Astronomers utilizing the NASA/ESA/CSA James Webb Space Telescope have made a significant breakthrough by detecting silicon monoxide in the atmosphere of the ultrahot Jupiter WASP-121b.
This marks the first time this molecule has been definitively identified in any planetary atmosphere, including those in our own Solar System and beyond.
The groundbreaking findings, published in Nature Astronomy, provide a new understanding of the complex atmospheric dynamics and chemical processes that govern the formation of planets.
WASP-121b is an extraordinary exoplanet, measuring approximately 1.87 times larger than Jupiter and 1.18 times more massive.
It orbits an F6-type star about 881 light-years away, situated in the constellation Puppis.
The planet’s remarkably close orbit around its star enables it to complete a full revolution in just 1.3 days, exposing it to intense stellar radiation and gravitational forces.
As a result, the temperature on its dayside reaches more than 3,000 degrees Celsius, while the nightside cools down to around 1,500 degrees Celsius.
These extreme temperature variations create conditions under which traditional atmospheric chemistry breaks down, allowing for the presence of unusual gaseous molecules like silicon monoxide.
Dr. Thomas Evans-Soma from the University of Newcastle elaborated on this phenomenon, stating that the high dayside temperatures permit refractory materials, which are normally solid, to transform into gaseous components of the atmosphere.
Consequently, minerals that would typically remain solid at lower temperatures vaporize, contributing to the distinctive atmospheric composition of WASP-121b.
The detection of silicon monoxide (SiO) is a landmark achievement in the field of exoplanetary science.
Dr. Anjali Piette from the University of Birmingham highlighted the significance of this discovery, noting that it represents the first conclusive identification of silicon monoxide within any planetary atmosphere.
This finding offers a new perspective on exoplanet atmospheres by showcasing the existence of refractory molecules that can enlighten scientists about chemical processes occurring under extreme conditions.
Moreover, the presence of silicon monoxide, along with water and carbon monoxide, on the planet’s dayside illustrates a sophisticated atmospheric chemistry influenced by both high temperatures and intense radiation.
To unravel the planet’s atmospheric characteristics, researchers employed a technique known as phase curve observation.
This method measures changes in the planet’s brightness during its orbit, allowing astronomers to discern the chemical variations between its two hemispheres.
In an unexpected twist, the study revealed the presence of methane on the cooler nightside of WASP-121b, a finding that surprised researchers since methane typically degrades at high temperatures.
Dr. Piette expressed astonishment, stating, “Given how hot this planet is, we weren’t expecting to see methane on its nightside.”
This suggests that complex atmospheric circulation and chemistry may be at play on the planet.
The chemical composition observed on the nightside indicates a dynamic process known as vertical mixing, where gases are transported from deeper atmospheric layers to the observable infrared photosphere.
Dr. Piette further explained that this vertical mixing likely plays a pivotal role in maintaining the survival of methane and other molecules in localized pockets, despite the planet’s overall extreme environment.
The findings from WASP-121b not only enhance our knowledge of exoplanet atmospheres but may also pave the way for future exploration into the chemical intricacies of distant worlds.
image source from：https://dailygalaxy.com/2025/06/james-webb-molecule-exoplanet/
