You’d think with how distant the planets Jupiter and Saturn are from the Sun compared to, say, Earth and Venus, that gas giants like them tend to stay away from their host stars. However, given the roughly 5,000 exoplanets we’ve seen so far, about 300 of them are expected to be “hot Jupiters,” or gas giants that orbit extremely close to their host stars—and the distant exoplanet WASP-189b may have more to its scorching-hot atmosphere than meets the eye.
This particular exoplanet sits at about 322 light-years away—not exactly a day trip—as it orbits its host star WASP-189. What’s closer to a day trip, though, is its year; it’s so close to its star, despite being roughly 1.6 times Jupiter’s size, that a year on WASP-189b takes just a little bit less than 3 Earth days.
Now, first author and Lund University (LU) doctoral student Bibiana Prinoth, together with a team of scientists, started to peer their space eyes into this bizarre gas giant and managed to map its atmosphere. What they found, surprisingly enough, is a giant planet that may have a layered atmosphere. The remarkable findings by Prinoth and the team were published in the journal Nature Astronomy.
“In the past, astronomers often assumed that the atmospheres of exoplanets exist as a uniform layer and try to understand it as such,” said LU astronomer Jens Hoeijmakers. “But our results demonstrate that even the atmospheres of intensely irradiated giant gas planets have complex three-dimensional structures.”
Astronomers like Hoejimakers and Prinoth find information about distant planets’ atmospheres through the use of starlight coming from its own host star. You see, different compounds absorb light as it passes over their molecules in different but distinct ways. This means that scanning and looking through these light “patterns” can reveal the chemical makeup of gas giants like WASP-189b as light from its host star passes over it on its way to Earth.
Said Prinoth: “We used a high-resolution spectrograph to collect starlight from the host star, at a time when the light also passed the exoplanet’s gas envelope. After extracting the relevant parts of the spectrum, we were able to link at least nine variants of known substances to the atmosphere of WASP-189b.”
This was when Prinoth, Hoejimakers, and the team found the elements iron (Fe), titanium (Ti), and chromium (Cr) among other metallic elements in its atmosphere—not surprising, considering that WASP-189b’s surface temperatures may reach a blistering 3,200 °C (5,792 °F), which would be certainly enough to melt all but the hardiest of metals.
What’s surprising, however, is the detected presence of titanium oxide (TiO2) in its atmosphere—a world first, according to the team in the Lund University press release. According to the team, TiO2 tends to absorb what is known as “short-wave radiation,” whose examples include ultraviolet (UV).
To the team, this meant that WASP-189b may possess a layer within its atmosphere, whose composition includes gaseous TiO2, that may be interacting with starlight analogous to the function of our own ozone layer.
Prinoth also noted the presence of “alterations” within the absorption lines (graphical data generated from light; the presence of “lines” can show the identity of the elements and compounds present between the light source and the observer) of the starlight that reached Earth and passed over the exoplanet in question. To them, this means that WASP-189b’s atmosphere may be subject to phenomena like strong winds; these processes are known to distort or alter absorption lines.
Prinoth added: “We think that this indicates that they exist in different layers – similarly to how the fingerprints of water vapor and ozone on Earth would appear differently altered from a distance because they mostly occur in different atmospheric layers.”
Prinoth believes that their findings serve as stepping stones into other fields of astronomical research, which now carries more importance than ever given the expanding look into the possibility of life elsewhere in the universe besides our own planet.
References
- Exotic cocktail in the atmosphere of extreme exoplanet. (2022, January 28). Lund University. https://www.lunduniversity.lu.se/article/exotic-cocktail-atmosphere-extreme-exoplanet
- Lendl, M., Csizmadia, Sz., Deline, A., Fossati, L., Kitzmann, D., Heng, K., Hoyer, S., Salmon, S., Benz, W., Broeg, C., Ehrenreich, D., Fortier, A., Queloz, D., Bonfanti, A., Brandeker, A., Collier Cameron, A., Delrez, L., Garcia Muñoz, A., Hooton, M. J., … Wolter, D. (2020). The hot dayside and asymmetric transit of WASP-189 b seen by CHEOPS. Astronomy & Astrophysics, 643, A94. https://doi.org/10.1051/0004-6361/202038677
- Prinoth, B., Hoeijmakers, H. J., Kitzmann, D., Sandvik, E., Seidel, J. V., Lendl, M., Borsato, N. W., Thorsbro, B., Anderson, D. R., Barrado, D., Kravchenko, K., Allart, R., Bourrier, V., Cegla, H. M., Ehrenreich, D., Fisher, C., Lovis, C., Guzmán-Mesa, A., Grimm, S., … Heng, K. (2022). Titanium oxide and chemical inhomogeneity in the atmosphere of the exoplanet WASP-189 b. Nature Astronomy, 1–9. https://doi.org/10.1038/s41550-021-01581-z
- Starr, M. (2022, January 31). The atmosphere of this extreme exoplanet has an intriguing similarity to earth. ScienceAlert. https://www.sciencealert.com/the-atmosphere-of-this-extreme-exoplanet-has-an-intriguing-similarity-to-earth-s
