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Photo: ESO/M. Kornmesser, L. Calzada
Astronomers have discovered the first evidence of magnetic fields around planets outside our solar system by studying their high-speed and powerful winds. This is the first direct measurement of the magnetic field strength of an exoplanet and a major step forward in exoplanet research.
Since life on Earth is made possible by our planet's magnetosphere, which protects it from harmful solar radiation, this research could also be useful in the search for life beyond the solar system.
Using the Very Large Telescope (VLT) and the Gemini North telescope, the team behind this discovery measured the wind speeds of seven extremely hot, tidally locked gas giant exoplanets similar to Jupiter, meaning they have a constantly hot "day side" and a cooler, space-facing "night side." The team found wind speeds ranging from 4,470 mph (7,194 kilometers per hour) to an astonishing 15,530 mph (24,993 km/h). By comparison, the fastest winds recorded on Jupiter in our solar system reached only about 930 mph (1,496 km/h). Scientists believe that the magnetic fields of these exoplanets drive these winds.
This image shows the exoplanet's magnetic activity. | Credit: ESO/M. Kornmesser, L. Calçada
Astronomers have discovered the first evidence of magnetic fields around planets outside our solar system by studying their high-speed and powerful winds. This is the first direct measurement of the magnetic field strength of an exoplanet and a major step forward in exoplanet research.
Since life on Earth is made possible by our planet's magnetosphere, which protects it from harmful solar radiation, this research could also be useful in the search for life beyond the solar system.
Using the Very Large Telescope (VLT) and the Gemini North telescope, the team behind this discovery measured the wind speeds of seven extremely hot, tidally locked gas giant exoplanets similar to Jupiter, meaning they have a constantly hot "day side" and a cooler, space-facing "night side." The team found wind speeds ranging from 4,470 mph (7,194 kilometers per hour) to an astonishing 15,530 mph (24,993 km/h). By comparison, the fastest winds recorded on Jupiter in our solar system reached only about 930 mph (1,496 km/h). Scientists believe that the magnetic fields of these exoplanets drive these winds.
«"This breakthrough opens completely new horizons in exoplanet research. For the first time, we can compare the magnetic environments of other worlds—a key step toward understanding which planets could remain habitable, retain water, and perhaps even one day harbor life as we know it," said team member Julia Seidel, an astronomer at the Lagrange Laboratory, Côte d'Azur Observatory in France, in a statement.
The hotter the planet, the stronger its winds.
At the beginning of the study, the team didn't even consider magnetic fields. The initial goal was to determine whether winds were the same on all hot planets. However, the researchers' curiosity was piqued when they discovered that wind speeds appeared to vary depending on the planet's temperature. Surprisingly, the team found that the colder the planet, the faster and stronger its winds.
«"This is completely counterintuitive, because, all other things being equal, hot planets have more energy to accelerate winds!" team member Vivienne Parmentier said in a statement. "Something must be happening to slow down the wind speed on hotter objects.".
The planets pictured here are gas giants like Jupiter, but they are tidally locked: one side is constantly facing the star and is therefore much hotter than the other. This temperature difference generates powerful winds from the dayside to the nightside. We expect these winds to be faster on planets that are generally hotter, as they have more energy to support them. This is shown in the top row of the diagram: the hotter planet on the right has faster winds, indicated here by the velocity meter. In the bottom row of the diagram, the hotter planet on the right has slower winds than the cooler planet. | Source: ESO/M. Kornmesser, L. Calçada
Parmentier and his colleagues concluded that this unintuitive inverse relationship between temperature and wind speed is a result of the global magnetic fields on these planets. These fields act as brakes, slowing down charged particles. This means that wind speed can be used to determine the strength of these exoplanets' magnetic fields.
The team found that the magnetic fields of seven exoplanets are approximately four times stronger than those of the solar system's gas giant Saturn and about half as strong as those of Jupiter. This means these worlds could also host stunning and colorful auroras that outshine Earth's northern and southern lights.
«"Here on Earth, we know the beauty of the northern and southern lights, when particles from the Sun collide with our magnetic field and are directed toward the poles, colliding with gases in the atmosphere and creating colorful displays of green, pink, and purple," said team member Bibiana Prinot of the European Southern Observatory (ESO) in Garching, Germany, in a statement. "I like to imagine that on some of these worlds, the sky is filled not only with stars but also with vast curtains of colorful light, dancing across a planet that is half immersed in eternal day and half in endless night.".
The team's findings were published Tuesday (June 2) in the journal Nature Astronomy.