Life as we know it on exoplanet WASP-121 b
The exoplanet WASP-121 b is an extremely harsh environment. This celestial body revolves so closely around a star that is even hotter than our own sun, heating the atmosphere on the planet to nearly 1900 degrees Celsius, or 3452 degrees Fahrenheit. This intense heat combined with the discovery of monumental cyclones, it’s reasonable to describe this alien planet as hellish.
Close encounters
Positioned 880 light-years from Earth, WASP-121 b bears the brunt of a vast UV light wave emanating from its star. This wave causes magnesium and iron gas to leave the planet and rattle off into space. The gravitational pull that the star exerts on WASP-121 b results in the planet being shaped more like a rugby ball rather than a perfect sphere.
Uninhabitable, but informative
Contrary to any illusions, WASP-121 b is incapable of supporting life forms at least as we know them. The driving force behind this research is that it provides essential information on weather patterns on distant planets. This knowledge could eventually lead to the discovery of exoplanets that potentially support life, given their stable climatic conditions.
Gigantic cyclones
Astronomers have made an impressive discovery. Using several years of observations from the Hubble telescope – between 2016 and 2019 – and sophisticated computer models, they found evidence of colossal cyclones thundering across the planet. These cyclones form and are sequentially demolished by the drastic temperature differences between the side of the exoplanet facing the star and the dark side of the planet. On top of this, there are severe storms and a distinguished shift between the hottest area of the planet and the point closest to the star. The chemical composition of the atmosphere also varies significantly.
A rotation every 30 hours
These insights are key to our search for habitable zones beyond our solar system. “Research on exoplanetary weather is crucial for our understanding of the atmospheric complexities of distant worlds, particularly in our pursuit of exoplanets with livable conditions,” says Quentin Changeat from ESA.
WASP-121 b orbits so close to its parent star that a full revolution takes only 30 hours. Due to the star’s proximity, the planet is constantly under the star’s gravitational pull, causing the same hemisphere to always face the star – much similar to how the same side of our moon always faces the Earth.
A crystal-clear image
All these insights are compiled from the multi-year observations documented by the Hubble. “The collected dataset originates from a substantial observing time for a single planet. Currently, it is the only consistent set of such repeated observations,” explains Changeat. “The information derived from these observations is applied to deduce the chemical composition, temperature, and clouds in the atmosphere of WASP-121 b at different instances. This has provided us with an exceptionally clear picture of how the planet changes over time.”
Challenges of exoplanetary observations
Observing planets beyond our solar system is a great challenge. Not only because they are so far away, but also because the stars they orbit are typically a lot larger and brighter than the planets themselves. Astronomers utilising a telescope as powerful as the Hubble still need to combine all of their data to collect enough information to draw reliable conclusions about the characteristics of an exoplanet.
Data archives from the Hubble
Yet this process does not reveal if the planet undergoes changes. In simpler words, they cannot study the weather using this method. To do that, they need much more data collected over a more extended period. Luckily, the Hubble has been active long enough to amass a large data archive, including multiple observation sets from the same exoplanet, such as WASP-121 b.
New Information leading to new knowledge
The recent information about WASP-121 b contributes significantly to our understanding of weather patterns arbitrarily far away. Simultaneously, it aids our hunt for livable planets well beyond our solar system.
