Radiation Belt Seen Beyond the Solar System for the First Time

Imaging revealed the presence of a cloud of high-energy electrons trapped in the magnetic field of the dwarf star, which is known as LSR J1835+3259.

Astronomers have observed a radiation belt outside the solar system for the first time, imaging high-energy particles trapped by a magnetic field around an ultra-cool dwarf star around 18 light-years from Earth.

The newfound radiation belt is double-lobed, just like the radiation belts that encircle Jupiter, the largest planet in the solar system. But if the dwarf star's radiation belt were placed next to that of Jupiter, it would be 10 million times brighter.

The radiation is in the form of persistent, intense radio emissions. Imaging revealed the presence of a cloud of high-energy electrons trapped in the magnetic field of the dwarf star, which is known as LSR J1835+3259.

Melodie Kao’s statement

"We are actually imaging the magnetosphere of our target by observing the radio-emitting plasma—  its radiation belt  —  in the magnetosphere," research lead author and University of California, Santa Cruz postdoctoral fellow Melodie Kao said in a statement (opens in a new tab). "That has never been done before for something the size of a gas giant planet outside of our solar system."

"While the formation of stars and planets can be different, the physics inside of them can be very similar in that mushy part of the mass continuum connecting low-mass stars to brown dwarfs and gas giant planets," Kao said.

Insights about the image

The image was captured by the team using a network of 39 radio telescopes, which combined to form a single virtual telescope called the High Sensitivity Array.

LSR J1835+3259 was the only object beyond the solar system that Kao was confident could be observed with enough detail to resolve its radiation belts. And, because the dwarf star has a mass that lies between low-mass stars and brown dwarfs — objects often referred to as "failed stars" because they lack the mass needed to initiate nuclear fusion at their cores — the new observations could help astronomers find the dividing line between small stars and large planets.

Observing an extrasolar aurora

Strong magnetic fields form a magnetic bubble around a planet called a magnetosphere, which can trap and accelerate charged particles to speeds approaching those of light. Many planets in the solar system have magnetospheres, as does the sun. Even one solar system moon — the huge Jovian satellite Ganymede—  has a magnetosphere.