Earth has one. So do Jupiter, Saturn, and Uranus. Mars and Venus, on the other hand, don't have a global version of it. We're talking about magnetic fields — invisible force fields generated deep inside some planets by the movement of electrically conducting material.
On Earth, this magnetic shield does much more than create dazzling auroras. It also helps protect our atmosphere from harmful radiation, making the planet a friendlier place for life.
Finding magnetic fields beyond our Solar System, however, has proven extremely difficult. Initially planning to measure the wind speeds on a group of distant planets, astronomers stumbled upon an odd anomaly that hinted at the presence of magnetic fields.
As described in their Nature Astronomy study, this is the first strong estimate of magnetic field strengths for seven so-called ultra-hot Jupiters, which are giant gas planets that orbit extremely close to their stars. The findings suggest that some of these alien worlds possess magnetic fields comparable to those of planets in our own Solar System.
“This breakthrough opens a completely new window on exoplanet research,” said study lead author and astronomer Julia Seidel in a press statement. “It’s the first time we can compare the magnetic environments of other worlds — a key step toward ultimately understanding which planets can stay alive, keep their water, and perhaps even, one day, host life as we know it.”
Read more: James Webb Space Telescope Captures Smallest Exoplanet Ever Seen in Historic First
Chasing Winds on Exoplanets
The Gemini North telescope
(Image Credit: International Gemini Observatory/NOIRLab/NSF/AURA/J. Chu/J. Pollard/ CCBY)
The researchers originally set out to study atmospheric winds, not magnetic fields. Their targets were seven ultra-hot Jupiters that always show the same face to their stars, much like the moon always shows the same side to Earth. This creates a blazing-hot day side and a much colder night side, driving extreme weather patterns.
The team measured winds ranging from roughly 4,400 to more than 15,500 miles per hour, numbers far faster than the strongest winds observed on Jupiter.
To take these measurements, the scientists used the MAROON-X instrument on the Gemini North telescope in Hawaiʻi, along with the ESPRESSO instrument on the European Southern Observatory's Very Large Telescope in Chile. By tracking the signatures of chemicals in the planets' atmospheres, they were able to determine how fast the gases were moving.
Slower Winds Hint at Magnetism
When the team compared wind speeds with planetary temperatures, they found something unexpected: the hottest planets had slower winds.
“This is totally counterintuitive 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,” said study co-author Vivien Parmentier, a professor at the Laboratoire Lagrange, in the release.
The most likely explanation, the researchers argue, is magnetism. Strong magnetic fields can interact with charged particles in an atmosphere and effectively put the brakes on atmospheric motion.
Using this relationship, the team estimated the strength of each planet's magnetic field. The results suggest fields roughly four times stronger than Saturn's or about half as strong as Jupiter's.
Magnetic Fields Help Shape Atmospheres
“The unexpected discovery that resulted from studying the winds of these seven ultra-hot Jupiters shows that there is even more that we can learn from the data,” explained study co-author Andreas Seifahrt, associate director of the Gemini Observatory, in the statement.
Besides slowing down winds, strong magnetic fields could also produce spectacular auroras.
“Here on Earth, we know the beauty of the northern and southern lights, where particles from the sun hit our magnetic field and are guided toward the poles, colliding with gases in the atmosphere to produce [colorful] displays of green, pink, and purple,” said study co-author Bibiana Prinoth, astronomer at ESO in Garching, Germany, in the release.
Beyond creating dramatic light shows, magnetic fields play an important role in shaping planetary atmospheres over time. The new findings provide some of the strongest evidence yet that magnetism influences weather on ultra-hot Jupiters and could help scientists estimate magnetic fields on many other exoplanets, including rocky worlds that may resemble Earth.
Read More: Gigantic Hot Rock Blobs Have Impacted Earth's Magnetic Field For Over 200 Million Years
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Nature Astronomy: Magnetic field strengths of hot giant exoplanets consistent with Solar System values
