All the planets that make up our solar system orbit around the Sun. Those known as exoplanets are those that orbit around other stars. This is the case of WASP-189b. According to the researchers, it is a gas giant that orbits its star 20 times closer than Earth to the Sun. Astronomers once assumed that the atmospheres of exoplanets were a uniform layer. But new results show that even the atmospheres of intensely irradiated gas giant planets have complex three-dimensional structures.
An extreme exoplanet
Hot Jupiters like WASP-189b are gas giants that orbit close to their star. This produces very high atmospheric temperatures on the day side of the planet, exceeding 3,200 degrees Celsius. A temperature high enough to boil metals like magnesium, iron, or chromium. High temperatures bring these elements into their gaseous state, allowing them to create a layered atmosphere around the planet.
Researchers from the University of Bern, the University of Geneva and Lund University in Sweden discovered the extraordinary chemical composition of WASP-189b’s atmosphere using data from the space telescope Characterizing Exoplanets Satellite (CHEOPS) and the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph at La Silla Observatory in Chile.
“We measure the light coming from the planet’s host star and passing through the planet’s atmosphere. Gases in its atmosphere absorb some of the starlight, similar to ozone which absorbs some of the sunlight in the Earth’s atmosphere, and thus leave their characteristic “fingerprint”. With the help of HARPS, we were able to identify the corresponding substances”, he explains in a release the study’s lead author and doctoral student at Lund University, Bibiana Prinoth.
They find titanium oxide in its atmosphere
According to the researchers, among the metals present in WASP-189b’s atmosphere are iron, chromium, vanadium, magnesium and manganese. One of the interesting substances the team found was a titanium-containing gas: titanium oxide, which is rare on Earth but could play a key role in WASP-189b’s atmosphere. A role very similar to that played by ozone in the Earth’s atmosphere.
“Titanium oxide absorbs short-wavelength radiation, such as ultraviolet radiation,” said study co-author Kevin Heng, a professor of astrophysics at the University of Bern. “Therefore, detecting it could indicate a layer in WASP-189b’s atmosphere that interacts with stellar radiation in a similar way that the ozone layer does on Earth.”
After centuries of observing the planets of our own solar system, a baseline has been developed for what can be considered planet with extreme environments like the carbon dioxide atmosphere of Venus and the runaway greenhouse effect that reaches temperatures of around 482 degrees Celsius. As exoplanets like WASP-189b are observed and analyzed, it becomes more apparent that Venus and Jupiter are just a small sample of how drastic conditions can be on other worlds.
It is clear that planets with metallic atmospheres should not be so surprising given the large amount of iron in the universe. After all, they have a boiling point well below the temperature that most stars can reach. A good way to discover all the mysteries that exoplanets and the universe in general hide is by watching science series, movies or documentaries.