At first glance, giant planets called super-Jupiters might seem like close cousins of Jupiter. Some are even ten times more massive.
For years, astronomers assumed their atmospheres behaved much like Jupiter’s—with stable east–west stripes, huge storms, and predictable weather patterns.
But new results from the James Webb Space Telescope (Webb) are rewriting that idea.
An international research team, including astronomer Stanimir Metchev from Western University, has discovered that some super-Jupiters form enormous dust storms that look nothing like the swirling storms on Jupiter.
Their findings, published in Science Advances, show that the atmospheric dynamics of these massive worlds follow a very different playbook.
Super-Jupiters are a type of brown dwarf—objects heavier than planets but too light to ignite into stars.
They cool over billions of years and eventually reach temperatures similar to giant planets, making them excellent stand-ins for studying exoplanet atmospheres.
Because they share properties with planets but can be observed more easily, they help scientists test ideas about how alien worlds behave.
For more than a decade, Metchev and his colleagues have studied storms on brown dwarfs and found that dust clouds are extremely common. One unusual brown dwarf, VHS 1256B, has been of special interest.
Previous observations with Webb revealed that this super-Jupiter shows dramatic brightness changes over time—a sign of intense atmospheric activity.
Researchers believed these variations came from massive dust clouds rising and falling, creating “weather” far more extreme than anything seen in our solar system.
To understand what drives this changing brightness, the team built detailed computer simulations of VHS 1256B’s atmosphere and compared their model to real Webb data.
The results were surprising. Instead of producing Jupiter-like rings and long-lasting storms such as the Great Red Spot, VHS 1256B’s atmosphere is shaped by powerful equatorial waves.
These waves arise when clouds near the equator absorb heat, warming the atmosphere unevenly. The imbalance triggers large-scale east–west motions that carry dust around the planet, forming huge moving storms. This process, called cloud-radiative feedback, explains both the short-term flickering in brightness and the slower, long-term changes in VHS 1256B’s light.
Lead author Xianyu Tan explains that this theory had been proposed before, but direct observations were needed to prove it. The match between the model and Webb’s data confirms that these wave-driven storms really exist. While other atmospheric processes could still play a role, this new mechanism appears to be a major driver of super-Jupiter weather.
Why do these planets behave so differently from Jupiter? The key is temperature. Super-Jupiters like VHS 1256B are much hotter.
Their atmospheres react to radiation more quickly, preventing the formation of Jupiter’s famous banded structure. On Jupiter, cooler temperatures allow slow-moving turbulence to build its distinctive stripes. On super-Jupiters, heat destabilizes this pattern and instead generates fast-moving waves and shifting dust storms.
These findings shed new light on one of planetary science’s biggest mysteries: how giant planets circulate heat and form weather systems. As collaborator Xi Zhang notes, super-Jupiters provide a new and powerful window into understanding atmospheric circulation in worlds across the galaxy.
Thanks to Webb, we are discovering that even planets that look similar from afar can behave in wildly different ways—making the universe far more diverse and surprising than we imagined.
Source: KSR.
