How can barium be found on another planet when even stars cannot produce elements heavier than Iron?
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Using the European Southern Observatory’s (ESO) Very Large Telescope (VLT), astronomers discovered barium, the heaviest element ever discovered in an exoplanet’s atmosphere. They were surprised to discover high-altitude barium in the atmospheres of the ultra-hot gas giants WASP-76 b and WASP-121 b, two exoplanets and planets orbiting stars outside our solar system. This unexpected discovery raises questions about what these exotic ambiences might look like.
“The confusing and counterintuitive part is why there are such heavy elements in the upper atmospheres of these planets.” He led a study published today in Astronomy & Astrophysics.
WASP-76 b and WASP-121 b are not normal exoplanets. Both are known as super-hot Jupiters because they are similar in size to Jupiter, but their surface temperatures exceed 1000°C. This is due to its proximity to its main star. This also means that an orbit around each star only takes her a day or two. This gives these planets a rather exotic character. For example, on WASP-76 b, astronomers think it’s raining iron.
Still, scientists were surprised to find barium 2.5 times heavier than iron in the upper atmosphere of WASP-76 b and her WASP-121 b. “Given the planet’s high gravity, we would expect heavy elements like barium to fall rapidly into the lower layers of the atmosphere,” explains co-author Olivier Desmangeon, a researcher at the University of Porto and IA. “It was a kind of ‘accidental’ discovery,” says Azevedo Silva. “We weren’t expecting or looking for barium specifically. It hadn’t been seen on an exoplanet before, so we had to make sure this was indeed from a planet.” .”
The fact that barium was detected in the atmospheres of these two super-hot Jupiters suggests that this category of planets may be even stranger than previously thought. We sometimes see barium in our skies as the bright green color of fireworks, but scientists are wondering what causes this heavy element to exist at such high altitudes on these exoplanets. I’m wondering if it’s a natural process. “At the moment we don’t know what the mechanism is,” he explains Demangeon.
Super hot Jupiter is very useful when studying the atmospheres of exoplanets. As Demangeon explains, “Because their atmospheres are gaseous and hot, they are so extensive that they are easier to observe and study than smaller or cooler planets.”
Determining the composition of exoplanet atmospheres requires very specialized instruments. The team used his ESPRESSO instrument at ESO’s VLT in Chile to analyze starlight filtered through the atmospheres of WASP-76 b and WASP-121 b. This allowed us to clearly identify several elements, including barium.
These new results show that we are just scratching the surface of the exoplanet mystery. Using future instruments, such as the high-resolution ArmazoNes High Dispersion Echelle Spectrometer (ANDES) operating on ESO’s upcoming Extremely Large Telescope (ELT), astronomers will be able to explore large and small planets, including the atmospheres of similar rocky planets. It will be possible to study the atmospheres of exoplanets. Reach deeper into Earth to gather more clues about the nature of these alien worlds.
The study was published in the article “Detection of barium around the super hot gas giants WASP-76b & WASP-121b,” published in Astronomy & Astrophysics.
More information: T. Azevedo Silva et al, Detection of barium in the atmospheres of the ultra-hot gas giants WASP-76b and WASP-121b, Astronomy & Astrophysics (2022). DOI: 10.1051/0004-6361/202244489