Astronomers Detect Gamma-Ray Burst’s Magnetic Fingerprint

Using NSF’s Very Large Array (VLA), astronomers made the first radio detection of polarized light and Faraday rotation from a gamma-ray burst afterglow, offering an unprecedented glimpse of the magnetic fields surrounding one of the Universe’s most powerful explosions.

This illustration depicts Faraday rotation in the afterglow of a gamma-ray burst. A powerful jet (upper left) sends polarized radio waves outward through the thin wall of a surrounding bubble of magnetized gas called an HII region. As the light passes through this material, its polarization angle is twisted by the magnetic field. Because the effect is stronger at longer wavelengths, the red and blue waves, which represent different radio wavelengths, exit the bubble oscillating in different directions. By measuring this difference, astronomers were able to map the magnetic environment surrounding GRB 260310A for the first time. Image credit: NSF / AUI / NRAO / M. Weiss