Astronomers leveraging the NASA/ESA/CSA James Webb Space Telescope have identified water, carbon monoxide, and methane in the atmosphere of WASP-121B, as well as in Earth’s nightside atmosphere. This marks the first detection of silicon monoxide in any planetary atmosphere, including those within our solar system and beyond.
This artistic impression illustrates the phase during which WASP-121B collects most of its gas, inferred from recent findings. Image credit: T. Muller, MPIA & HDA.
WASP-121B is approximately 1.87 times larger and 1.18 times more massive than Jupiter.
First discovered in 2016, it completes an orbit around its host star, the F6-type WASP-121 (TYC 7630-352-1), in just 1.3 days, as observed by the WASP-SOUTH SURVEY.
The WASP-121 system is situated about 881 light years away in the constellation of Puppis.
Characterized as an Ultra Hot Jupiter, WASP-121B orbits its parent star in a mere 1.3 days, being so close that the star’s gravitational pull begins to physically disrupt it.
Estimates suggest that the temperatures on the planet’s eternal daytime side exceed 3,000 degrees Celsius, while the nightside cools down to around 1,500 degrees Celsius.
“The discovery of silicon monoxide in the atmosphere of WASP-121B is revolutionary, marking the first definitive identification of this molecule in any planetary atmosphere,” stated Dr. Anjali Piette, an astronomer at the University of Birmingham.
“The composition of the nightside atmosphere of WASP-121B indicates vertical mixing: the transport of gases from deeper atmospheric layers to the peak observed in infrared light.”
“We were surprised to find methane on the nightside given the extreme temperatures of this planet.”
Measurements of carbon-to-hydrogen, oxygen-to-hydrogen, silicon-to-hydrogen, and oxygen-to-oxygen ratios in the atmosphere suggest that during its formation, WASP-121B’s atmosphere was enriched by inner rocky materials enhanced by erosion-resistant bombardment.
“They’re outstanding,” remarked Dr. Thomas Evans Soma, an astronomer at Newcastle University.
In their research, astronomers employed a method known as phase curve observation, which entails tracking a planet’s orbit around its star and analyzing variations in its brightness.
These observations reveal details about both the daytime and nighttime hemispheres, along with their chemical makeups.
“The successful detection of these elements and characterization of WASP-121B’s atmosphere with Webb showcases the telescope’s capabilities and sets a precedent for future exploratory research,” Dr. Piette remarked.
Study published today in the journal Nature Astronomy.
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TM Evans-Soma et al. Ultra-Stellar C/O ratio in the atmosphere of SIO and giant exoplanet WASP-121. Nature Astronomy Published online on June 2, 2025. doi:10.1038/s41550-025-02513-x
Source: www.sci.news
