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Artist\u2019s impression of an exoplanet with a magnetic field \u2013 credit, ESOM \/ Kornmesser, L. Cal\u00e7ada<\/p>\n Artist\u2019s impression of an exoplanet with a magnetic field \u2013 credit, ESOM \/ Kornmesser, L. Cal\u00e7ada<\/p>\n
For a planet to be habitable, it\u2019s generally considered to need liquid water. To have liquid water, a planet needs an atmosphere.<\/p>\n
To have an atmosphere, it\u2019s understood a world needs a magnetosphere, and for the first time ever, a team of astronomers has found the strongest evidence yet of magnetic fields\u2014like Earth and Jupiter, but unlike Mars\u2014around exoplanets.<\/p>\n
Indeed the departure of Mars\u2019 atmosphere and therefore his water is attributed to the departure of his magnetosphere.<\/p>\n
Observations on 7 very hot, Jupiter-like exoplanets made with the European Southern Observatory\u2019s<\/a> Very Large Telescope (ESO\u2019s VLT) and the Gemini North telescope, allowed astronomers to capture a key detail of planet formation and sustainment, but they had originally set out to simply measure the wind speeds on these distant worlds.<\/p>\n The researchers measured wind speeds on the worlds and determined that the winds on these planets are most likely governed by magnetic fields, providing the first robust measurement of magnetism on planets outside the solar system.<\/p>\n \u201cThis breakthrough opens a completely new window on exoplanet research. It\u2019s the first time we can compare the magnetic environments of other worlds\u2014a key step toward ultimately understanding which planets can stay alive, keep their water, and perhaps even, one day, host life as we know it,\u201d says Julia Seidel, an astronomer at the Laboratoire Lagrange, Observatoire de la C\u00f4te d\u2019Azur, France and lead author of the study published last week<\/a> in Nature Astronomy.<\/p>\n Earth\u2019s magnetic field influences our atmosphere in complex ways, and is therefore a key factor in understanding what keeps the planet habitable for life. Magnetic fields are also present in other Solar System planets, like Jupiter and Saturn. However, for the past 15 years, no one succeeded in directly measuring the strength of the magnetic fields of exoplanets.<\/p>\n Seidel and her team didn\u2019t actually set out to measure magnetic fields but winds. They measured wind speeds on 7 exoplanets orbiting different stars; all gas giants like Jupiter, but each tidally locked to its host star and very close to it. Just as we always see only one side of the Moon, these planets always keep one face towards the star, resulting in a scorching hot day side and a freezing cold night side.<\/p>\n This temperature difference creates a climate completely different from the one on our planet, with extremely strong winds. The wind speeds in their sample ranged from around 7,200 kilometers per hour\u00a0 to over 25,000 kmph; in comparison, the fastest winds measured on Jupiter reach speeds of around 1,500 kmph.<\/p>\n \u201cIn the beginning we set out to check if the atmospheric winds behaved the same way for all hot planets,\u201d explains Seidel. But when they looked at how the wind speeds varied with planet temperature, they saw a very intriguing pattern emerge: the hotter the planet, the slower the wind.<\/p>\n \u201cThis is totally counter intuitive because, all things being equal, hot planets have more energy to accelerate the winds! Something must happen that slows down the wind speeds for hotter objects,\u201d says study co-author Vivien Parmentier, a professor at the Laboratoire Lagrange.<\/p>\n