Free Astronomy Magazine July-August 2021

18 JULY-AUGUST 2021 ASTRO PUBLISHING tacular fashion in 1994. This impact produced new molecules in Jupiter’s stratosphere, where they have been moving with the winds ever since. A team of astronomers, led by Thibault Cavalié of the Lab- oratoire d’Astrophysique de Bordeaux in France, have now tracked one of these molecules — hydrogen cyanide — to directly measure stratospheric “jets” on Jupiter. Scientists use the word “jets” to refer to narrow bands of wind in the atmosphere, like Earth’s jet streams. “The most spectacular result is the presence of strong jets, with speeds of up to 400 metres per second, which are located under the aurorae near the poles,” says Cavalié. These wind speeds, equivalent to about 1450 kilometres an hour, are more Powerful stratospheric winds measured on Jupiter for the first time J upiter is famous for its distinctive red and white bands: swirling clouds of moving gas that as- tronomers traditionally use to track winds in Jupiter’s lower atmosphere. Astronomers have also seen, near Jupiter’s poles, the vivid glows known as aurorae, which appear to be associated with strong winds in the planet’s upper atmosphere. But until now, researchers had never been able to directly measure wind patterns in between these two at- mospheric layers, in the strato- sphere. Measuring wind speeds in Jupiter’s stratosphere using cloud-tracking techniques is impossible because of the absence of clouds in this part of the atmosphere. However, as- tronomers were provided with an al- ternative measuring aid in the form of comet Shoemaker–Levy 9, which collided with the gas giant in spec- by ESO - Bárbara Ferreira