From European Southern Observatory(EU): “Powerful stratospheric winds measured on Jupiter for the first time”

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From European Southern Observatory(EU)

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Using the Atacama Large Millimeter/submillimeter Array (ALMA) [below], in which the European Southern Observatory (ESO) is a partner, a team of astronomers have directly measured winds in Jupiter’s middle atmosphere for the first time. By analysing the aftermath of a comet collision from the 1990s, the researchers have revealed incredibly powerful winds, with speeds of up to 1450 kilometres an hour, near Jupiter’s poles. They could represent what the team have described as a “unique meteorological beast in our Solar System”.

Jupiter is famous for its distinctive red and white bands: swirling clouds of moving gas that astronomers 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 atmospheric layers, in the stratosphere.

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, astronomers were provided with an alternative measuring aid in the form of comet Shoemaker–Levy 9, which collided with the gas giant in spectacular fashion in 1994.

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This image, taken with the MPG/ESO 2.2-metre telescope and the IRAC instrument, shows comet Shoemaker–Levy 9 impacting Jupiter in July 1994.
Credit: ESO

MPG Institute for Astronomy [Max-Planck-Institut für Astronomie](DE)/European Southern Observatory(EU) 2.2 meter telescope at Cerro La Silla, Chile, 600 km north of Santiago de Chile at an altitude of 2400 metres.

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 Laboratoire d’Astrophysique de Bordeaux(FR), 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 than twice the maximum storm speeds reached in Jupiter’s Great Red Spot and over three times the wind speed measured on Earth’s strongest tornadoes.

“Our detection indicates that these jets could behave like a giant vortex with a diameter of up to four times that of Earth, and some 900 kilometres in height,” explains co-author Bilal Benmahi, also of the Laboratoire d’Astrophysique de Bordeaux. “A vortex of this size would be a unique meteorological beast in our Solar System,” Cavalié adds.

Astronomers were aware of strong winds near Jupiter’s poles, but much higher up in the atmosphere, hundreds of kilometres above the focus area of the new study, which is published today in Astronomy & Astrophysics. Previous studies predicted that these upper-atmosphere winds would decrease in velocity and disappear well before reaching as deep as the stratosphere. “The new ALMA data tell us the contrary,” says Cavalié, adding that finding these strong stratospheric winds near Jupiter’s poles was a “real surprise”.

The team used 42 of ALMA’s 66 high-precision antennas, located in the Atacama Desert in northern Chile, to analyse the hydrogen cyanide molecules that have been moving around in Jupiter’s stratosphere since the impact of Shoemaker–Levy 9. The ALMA data allowed them to measure the Doppler shift — tiny changes in the frequency of the radiation emitted by the molecules — caused by the winds in this region of the planet. “By measuring this shift, we were able to deduce the speed of the winds much like one could deduce the speed of a passing train by the change in the frequency of the train whistle,” explains study co-author Vincent Hue, a planetary scientist at the Southwest Research Institute in the US.

In addition to the surprising polar winds, the team also used ALMA to confirm the existence of strong stratospheric winds around the planet’s equator, by directly measuring their speed, also for the first time. The jets spotted in this part of the planet have average speeds of about 600 kilometres an hour.

The ALMA observations required to track stratospheric winds in both the poles and equator of Jupiter took less than 30 minutes of telescope time. “The high levels of detail we achieved in this short time really demonstrate the power of the ALMA observations,” says Thomas Greathouse, a scientist at the Southwest Research Institute(US) and co-author of the study. “It is astounding to me to see the first direct measurement of these winds.”

“These ALMA results open a new window for the study of Jupiter’s auroral regions, which was really unexpected just a few months back,” says Cavalié. “They also set the stage for similar yet more extensive measurements to be made by the JUICE mission and its Submillimetre Wave Instrument,” Greathouse adds, referring to the European Space Agency’s JUpiter ICy moons Explorer, which is expected to launch into space next year.

ESO’s ground-based Extremely Large Telescope (ELT) [below], set to see first light later this decade, will also explore Jupiter. The telescope will be capable of making highly detailed observations of the planet’s aurorae, giving us further insight into Jupiter’s atmosphere.
More information

This research is presented in the paper published today in Astronomy & Astrophysics.

The team is composed of T. Cavalié (Laboratoire d’Astrophysique de Bordeaux(FR); Observatoire de Paris(FR), Paris Sciences et Lettres University(FR)), B. Benmahi (LAB), V. Hue (Southwest Research Institute [SwRI](US), R. Moreno, E. Lellouch (LESIA), T. Fouchet (LESIA), P. Hartogh (MPG institute for solar system research[Institut für Sonnensystemforschung][MPS](DE), L. Rezac (MPS), T. K. Greathouse (SwRI), G. R. Gladstone (SwRI), J. A. Sinclair (NASA JPL-Caltech(US)), M. Dobrijevic (LAB), F. Billebaud (LAB) and C. Jarchow (MPS).

See the full article here .


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European Southern Observatory (EU) is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre EEuropean Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

ESO Cerro LaSilla, 600 km north of Santiago de Chile at an altitude of 2400 metres.

ESO NTT at Cerro La Silla, Chile, at an altitude of 2400 metres.

ESO VLT at Cerro Paranal in the Atacama Desert, •ANTU (UT1; The Sun ),
•KUEYEN (UT2; The Moon ),
•MELIPAL (UT3; The Southern Cross ), and
•YEPUN (UT4; Venus – as evening star).
elevation 2,635 m (8,645 ft) from above Credit J.L. Dauvergne & G. Hüdepohl atacama photo.

Glistening against the awesome backdrop of the night sky above ESO’s Paranal Observatory, four laser beams project out into the darkness from Unit Telescope 4 UT4 of the VLT, a major asset of the Adaptive Optics system.

ESO/National Radio Astronomy Observatory(US)/National Astronomy Observatory of Japan(JP) ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres.

ESO ELT 39 meter telescope to be on top of Cerro Armazones in the Atacama Desert of northern Chile. located at the summit of the mountain at an altitude of 3,060 metres (10,040 ft).

European Southern Observatory(EU)/Max Planck Institute for Radio Astronomy(DE) APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft).

A novel gamma ray telescope under construction on Mount Hopkins, Arizona. a large project known as the Čerenkov Telescope Array, composed of hundreds of similar telescopes to be situated in the Canary Islands and Chile. The telescope on Mount Hopkins will be fitted with a prototype high-speed camera, assembled at the University of Wisconsin–Madison(US), and capable of taking pictures at a billion frames per second. Credit: Vladimir Vassiliev.