Ultracool dwarf reveals Jupiter-like radiation belts in high-resolution imaging

Using a network of 39 radio dishes spanning from Hawaii to Germany, astronomers have detected the first radiation belt ever observed beyond our solar system. By capturing high-resolution images of persistent and powerful radio emissions emanating from an ultracool dwarf, known as LSR J1835+3259, they were able to identify the existence of a group of high-energy electrons confined within the object's powerful magnetic field. The resulting double-lobed structure is reminiscent of the radio images of Jupiter's radiation belts.

A planet's magnetosphere, created by strong magnetic fields, can trap and accelerate particles to near the speed of light. In our solar system, all planets possessing such magnetic fields, such as Earth, Jupiter, and the other gas giants, have radiation belts comprised of high-energy charged particles that are trapped by the planet's magnetic field.

Earth's radiation belts are large donut-shaped zones of high-energy particles captured from solar winds by the magnetic field. In the case of Jupiter, the majority of particles within its belts originate from the volcanic activity on its moon Io. Comparing the two, the radiation belt captured in the new image would exhibit a brightness 10 million times greater than that of Jupiter's if they were placed side by side.

When particles are diverted towards the poles by the magnetic field, their interaction with the atmosphere gives rise to captivating auroras, commonly referred to as northern lights.

The team, led by Melodie Kao, a postdoctoral fellow at UC Santa Cruz, also obtained the first image capable of differentiating between the location of an object's aurora and its radiation belts outside our solar system.

"Auroras can be used to measure the strength of the magnetic field, but not the shape. We designed this experiment to showcase a method for assessing the shapes of magnetic fields on brown dwarfs and eventually exoplanets," Kao said.

This discovery was made using the High Sensitivity Array, a collection of 39 radio dishes coordinated by the NRAO (National Radio Astronomy Observatory) in the United States, along with the Effelsberg radio telescope, which is operated by the Max Planck Institute for Radio Astronomy in Germany.