Astronomers detected the heaviest element yet in two exotic exoplanets

And it rains liquid iron and gems on these exoplanets.
Ayesha Gulzar
Artist’s impression of an ultra-hot Jupiter transiting its star.
Artist’s impression of an ultra-hot Jupiter transiting its star.

ESO/M. Kornmesser 

Astronomers have discovered the heaviest element yet within the atmosphere of two blisteringly hot exoplanets where it rains liquid iron and gems from the skies. As if that was not enough, researchers have now detected barium in their upper atmosphere, making them even more unusual than previously thought.

"This was, in a way, an 'accidental' discovery. 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," said lead study author Tomás Azevedo Silva, a doctoral student at the University of Porto and the Institute of Astrophysics and Space Sciences in Portugal, in a statement.

Exotic Exoplanets

The two exoplanets, WASP-76 b and WASP-121 b, orbit stars outside our Solar System. They are categorized as ultra-hot Jupiter as they are similar in size to Jupiter, the largest planet in our solar system. But these exoplanets have incredibly hot surface temperatures well above 1,832 degrees Fahrenheit (1,000 degrees Celsius). The soaring temperatures on these exoplanets stem from the fact that each planet is located close to its host star, completing a single orbit in about one or two days.

The sizzling temperature of the exoplanets gives these worlds their unusual characteristics, like how WASP-76 b is thought to experience showers of iron from the sky, while WASP-121b experience metal clouds and flurries of gems.

A surprising Discovery

Astronomers were surprised to find barium in the upper atmosphere of these exoplanets. The element is 2.5 times heavier than iron.

"The puzzling and counterintuitive part is: why is there such a heavy element in the upper layers of the atmosphere of these planets?" said Tomás Azevedo Silva

"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 study coauthor Olivier Demangeon, a postdoctoral researcher at the University of Porto and the Institute of Astrophysics and Space Sciences in Portugal, in a statement.

While researchers are not sure about the mechanism yet, the discovery suggests that the atmosphere of such exoplanets could be far more exotic than previously thought.

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"Being gaseous and hot, their atmospheres are very extended," Demangeon said, "and are thus easier to observe and study than those of smaller or cooler planets."

The team used an instrument on European Southern Observatory's Very Large Telescope (ESO's VLT) named Espresso, which analyzes starlight passing through an exoplanet's atmosphere. Based on the properties of the starlight, it's possible to reverse-calculate what kind of atmosphere it had to pass through before reaching the analyzer and decode what elements live in that atmosphere, including barium.

These new results show that we have only scratched the surface of the mysteries of exoplanets. With future instruments such as the high-resolution ArmazoNes high Dispersion Echelle Spectrograph (ANDES), which will operate on ESO's upcoming Extremely Large Telescope (ELT), astronomers will be able to study the atmospheres of exoplanets large and small, including those of rocky planets similar to Earth, in much greater depth and to gather more clues as to the nature of these strange worlds.

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