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First Exosolar Radiation Belt Identified

exosolar radiation belt

Astronomers have made an unprecedented discovery: the first-ever radiation belt beyond the confines of our solar system.

Astronomers have made an unprecedented discovery: the first-ever radiation belt beyond the confines of our solar system. Utilizing a coordinated network of 39 radio telescopes spanning from Hawaii to Germany, they captured high-resolution images of radio emissions from an ultracool dwarf. The emissions revealed a cloud of high-energy electrons trapped in a powerful magnetic field, forming a structure akin to Jupiter’s radiation belts.

Imagining the Unseen: Magnetospheres Beyond Our Reach

UC Santa Cruz postdoctoral fellow Melodie Kao, the first author of the findings published in Nature, said, “We’re essentially imaging the magnetosphere of our target by observing the radio-emitting plasma—its radiation belt—in the magnetosphere. That’s a first for a gas giant-sized object outside our solar system.”

The Physics of Magnetic Bubbles and Speeding Particles

Strong magnetic fields form a protective ‘magnetic bubble’ around a planet, known as a magnetosphere. These fields can trap and speed up particles near light speed. Earth, Jupiter, and other planets with such fields possess radiation belts filled with these high-energy particles. Earth’s Van Allen belts and Jupiter’s belts are examples of these zones.

A Bright New Star in Radiation Belts

Kao and her team revealed that the newly discovered radiation belt would outshine Jupiter’s belt by 10 million times if placed side by side. The team also managed to distinguish between the object’s aurora and its radiation belt locations, another first beyond our solar system.

The Bridge Between Stars and Massive Brown Dwarfs

The ultracool dwarf in the study lies on the cusp of low-mass stars and massive brown dwarfs. Kao elaborated, “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.”

Uncharted Magnetic Fields and Planet Habitability

Assessing the strength and shape of magnetic fields in such objects is largely unexplored, according to Kao. These fields can play a vital role in determining a planet’s habitability. Kao said, “When we’re thinking about the habitability of exoplanets, the role of their magnetic fields in maintaining a stable environment is something to consider in addition to things like the atmosphere and climate.”

The Ultracool Dwarf LSR J1835+3259: A Radiation Belt Revealed

The ultracool dwarf known as LSR J1835+3259 was the only object Kao felt would provide the high-quality data required to resolve its radiation belts. She stated, “Now that we’ve established that this particular kind of steady-state, low-level radio emission traces radiation belts in the large-scale magnetic fields of these objects, when we see that kind of emission from brown dwarfs—and eventually from gas giant exoplanets—we can more confidently say they probably have a big magnetic field, even if our telescope isn’t big enough to see the shape of it.”

The Future: Uncovering More Extrasolar Radiation Belts

The team looks forward to when the Next Generation Very Large Array, currently being planned by the National Radio Astronomy Observatory (NRAO), can image more extrasolar radiation belts. Coauthor Evgenya Shkolnik at Arizona State University remarked, “This is a crucial initial step in discovering many more such objects and refining our skills to search for smaller and smaller magnetospheres, eventually enabling us to study those of potentially habitable, Earth-sized planets.”

The High Sensitivity Array: A Global Effort

The High Sensitivity Array was used for the study, a combination of 39 radio dishes coordinated by the NRAO in the U.S. and the Effelsberg radio telescope operated by Germany’s Max Planck Institute for Radio Astronomy.

Coauthor Jackie Villadsen at Bucknell University stated, “By combining radio dishes from across the world, we can make incredibly high-resolution images to see things no one has ever seen before. Our image is comparable to reading the top row of an eye chart in California while standing in Washington, D.C.”

The Power of Collaboration and Future Prospects

Kao emphasized that this discovery was a collective achievement, reliant on the observational expertise of co-first author Amy Mioduszewski at NRAO in planning the study and analyzing the data, as well as the multiwavelength stellar flare expertise of Villadsen and Shkolnik. This work was supported by NASA and the Heising-Simons Foundation.

The findings mark a significant step forward in our understanding of magnetic fields in space, potentially opening up new avenues of study in the search for habitable exoplanets and furthering our knowledge of the universe.

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  1. Kao, M. et al. (2023). First exosolar radiation belt discovered. Nature. Retrieved from Nature Website
  2. UC Santa Cruz. (2023). Groundbreaking radio imaging reveals first exosolar radiation belt. UC Santa Cruz Newscenter. Retrieved from UC Santa Cruz Newscenter Website
  3. Arizona State University. (2023). Exploring exoplanet magnetospheres for habitability. ASU News. Retrieved from ASU News Website
  4. Heising-Simons Foundation. (2023). Foundation-supported research uncovers first exosolar radiation belt. Heising-Simons Foundation News. Retrieved from Heising-Simons Foundation Website