Astronomers detected a supersonic wind with record speed on an exoplanet.

Observing the weather on planets in distant systems is quite a challenging task. To construct models of the physical and chemical processes in the atmosphere, scientists utilize spectrophotometric data, examining how the gas layers of a far-off astronomical body absorb, reflect, and refract the light from its star.

Transit planets, whose flight path lies between us and their star, are best suited for such observations. Preference is given to bodies with short orbital periods of up to two Earth days, as they exhibit a more significant change in the angle of view during transit, allowing for the collection of extensive data. Previously, researchers studied the weather on WASP-121b, a planet with an orbital period of just 31 hours.

The object of the new study has an orbital period of 4.18 Earth days. The hot Jupiter WASP-127b orbits a star of spectral class G, which is the same class as our Sun. This gas giant has a radius 1.31 times that of Jupiter but is considerably less massive at 0.16 times Jupiter's mass. The density of its "bloated" atmosphere is one of the lowest recorded in the history of exoplanet observations, making it an excellent target for study.

Transit observations of WASP-127b were carried out in March 2022 using the CRIRES+ spectrograph at the VLT observatory in Chile. The results of the analysis of the obtained 98 spectra have been published in the journal Astronomy & Astrophysics.

It turned out that at the equator of WASP-127b, there is an airflow moving at a speed close to nine kilometers per second, or about 7.7 kilometers per second if we subtract the estimated rotational speed of the planet itself (similar to how we calculate wind speeds in the atmospheres of Earth or Jupiter). In both cases, this is currently known as the fastest flow of its kind in the universe.

The planet is in tidal lock, meaning one side is always facing the star while the other half experiences eternal night. In just 10.4 hours, the equatorial wind sweeps across the dark side, completing a full rotation around the planet in 0.87 days, or 20.88 hours. The wind speed at the equator is six times greater than what a calm atmosphere would exhibit at this rotational speed. For comparison, the record wind speed at the equator of Saturn is 0.43 kilometers per second.

Additionally, scientists confirmed that there is water in the planet's atmosphere, but most importantly, they detected carbon monoxide for the first time. Previous studies had proposed unusual hypotheses regarding the planet's formation to explain the lack of carbon monoxide. It turns out that the elemental ratio on the exoplanet WASP-127b is quite standard.

“Understanding the dynamics occurring on such planets helps us study the mechanisms of heat distribution and chemical processes, enhancing our knowledge of planet formation and potentially shedding light on the origins of our Solar System,” explained co-author David Kont, an exoplanet atmosphere researcher from Ludwig Maximilian University of Munich (Germany).

Notably, only ground-based observatories can conduct such observations today. Space telescopes lack the resolution needed to measure speeds with sufficient accuracy. The ANDES instrument on the ELT telescope will allow for even more detailed studies of weather on exoplanets. This telescope, currently under construction in Chile, is expected to see its "first light" in 2028.