The exoplanet WASP-127b, located 520 light-years from Earth, made headlines in January 2025 when astronomers measured its equatorial atmospheric motion at nearly 33,000 kilometers per hour. This figure, equivalent to 9 kilometers per second, was 16 times faster than the strongest winds recorded on Neptune, the wind champion of our solar system. However, the record lasted only 28 days before another exoplanet’s atmosphere was found to have even faster winds, reported on 18 February 2025.
A gas giant 520 light-years away has equatorial atmospheric
The initial measurement of WASP-127b’s winds relied on spectral analysis rather than direct observation. Researchers used CRIRES+, a high-resolution infrared spectrograph on the European Southern Observatory’s Very Large Telescope, to detect shifts in water vapor and carbon monoxide absorption lines during the planet’s transit. These shifts, caused by the Doppler effect, revealed two distinct peaks—one indicating gas moving toward Earth and the other moving away. This symmetry suggested an eastward equatorial jet, with the 33,000 km/h figure derived from a detailed retrieval model that accounted for the planet’s inflated atmosphere. The peer-reviewed analysis in Astronomy & Astrophysics calculated a jet velocity of 7.7 plus or minus 0.2 kilometres per second from the split peaks. That converts to about 27,700 kilometres per hour. A more detailed retrieval, which allowed the equatorial region, morning and evening limbs, and poles to make different contributions, placed equatorial atmospheric motion near 9 kilometres per second. This became the rounded public figure of 33,000 kilometres per hour.
The record was quickly overtaken by a study announced on 18 February 2025, though specifics about the new measurement remain unclear. The short-lived nature of the record highlights the challenges of comparing wind speeds across exoplanets, as different studies use varying methods to infer atmospheric dynamics. While WASP-127b’s winds were measured at 27,700 km/h in one analysis, the rounded public figure of 33,000 km/h became the widely cited benchmark.
Recent research using NASA’s James Webb Space Telescope (JWST) revealed a critical limitation in how exoplanet atmospheres are analyzed. A team studying a different hot gas giant, smaller than WASP-94A b, found that averaging spectral data across the entire planet’s atmosphere could significantly skew composition estimates. When the team resolved the morning and evening limbs of the planet, they discovered oxygen enrichment three to five times higher than the Sun’s, whereas a traditional single-sphere model incorrectly suggested 100 times higher enrichment. With the limbs resolved, we’ve got an oxygen enrichment of this planet that was three to five times higher than our Sun,
Mukherjee explains. When the team averaged the spectrum, the oxygen enrichment came out about 100 times higher.
JWST maps the weather on a hot gas giant
This bias, according to the study’s lead researcher, likely affects other tidally locked exoplanets, including sub-Neptunes and super-Earths. The team even managed to calculate how the atmosphere keeps the clouds aloft. The equatorial wind is apparently strong enough to push the heavy mineral droplets through the night side faster than gravity can pull them down. We need to think harder about how to mitigate this bias,
Mukherjee says. The answer, he suggests, might be figuring out how to disentangle morning and evening limbs in smaller planets based on the data we get from the instruments we have. And even if we don’t have this kind of measurements, we can think about how to develop our theoretical models to mitigate this even if we have an averaged spectrum of the planet,
Mukherjee claims. The findings, published in Science in 2026 (DOI: 10.1126/science.adx5903), underscore the importance of advanced observational techniques in understanding exoplanetary climates.
The rapid turnover of wind speed records and the discovery of compositional biases highlight the dynamic nature of exoplanet research. Future studies will likely focus on improving spectral analysis methods to resolve atmospheric asymmetries, as seen in the JWST’s work.
The scientific community continues to push the boundaries of what can be measured from Earth-based and space-based telescopes. As instruments like the JWST provide more detailed data, researchers will need to adapt their models to account for the complexities of exoplanetary atmospheres, ensuring that future discoveries are both accurate and meaningful.
