A new study has revealed the structure of extreme winds on WASP-121b, a gas giant located 1,300 light-years away.
This exoplanet is almost twice the size of Jupiter and orbits its star at a blistering 50 times closer than Earth orbits the Sun.
As a result, one side of WASP-121b is constantly facing its star, reaching scorching temperatures of 3,000°C (5,400°F), while the other side remains in perpetual darkness, with temperatures dropping by 1,500°C (2,700°F).
This extreme temperature difference generates violent winds that blow at thousands of meters per second, redistributing heat across the planet.
Until recently, scientists could only estimate wind speeds through indirect measurements.
However, thanks to advancements in telescopic technology, researchers have now directly measured wind speeds and their variations at different altitudes for the first time.
How scientists measured winds on a planet light-years away?
Led by Julia Seidel, researchers used ESPRESSO, one of the world’s most advanced spectrographs, mounted on the Very Large Telescope (VLT) in Chile’s Atacama Desert.
By combining the light from the VLT’s four massive 8-meter telescopes, they created an equivalent 16-meter telescope—larger than any optical telescope on Earth.
This powerful setup allowed them to analyze the planet’s light with extreme precision, separating it into 1.3 million wavelengths. This revealed how hydrogen, sodium, and iron in WASP-121b’s atmosphere absorb light, providing direct measurements of wind speeds.
Using the Doppler effect, the team discovered that:
- Iron moves at 5 km/s (11,000 mph) in a symmetrical pattern between the planet’s day and night sides.
- Sodium atoms move at 20 km/s (45,000 mph) along the equator, four times faster than iron.
- Hydrogen follows the sodium current but also escapes into space, likely carried by winds from the planet’s star.
This discovery is a major step toward understanding how planetary atmospheres work outside our solar system. The study provides new insights into hot Jupiters, giant exoplanets with temperatures over 1,000°C (1,800°F).
Such planets were first discovered in 1995 by Nobel Prize-winning astronomers Michel Mayor and Didier Queloz, challenging previous models of planet formation. Their discovery suggested that planets don’t always stay where they form, but instead migrate to different orbits.
Studying the atmospheres of hot Jupiters could help answer key questions:
- Where did these planets originally form?
- How far do they migrate?
- Why didn’t Jupiter migrate toward the Sun, potentially destroying Earth?
Currently, we rely on transit observations, where exoplanets pass in front of their stars, allowing us to study their atmospheres. However, past observations only provided averaged data, making it difficult to understand specific atmospheric conditions. This new study separated the planet’s eastern and western wind signals, offering an unprecedented level of detail.
Looking ahead, the Extremely Large Telescope (ELT)—set to begin operations in 2030—will have a 30-meter mirror, twice as large as the VLT setup. This telescope will allow scientists to study colder and smaller exoplanets, including rocky planets in habitable zones, where liquid water might exist.
With each new technological leap, we get closer to answering one of humanity’s greatest questions: Could other planets support life?
