets, we expect heavy elements such as barium to quickly fall into the lower atmosphere,” explains co-author Olivier Demangeon, also a researcher at the Universities of Porto and IA.
“This is a ‘coincidence’ discovery,” said Azevedo Silva. “We weren’t expecting or looking for barium in particular and had to check if it really came from this planet as it hadn’t been seen on any exoplanet before.”
The fact that barium was detected in Jupiter’s extremely hot second atmosphere suggests that this class of planets may be more exotic than previously thought. Although we sometimes see barium in our skies, as a bright green color in fireworks, the question for scientists is what natural process could have caused this heavy element at such high altitudes on this exoplanet. “Right now, we’re not sure what the mechanism is,” Demanjohn explains.
In studying the atmospheres of exoplanets, very hot Jupiter is very useful. As Demangon explains: “Due to the gas and heat, the atmosphere is very elongated and therefore easier to observe and study than smaller or colder planets.”
Determining the composition of an exoplanet’s atmosphere requires highly specialized equipment. The team used the ESPRESSO instrument at ESO’s VLT in Chile to analyze starlight filtered through the atmospheres of WASP-76b and WASP-121b. This made it possible to clearly detect some of the elements contained in it, including barium.
These new findings suggest that we are only undermining the secrets of the exoplanets. With future instruments such as the ArmazoNes High Resolution High Dispersion Echelle Spectrograph (ANDES), which will operate on ESO’s upcoming Very Large Telescope (ELT), astronomers will be able to study the atmospheres of large and small exoplanets, including rocky planets. in Earth style. , deep. bigger and to collect more clues about the nature of this alien world.
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