A distant planet known as WASP-121b has helped scientists uncover new clues about how giant planets form—and it turns out, tiny space pebbles and massive rocks may have played a major role.
By using the powerful James Webb Space Telescope (JWST), researchers observed this ultra-hot gas giant and found evidence of water, carbon monoxide, and silicon monoxide in its atmosphere.
They also made a surprising discovery: methane on the cooler side of the planet.
WASP-121b is an extreme world. It orbits its star so closely that one side always faces the star, baking at temperatures over 3,000 degrees Celsius.
The other side, forever in darkness, is still scorching at about 1,500 degrees.
This setup gives scientists a rare opportunity to study both the day and night sides of a planet and compare their atmospheres.
In a breakthrough study published in Nature Astronomy, researchers reported the first clear detection of silicon monoxide (SiO) in any planet’s atmosphere—something that’s never been confirmed before, even within our own solar system.
Dr. Anjali Piette from the University of Birmingham called it “groundbreaking,” and noted how surprising it was to also find methane (CH₄) on the planet’s nightside.
Methane usually doesn’t survive such high temperatures, so its presence suggests a process called vertical mixing—where gases from deeper layers of the atmosphere rise to the surface.
The discovery doesn’t just add new molecules to the catalog of space chemistry; it also reveals how the planet may have formed.
The mix of elements detected—especially the ratios of carbon, oxygen, silicon, and hydrogen—suggests that WASP-121b was formed in part by drawing in gases like methane from drifting pebbles, and by being struck with heat-resistant rocky materials.
These rocky impacts likely enriched the planet’s atmosphere with heavy elements.
To capture this detailed picture, the research team used a method called phase curve observation, watching how the planet’s brightness changed as it orbited its star. This allowed them to see both sides of the planet and track how its atmosphere shifts from day to night.
According to Dr. Piette, the study proves just how powerful the JWST is for studying distant worlds. These kinds of discoveries open the door to learning more about how planets form, evolve, and what might make them truly unique.
Source: University of Birmingham.
