Using the European Southern Observatory's (ESO) Very Large Telescope (VLT), astronomers have found barium, the heaviest element ever detected in the atmosphere of an exoplanet. The discovery of barium in the atmospheres of exoplanets WASP-76 b and WASP-121 b, two extremely hot gas giants orbiting stars outside our solar system, shocked astronomers. This unexpected finding leads to speculation about the potential properties of these strange environments.
The study's lead author and PhD candidate at the University of Porto and the Astrophysics and Space Sciences Institute in Portugal, Tomás Azevedo Silva, said it's a confusing and counterintuitive question why such a heavy element is found in the upper layers of the atmospheres of these planets.
WASP-76 b and WASP-121 b are not typical exoplanets. Both are referred to as "ultra-hot Jupiters." Because they are similar in size to Jupiter and have extraordinarily heated surfaces that rise above 1000°C. This is a result of their proximity to their host star, resulting in an orbital period of one to two days around each star. This gives these planets some unusual properties; For example, in WASP-76 b, astronomers think it rained iron.
However, the discovery of barium, which is 2,5 times heavier than iron, in the upper atmospheres of WASP-76 b and WASP-121 b stunned scientists. According to researcher Olivier Demangeon of the University of Porto and IA, "given the planets' enormous gravity, we would expect heavy elements such as barium to descend rapidly into the lower atmosphere."
According to Azevedo Silva, this discovery was quite accidental. Barium was not something we expected or looked for, so we had to double-check that it was coming from the planet because it had never been observed on an exoplanet before.
The presence of barium in the atmospheres of both of these ultra-hot Jupiters suggests that this class of planets may be even stranger than previously thought. While barium, which gives pyrotechnics its beautiful green color, can occasionally be seen in our own sky, the puzzle for scientists is what natural process could have brought this heavy element to such high levels on these outer planets. Demangeon says: “We are not sure about the mechanisms at this time.
Ultra-hot Jupiters are incredibly helpful in the study of exoplanet atmospheres. Being gaseous and hot, they have an extremely large atmosphere, making them easier to view and study than smaller or cooler planets.
A very special technology is needed to determine the atmosphere of an exoplanet. Using the ESPRESSO instrument at ESO's VLT in Chile, the researchers studied starlight filtering through the atmospheres of WASP-76 b and WASP-121 b. In this way, a number of components, including barium, could be easily identified.
These latest findings show that we are just beginning to unravel the secrets of the outer planets.
Future telescopes such as the European Southern Observatory's (ESO) Extremely Large Telescope (ELT) will be equipped with instruments such as the high-resolution ArmazoNes high-dispersion Echelle Spectrograph (ANDES). This will allow astronomers to study the atmospheres of large and small exoplanets in much greater detail, including rocky Earth-like planets, and to gather more information about the nature of these strange worlds.