Scientists analyzing an ultra-hot giant planet believe it was formed by absorbing lightweight gases like methane evaporating from tiny space pebbles, while being bombarded with large rocky objects.
They also found methane (CH₄) in the planet’s “nightside” atmosphere.
“The ‘nightside’ atmospheric composition of WASP-121b also suggests ‘vertical mixing’—the transport of gas from deeper atmospheric layers to the infrared photosphere.
Given how hot this planet is, we weren’t expecting to see methane on its nightside.”
These observations provide a view of both the dayside and nightside hemispheres, and their chemical makeup.
Scientists studying an extremely hot giant planet think it formed as a result of being hit by large rocky objects and absorbing light gases like methane that evaporated from tiny space pebbles.
Water (H2O), carbon monoxide (CO), and silicon monoxide (SiO) were successfully detected on the “dayside” of WASP-121b, the side facing its star, by researchers using the James Webb Space Telescope (JWST) to study the planet’s atmosphere. In the “nightside” atmosphere of the planet, they also discovered methane (CH₄).
The international research team’s findings, which were published in Nature Astronomy, are the first to definitively identify SiO in any planetary atmosphere, either inside or outside of our solar system.
Due to its orbital distance of only roughly twice the star’s diameter, WASP-121b has an eternal dayside with temperatures locally exceeding 3,000 degrees Celsius and a nightside with temperatures as low as 1,500 degrees.
“This is the first definitive identification of SiO in any planetary atmosphere, and its detection in the atmosphere of WASP-121b is revolutionary,” said Dr. Anjali Piette, a co-author from the University of Birmingham.
Additionally, WASP-121b’s ‘nightside’ atmospheric composition points to’vertical mixing,’ which is the movement of gas from deeper atmospheric layers to the infrared photosphere. We didn’t anticipate seeing methane on this planet’s nightside because of how hot it is. “.
As indicated by the measured atmospheric carbon-to-hydrogen (C/H), oxygen-to-hydrogen (O/H), silicon-to-hydrogen (Si/H), and carbon-to-oxygen (C/O) ratios, the atmosphere of WASP-121b was enriched by inward-drifting pebbles in addition to a barrage of refractory material during its formation.
“Dayside temperatures are high enough for refractory materials—usually solid compounds resistant to strong heat—to exist as gaseous components of the planet’s atmosphere,” wrote Dr. Thomas Evans-Soma, the lead author, who was from the University of Newcastle in Australia.
A method known as phase curve observation, which involves tracking the planet as it revolves around its star to observe changes in brightness, was employed by scientists to examine the atmosphere of WASP-121b. These findings offer insight into the chemical composition of the dayside and nightside hemispheres.
“The effective utilization of JWST to identify these components and describe the atmosphere of WASP-121b showcases the telescope’s potential and establishes a standard for upcoming exoplanet research,” Dr. Piette continued.
