Thanks to ESO's Very Large Telescope, the magnetic fields of exoplanets have been measured

Scientists continue to gather data to understand the evolution of exoplanets and their potential in the development of extraterrestrial life. Thanks to the Very Large Telescope (VLT) of the European Southern Observatory in Chile and the Gemini North telescope located in Hawaii, it was possible for the first time in the history of astronomy to measure the magnetic fields of exoplanets.

The data related to this discovery has been included in the study titled Magnetic field strengths of hot giant exoplanets consistent with Solar System values. To achieve this result, researchers analyzed winds present on known exoplanets and, using the Very Large Telescope and the Gemini North telescope, measured their speeds on seven gas giants, similar to Jupiter, each in synchronous rotation with their own star. This means that one side is permanently exposed to the heat of the star, while the other is immersed in perpetual darkness.

The winds on exoplanets and the analyses of ESO's Very Large Telescope

The results were surprising and definitely interesting. The measured speeds ranged from around 7200 km/h to over 25000 km/h. These values are higher than those we have managed to measure in the Solar System, where Jupiter can only reach speeds of 1500 km/h.

However, the analysis of the data also led to a surprise. During the measurements, it was noticed that the hottest exoplanets had a lower wind speed. This was an unexpected result, as the available energy in the system should be greater and thus capable of accelerating the winds themselves. Vivien Parmentier (professor at the Laboratoire Lagrange and co-author of the study) stated, "this is totally counterintuitive because, all else being equal, hotter planets have more energy to accelerate the winds! There must be something that slows down the wind speed in the hotter objects."

The answer to this phenomenon is still unclear, but there are some hypotheses. One of the most plausible explanations is that the presence of strong magnetic fields can slow down the charged particles present in the atmosphere. Based on the data, it was thus possible to estimate the intensity of the magnetic fields of each exoplanet, finding values comparable to those of our Solar System, that is four times stronger than those of Saturn or about half of those of Jupiter.

Julia Seidel (astronomer at the Laboratoire Lagrange of the Observatoire de la Côte d'Azur) added, "this groundbreaking discovery opens up a completely new perspective on the research dedicated to exoplanets. It is the first time we can compare the presence of magnetic fields in the environment of other worlds: a fundamental step in understanding which planets can remain habitable, retain water, and perhaps one day host life as we know it."

Clearly, one cannot miss a comparison with Earth and the life that has developed here, but it is also another way to learn about exoplanets, their variety in the Universe, and to gain a better understanding of what surrounds us.

Not only the search for life, but the implications go beyond biology. In fact, such intense magnetic fields could generate phenomena similar to our auroras, which are also present on other planets in the Solar System. Observing phenomena of this type is not only spectacular to behold but also useful in understanding the interaction between a star and an exoplanet, providing further information on the very structure of the stellar system.

The contribution of the Very Large Telescope has been fundamental, but the focus is on the future, particularly the ELT, the Extremely Large Telescope of ESO. This new scientific instrument will allow extending this type of investigation to smaller planets, similar to Earth, and to analyze atmospheric gases that could produce auroras on even more distant worlds.