Did you know that Earth is a giant magnet? Just like the smaller magnets you might have played with, an invisible magnetic field surrounds our planet. It acts like a shield, stopping the layer of gases around Earth, called the atmosphere, from being blown away by powerful streams of particles emitted by the Sun! Our atmosphere is essential for life on Earth, and the planet’s magnetic field protects this.
But what about planets outside our Solar System? Could they have magnetic fields? Could that help extra-Solar planets (so-called “exoplanets”) host life? For the first time, a team of astronomers has measured the magnetic fields of exoplanets. It all started when they noticed a strange trend in a group of distant worlds.
The team was trying to measure the wind speeds of seven different exoplanets, all gas giants like Jupiter, that orbit very close to their stars. Unlike Earth, which completes 365 rotations on its year-long trip around the Sun, these exoplanets only complete one rotation per round trip, always keeping the same side facing their star. This creates a permanent, scorching-hot dayside and a freezing-cold nightside! The huge temperature difference between the two sides of these planets creates super-strong winds in their atmospheres. The fastest wind speed they measured was over 25 000 kilometres per hour, almost as quick as the International Space Station as it flies around Earth!
Using ESO’s Very Large Telescope (VLT) and the US National Science Foundation’s Gemini North telescope, astronomers focused in on the planets’ atmospheres to see how their wind speed changed with planet temperature. They expected the hotter planets to have the fastest winds because they had more energy, but they found the opposite was true: the hotter planets had slower winds instead!
The best explanation the team found for this unusual trend is that each planet has a magnetic field, like Earth does. The magnetic field acts like a brake on the wind, slowing it down. The hotter the planet, the stronger its magnetic field, and so the more the wind gets slowed down. The team worked out that the magnetic fields for these planets are much stronger than Earth’s and are more similar to the magnetic fields of Jupiter and Saturn, planets farther out in our Solar System. Their discovery is the strongest evidence yet that exoplanets can also be magnetic!
(Space Scoop)
