This artist’s visualisation of WASP-127b, a giant gas planet located about 520 light-years from Earth, shows its newly discovered supersonic jet winds that move around the planet’s equator. With a speed of 9 km per second (33 000 km/h), this is the fastest jetstream of its kind ever measured in the Universe. By tracking the speed of molecules in the atmosphere with the CRIRES+ instrument on ESO’s Very Large Telescope, researchers found that one side of the planet’s atmosphere is moving towards us and the other away from us. This indicates that there is a powerful wind current going around the planet. (Credit: ESO/L. Calçada)
Scientists detect fastest planetary jet stream ever measured
In a nutshell
- Astronomers have detected the fastest planetary winds ever measured in a supersonic jet stream racing at 33,000 kilometers per hour around the equator of WASP-127b, fast enough to circle Earth in about an hour. For comparison, the fastest winds in our solar system (on Neptune) reach only 1,800 kilometers per hour.
- The planet shows dramatic temperature differences between regions: its morning side is 175 Kelvin cooler than its evening side, while its poles are significantly colder than its equator. This creates a complex weather system unlike anything seen in our solar system.
- WASP-127b is an unusual “puffy” planet. While slightly larger than Jupiter, it has only 7% of Jupiter’s density, making it one of the least dense planets ever discovered. This unique characteristic allowed astronomers to study its atmosphere in unprecedented detail.
GÖTTINGEN, Germany — Five hundred light-years from Earth, a distant exoplanet experiences weather patterns that make Earth’s most violent hurricanes look like gentle breezes. On WASP-127b, supersonic winds from the fastest planetary jet stream ever measured tear around the equator at 33,000 kilometers per hour, according to a study from the University of Göttingen. That’s nearly six times faster than the planet’s rotation, dwarfing the fastest winds ever recorded in our entire solar system.
The research, published in Astronomy & Astrophysics, documents the extraordinary weather on WASP-127b. Its equatorial winds move faster than sound itself (similar to how a supersonic jet breaks the sound barrier), while the planet’s north and south poles stay unusually cold compared to their surroundings. To put this in perspective, it would be like having a permanent band of hypersonic winds circling Earth’s equator while maintaining frozen poles, but at a much more extreme scale.
“Part of the atmosphere of this planet is moving towards us at a high velocity while another part is moving away from us at the same speed,” says lead author Lisa Nortmann, scientist at the University of Göttingen, in a statement. “This signal shows us that there is a very fast, supersonic, jet wind around the planet’s equator.”
WASP-127b stands out among known planets. It’s a gas giant with just 7% of Jupiter’s density, making it one of the “puffiest” planets ever discovered. Though slightly larger than Jupiter, it has only a fraction of its mass. Orbiting its Sun-like star every 4.2 days at extremely close range, this ultra-low-density world provides astronomers with an exceptional opportunity to study atmospheric dynamics.
The wind speeds detected exceed anything seen in our solar system. For comparison, the fastest winds ever measured in our cosmic neighborhood were found on Neptune, moving at “only” 1,800 kilometers per hour. At 9 kilometers per second, WASP-127b’s equatorial jet stream moves at nearly six times the speed at which the planet rotates.
During a 6.6-hour observation, researchers used the CRIRES+ instrument on the Very Large Telescope in Chile to study WASP-127b as it transited its star. This instrument analyzes infrared light at extremely high resolution—about 140,000 times more detailed than what the human eye can see. This transit method allows scientists to analyze starlight filtered through the planet’s atmosphere, revealing its chemical composition and atmospheric motion patterns.
The team detected clear signatures of water vapor and carbon monoxide in the planet’s atmosphere. These chemical signatures appeared as two distinct peaks in their data, indicating that one side of the atmosphere moves toward Earth while the other moves away at high speed. This split signal revealed the powerful equatorial jet stream moving at supersonic velocities.
Another key finding was the striking temperature variations across the planet’s surface. The morning terminator measured about 175 Kelvin cooler than the evening terminator, while the polar regions appeared up to 624 Kelvin cooler than the equatorial zones.
What is a terminator?
A terminator, sometimes called a “terminator line,” is the dividing line between the day and night sides of a planet. Think of it like the line of sunset or sunrise moving across Earth. There are two terminators on a planet:
- The morning terminator (or “dawn terminator”): where night transitions into day
- The evening terminator (or “dusk terminator”): where day transitions into night
In the case of WASP-127b, the terminators are particularly important because:
- The planet is believed to be “tidally locked,” meaning one side always faces its star (permanent day) while the other side faces away (permanent night)
- The researchers found that the morning terminator was about 175 Kelvin cooler than the evening terminator
- This temperature difference tells us about how heat is distributed around the planet
“Understanding the dynamics of these exoplanets helps us explore mechanisms such as heat redistribution and chemical processes, improving our understanding of planet formation and potentially shedding light on the origins of our own Solar System,” explains co-author David Cont from Ludwig Maximilian University of Munich.
These findings highlight the rapid advancement of exoplanet research. While scientists could previously only measure basic properties like mass and radius, new instruments like CRIRES+ now enable detailed mapping of atmospheric composition and weather patterns on distant worlds. Future telescopes, like ESO’s Extremely Large Telescope currently under construction in Chile, will allow researchers to study even finer details of wind patterns and expand this research to smaller, rocky planets.
Paper Summary
Methodology
The researchers used high-resolution spectroscopy during a transit of WASP-127b, when the planet passed between its star and Earth. They analyzed how different wavelengths of starlight were absorbed by molecules in the planet’s atmosphere, focusing on the K-band portion of the infrared spectrum. They then used sophisticated computer modeling and statistical analysis to interpret the spectral signals and determine the atmospheric properties of different regions of the planet.
Results
The study found supersonic equatorial winds moving at 7.7 kilometers per second, detected both water vapor and carbon monoxide in the atmosphere, and discovered significant temperature differences between the planet’s equatorial and polar regions. The chemical composition was found to be similar to solar values, contradicting previous studies suggesting unusual chemistry.
Limitations
The study was based on observations during a single transit event lasting 6.6 hours. The researchers had to make some simplifying assumptions about the atmosphere’s structure, and their measurements were limited to the portions of the atmosphere visible during transit.
Discussion and Takeaways
This research provides the first clear evidence of latitudinal temperature variations on an exoplanet and demonstrates that atmospheric circulation patterns predicted by theoretical models actually exist in nature. The findings suggest that hot Jupiter exoplanets may commonly feature supersonic equatorial jets and cooler polar regions.
Funding and Disclosures
The project was supported by multiple institutions including the Deutsche Forschungsgemeinschaft, the Federal Ministry of Education and Research (Germany), and the Knut and Alice Wallenberg Foundation. The research used observations from the European Southern Observatory’s Very Large Telescope.
Publication Information
Published in Astronomy & Astrophysics (A&A, 693, A213, 2025). Authors: L. Nortmann et al.
