Just over 5,800 exoplanets – planets that orbit stars other than our Sun – have been discovered since the 1990s. One of the more extreme examples is the ultrahot WASP-121 b, located about 900 light years from Earth. It is somewhat larger than Jupiter, our solar system’s largest planet, and orbits very close to its star. In addition, the planet is in synchronous rotation with the star, just as our Moon’s rotation synchronises with Earth.
This means that one side of the exoplanet always faces the star and is extremely hot, around 2,500 degrees, whereas the other side remains considerably cooler. The temperature difference and how heat moves in such an extreme environment has long been a mystery to researchers. However, in two new studies published in Nature and Astronomy & Astrophysics, research teams, including members from Lund University, have made a number of new observations.
”We discovered that a jet stream transports material around the planet’s equator, while a separate wind further down in the atmosphere transports gas from the hot day side to the cool night side. This climate is unlike anything observed on any planet and poses a challenge to existing theories about atmospheric behavior on extreme worlds.,” says Bibiana Prinoth, an astrophysicist at Lund University
“Vanished” titanium detected
However, this was not the only discovery. Due to the high quality of the new observations, the researchers could for the first time detect titanium in the exoplanet’s atmosphere. Astronomers had previously thought that all titanium had vanished from WASP-121 b, or was present in such small amounts that observation was not possible.
“The discovery challenges our understanding of winds and chemistry on these hot planets and reveals a significant gap between what our current models predict and what we are actually observing on more varied exoplanets,” says Bibiana Prinoth.
Vital knowledge for making new discoveries
Learning more about the diversity of exoplanet atmospheres means that the researchers can better understand how atmospheres work. Through more incisive analysis, the researchers are also laying the foundations for more accurate models, especially as they are now preparing to study Earth-like planets using next-generation telescopes. The appropriately named Extremely Large Telescope is a huge optical telescope with a 39-metre diameter currently being built in Chile by the European Southern Observatory (ESO). The telescope, which will revolutionise our ability to study exoplanets, is expected to start operating before the end of this decade.
”These studies of WASP-121 b are a reminder of how much there is still to explore and discover about the universe. The next generation of telescopes will give us amazing insights into the chemistry and dynamics of distant worlds. We will reveal things that we can only dream about today,” says Bibiana Prinoth.
