Heaviest element ever detected in an exoplanet atmosphere

Using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), astronomers have discovered the heaviest element found in exoplanet atmospheres—barium. They were surprised to discover barium at high altitudes in the atmospheres of the super-hot gas giants WASP-76 b and WASP-121 b—two exoplanets, planets that orbit stars outside our solar system. This unexpected discovery raises questions about what this exoplanet atmosphere might be like.

“The confusing and counterintuitive part is: Why are there so many heavy elements in the upper layers? the atmosphere of these planets?” says Tomás Azevedo Silva, a PhD student at the University of Porto and Portugal’s Instituto de Astrophysica e Ciencias do Espaço (IA) who led the study published today. Astronomy and Astrophysics.

WASP-76 b and WASP-121 b are not typical exoplanets. Both are known as ultra-hot Jupiters because they are comparable in size to Jupiter with surface temperatures well above 1000 degrees Celsius. It is because of them nearby to their host star, meaning that one orbit around each star takes only one to two days. This gives these planets rather exotic features; In WASP-76 b, for example, astronomers doubt it Rain is iron.

But still, scientists were surprised to find barium in the upper atmosphere of WASP-76 b and WASP-121 b, which is 2.5 times heavier than iron. “Because of the high gravity of the planets, we would expect heavy material As barium quickly falls to the lower layers of the atmosphere,” explains co-author Olivier Demenzione, also a researcher at the University of Porto and IA.

“It was an ‘accidental’ discovery in a way,” said Azevedo Silva “We weren’t expecting or specifically looking for barium and had to cross-check that it was actually coming from the planet because it hadn’t been seen on an exoplanet before.”

The detection of barium in the atmospheres of both of these super-hot Jupiters suggests that this class of planets may be even stranger than previously thought. Although we sometimes see barium in our own skies, the bright green color in fireworks, the question for scientists is what natural process could cause this heavy element to be so? high altitude Among these exoplanets. “At this point, we’re not sure what the mechanisms are,” Demenzin explains.

Super-hot Jupiter is extremely useful in the study of exoplanet atmospheres. “Being airy and hot, their atmospheres are very expansive and thus easier to observe and study than smaller or cooler planets,” Demanzione explained.

Determine an essay ExoplanetIts atmosphere requires very special equipment. The team used the ESPRESSO instrument at ESO’s VLT in Chile to analyze starlight filtered through the atmospheres of WASP-76 b and WASP-121 b. This made it possible to identify them clearly with several components Barium.

These new results show that we’ve only scratched the surface of the exoplanet mystery. With future instruments such as the high-resolution Armazones High Dispersion Echel Spectrograph (ANDES), which will operate on ESO’s upcoming Extremely Large Telescope (ELT), astronomers will be able to study the atmospheres of large and small exoplanets, including rocky planets. Similar to Earth, a lot greater depth And to gather more clues about the nature of this strange world.

The research was presented in the paper “Detection of Barium in the Atmospheres of the Superhot Gas Giants WASP-76b and WASP-121b,” which will appear in Astronomy and Astrophysics.