Researchers Detect Exceptionally Strong Magnetic Field on Exoplanet GJ 436 b Influencing Its Star
An international research team, including scientists from Tel Aviv University, has provided the strongest evidence yet of a powerful magnetic field on an exoplanet outside our solar system. The study, led by the Institute of Astrophysics of Andalusia (IAA-CSIC) and published in Science, focused on the Neptune-like planet GJ 436 b, which orbits very close to its host star. Over 16 years, researchers analyzed high-resolution spectroscopic observations and discovered periodic changes in the star's light emissions synchronized with the planet's orbit.
Professor Shay Zucker from Tel Aviv University explained that these cyclical variations demonstrate a direct magnetic interaction between GJ 436 b and its star, marking the most convincing proof to date of an exoplanet influencing its star's magnetic activity. This discovery enhances understanding of star-planet interactions and offers a new method to study magnetic fields on distant worlds.
Magnetic fields are crucial for protecting planetary atmospheres and potentially supporting life, as seen on Earth where the magnetic field shields the atmosphere from solar wind. By comparing observations with theoretical models, the team estimated that GJ 436 b's magnetic field strength ranges from 2.3 to 27 times that of Jupiter, the strongest magnetic field in our solar system. The planet's magnetic field interacts with the star's field, energizing its upper atmosphere and producing phenomena akin to Earth's auroras but on a stellar scale.
Interestingly, this interaction was observed only during three events in 2008, 2016, and 2024, likely linked to the star's magnetic activity cycle. The researchers suggest that the interaction's detectability varies with the star's magnetic phases.
This breakthrough opens new avenues for measuring exoplanetary magnetic fields, which were previously nearly impossible to detect. It could help scientists understand how exoplanets retain their atmospheres, reveal their internal structures, and better assess their potential habitability. Professor Zucker emphasized that detecting a planet's magnetic fingerprint through its star's activity is a significant advancement for exploring distant worlds and the conditions necessary for life.
