For the first time ever, astronomers have measured winds in Jupiter’s middle atmosphere, revealing unexpectedly fast jet currents in the planet’s deeper layers.
A paper published in Astronomy & Astrophysics gives new meaning to the term ‘polar vortex’.
Using the Atacama Large Millimeter / submillimeter Array (ALMA) in Chile, astronomers have clocked the speed of polar rays far below the cloud tops, and, Wow, is it ever gusty there? The fastest of these jets moves at 895 miles per hour (1,440 km / h), which is nearly five times faster than the winds produced by the strongest hurricanes on Earth.
Thibault Cavalié, the study’s lead author and a planetary scientist at the Laboratoire d’Astrophysique de Bordeaux in France, said these jets, found beneath Jupiter’s major auroras (yes, Jupiter has auroras, and they’re pretty amazing), appear to be the “bottom tail of the supersonic jets seen 900 miles.” [560 miles] above, ”as he explained in an email. These currents could form a “huge anticyclone with a diameter of 3 to 4 Earth diameters and a vertical dimension of 900 km,” said Cavalié, adding, “This is unique in the solar system.”
In a pronunciation Released by the European Southern Observatory, Cavalié described the newly discovered element as a “unique meteorological beast”.
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Measuring wind speed below Jupiter’s upper atmospheric layer is not easy. The iconic red and white bands that run across Jupiter are mostly used to measure the wind in the upper layer, and the planet’s auroras, which are linked to strong winds in the upper atmosphere, are also used as reference points. But to be fair, scientists haven’t really been able to measure the winds in Jupiter’s middle atmosphere – the stratosphere – until now.
Two things made these measurements possible: a famous comet and a very powerful telescope.
The comet in question is Shoemaker-Levy 9, which collided with Jupiter in 1994. The impact left distinctive molecules in the atmosphere, and they have been blowing around the gas giant for 27 years. The presence of these molecules – namely hydrogen cyanide – made it possible for Cavalié and his colleagues to see under the cloud tops and measure the speed of stratospheric jet streams.
To detect these molecules, the team used 42 of ALMA’s 66 high-precision antennas, marking the first time scientists have made such measurements in Jupiter’s middle atmosphere.
Specifically, the ALMA data enabled the scientists to measure small frequency changes in the radiation emissions from molecules as they are blown into this part of the planet by winds. In other words, they measured the Doppler shift. By doing this, “we were able to derive the speed of the wind as you could infer the speed of a passing train by the change in the frequency of the train whistle,” explains Vincent Hue, a planetary scientist at the Southwest Research Institute. and a co-author of the new study, in the ESO statement.
These measurements showed that winds beneath the auroras near the poles were moving at a speed of 895 mph, which is more than twice the speed of winds swirling around the planet’s Great Red Spot. To At the equator, stratospheric winds were clocked at an average speed of 373 mph (600 km / h).
High-speed winds had previously been observed in the upper atmospheric layer, but scientists thought so the deeper you go, the slower you go, as far as wind speeds are concerned. The new research suggests otherwise, a finding that came as a complete surprise to the team.
The newly detected winds are fast, but they are neither the fastest in the solar system the fastest on Jupiter. The winds observed under Jupiter’s aurora are “twice as fast as the fastest winds measured at Jupiter’s cloud top,” Cavalié said. But ‘higher up’ and ‘still below the aurora in a layer called the ionosphere’, there are ‘winds at supersonic speeds of 1 to 2 kilometers per second [0.62 to 1.24 miles per second], ”Or 2,240 to 4,475 mph 3,600 to 7,200 km / hNeptune, he added, “has the strongest winds in the solar system at cloud level, and they are 25% faster than the winds we measured under the aurora.”
This study, in addition to measuring winds in Jupiter’s stratosphere, was done as a proof-of-concept for similar studies to be conducted by the Submillimetre Wave Instrument (SWI) on board the upcoming Jupiter Icy Moons Explorer (JUICE). Launched next year, it will be the first European mission to Jupiter, expected to arrive in about 10 years.