For the first time, the tool for finding planets light-years away was used on an object in the Solar System during the study of Jupiter’s winds. We are at a time when the discovery of planets orbiting another star has become almost commonplace, with more than 5,000 reported. The first distant worlds to make the list were mostly giant planets similar to Jupiter and Saturn, but they were also very different from us. them in many ways

Astrophysicists have already begun collecting data on the atmospheres of exoplanets, but there are still no answers to fundamental questions about the atmosphere of the largest planet in the Solar System. To understand what is happening in Jupiter’s clouds and atmosphere, it is necessary to study it with continuous observations over a long period of time.

For the first time, an instrument designed to search for and analyze light-year worlds, exoplanets, has been aimed at a target in the Solar System, the planet Jupiter, 43 light-minutes from Earth.

Researchers from the Institute of Astrophysics and Space Sciences (IA) at the Faculty of Science of the University of Lisbon (Ciências ULisboa) used the ESPRESSO spectrograph mounted on the VLT telescope at the European Southern Observatory (ESO) to measure the wind speed on Jupiter. The results are now published in the journal Universe.

The method developed by the team is called Doppler velocity measurement and is based on the reflection of visible light from the sun by clouds in the target planet’s atmosphere. This reflected light bends in wavelength proportional to the speed at which the clouds move relative to the telescope on Earth. This gives the instantaneous wind speed at the observed point.

The method currently used with ESPRESSO was developed by the IA Planetary Systems Research Group in conjunction with other spectrographs to study the atmosphere of Venus. Researchers have been measuring this nearby planet’s winds and modeling its overall atmosphere for several years.

The application of this method for exploratory purposes with a “highest range” device such as ESPRESSO has paved the way for a seminal breakthrough in understanding our cosmic neighborhood. This study confirms the feasibility of systematically monitoring the most distant atmospheres of gaseous planets.

For five hours in July 2019, the team pointed the VLT telescope at Jupiter’s equatorial region, where light clouds are found at higher altitudes, as well as at the planet’s northern and southern equatorial belts, where they form bands that correspond to sinking air. It consists of darker, warmer clouds in a deeper layer of the atmosphere.

“Jupiter’s atmosphere at the level of clouds visible from Earth contains ammonia, ammonium hydrosulfide and water, which form light red and white bands,” says Pedro Machado of IA and Ciências ULisboa. “The upper clouds are located in the pressure zone from 0.6 to 0.9 bar, consisting of ammonia ice. “Water clouds form the densest, lowest layer and have the strongest influence on the dynamics of the atmosphere,” adds the researcher.

With ESPRESSO, the team was able to measure winds on Jupiter from 60 to 428 km/h with an error of less than 36 km/h. These observations, applied to the gaseous planet with a high-resolution instrument, have their own challenges: “One of the challenges centers on ‘orientation finding’ in Jupiter’s disk, that is, knowing exactly where we are pointing in the planet’s disk with the enormous resolution of the VLT telescope,” explains Pedro Machado.

“The difficulty in the study itself was that we determined winds down to a few meters per second at a time when Jupiter’s rotation at the equator was about ten kilometers per second, and what complicated the situation was that it was a gaseous planet, not a gaseous planet. “A single solid body depends on the latitude of the point where we observe it,” the researcher said. “It rotates at different speeds,” he adds.

To test the effectiveness of Doppler velocity measurement from telescopes on Earth for measuring wind on Jupiter, the team also collected measurements taken in the past to compare the results. Most of the available data was collected by instruments in space, and a different method was used to obtain average wind speed values ​​by tracking the structure of clouds in images taken in the near future.

The consistency between the values ​​measured in this story and the published study supports the feasibility of applying Doppler velocity measurement to a program to monitor Jupiter’s winds from Earth.

The monitoring will allow the research team to collect data on how winds change over time and will be important for developing a reliable model of the global circulation of Jupiter’s atmosphere.

This computational model should reproduce the variation in winds depending on Jupiter’s latitude and storms to help understand the causes of the atmospheric phenomena we observe on this planet. Conversely, the model will help prepare for future observations with information about the pressure and height of clouds in the telescope’s view.

In addition to expanding ESPRESSO’s observations to cover more of Jupiter’s disk, the team plans to temporarily collect wind data during the planet’s approximately 10-hour rotation period. Restricting observations to specific wavelength ranges will also allow winds to be measured at different altitudes, thus providing information about the vertical movement of air layers.

Once the technique is mastered for the Solar System’s largest planet, the team hopes to apply it to the atmospheres of other gaseous planets; The next target is Saturn.

The success of these observations with ESPRESSO turns out to be important at a time when its successor ANDES is being designed for the future Extremely Large Telescope (ELT), also owned by ESO, currently under construction in Chile, and the future JUICE mission. The European Space Agency is dedicated to Jupiter and will provide additional data.