MSGID: 1:317/3 646306ee   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Astronomers observe the first radiation belt seen outside of our solar   
   system    
    High-resolution imaging of radio emissions from an ultracool dwarf show a   
   double-lobed structure like the radiation belts of Jupiter    
      
     Date:   
         May 15, 2023   
     Source:   
         University of California - Santa Cruz   
     Summary:   
         Astronomers have described the first radiation belt observed outside   
         our solar system, using a coordinated array of 39 radio dishes from   
         Hawaii to Germany to obtain high-resolution images. The images   
         of persistent, intense radio emissions from an ultracool dwarf   
         reveal the presence of a cloud of high-energy electrons trapped   
         in the object's powerful magnetic field, forming a double-lobed   
         structure analogous to radio images of Jupiter's radiation belts.   
      
      
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   FULL STORY   
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   Astronomers have described the first radiation belt observed outside our   
   solar system, using a coordinated array of 39 radio dishes from Hawaii   
   to Germany to obtain high-resolution images. The images of persistent,   
   intense radio emissions from an ultracool dwarf reveal the presence of a   
   cloud of high-energy electrons trapped in the object's powerful magnetic   
   field, forming a double- lobed structure analogous to radio images of   
   Jupiter's radiation belts.   
      
   "We are actually imaging the magnetosphere of our target by observing the   
   radio-emitting plasma -- its radiation belt -- in the magnetosphere. That   
   has never been done before for something the size of a gas giant planet   
   outside of our solar system," said Melodie Kao, a postdoctoral fellow at   
   UC Santa Cruz and first author of a paper on the new findings published   
   May 15in Nature.   
      
   Strong magnetic fields form a "magnetic bubble" around a planet called a   
   magnetosphere, which can trap and accelerate particles to near the speed   
   of light. All the planets in our solar system that have such magnetic   
   fields, including Earth, as well as Jupiter and the other giant planets,   
   have radiation belts consisting of these high-energy charged particles   
   trapped by the planet's magnetic field.   
      
   Earth's radiation belts, known as the Van Allen belts, are large   
   donut-shaped zones of high-energy particles captured from solar winds   
   by the magnetic field.   
      
   Most of the particles in Jupiter's belts are from volcanoes on its moon   
   Io. If you could put them side by side, the radiation belt that Kao and   
   her team have imaged would be 10 million times brighter than Jupiter's.   
      
   Particles deflected by the magnetic field toward the poles generate   
   auroras ("northern lights") when they interact with the atmosphere,   
   and Kao's team also obtained the first image capable of differentiating   
   between the location of an object's aurora and its radiation belts   
   outside our solar system.   
      
   The ultracool dwarf imaged in this study straddles the boundary between   
   low- mass stars and massive brown dwarfs. "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 explained.   
      
   Characterizing the strength and shape of the magnetic fields of this class   
   of objects is largely uncharted terrain, she said. Using their theoretical   
   understanding of these systems and numerical models, planetary scientists   
   can predict the strength and shape of a planet's magnetic field, but   
   they haven't had a good way to easily test those predictions.   
      
   "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.   
      
   The strength and shape of the magnetic field can be an important factor   
   in determining a planet's habitability. "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," Kao said.   
      
   To generate a magnetic field, a planet's interior must be hot enough to   
   have electrically conducting fluids, which in the case of Earth is the   
   molten iron in its core. In Jupiter, the conducting fluid is hydrogen   
   under so much pressure it becomes metallic. Metallic hydrogen probably   
   also generates magnetic fields in brown dwarfs, Kao said, while in the   
   interiors of stars the conducting fluid is ionized hydrogen.   
      
   The ultracool dwarf known as LSR J1835+3259 was the only object Kao   
   felt confident would yield the high-quality data needed to resolve its   
   radiation belts.   
      
   "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," Kao said, adding that   
   she is looking forward to when the Next Generation Very Large Array,   
   currently being planned by the National Radio Astronomy Observatory   
   (NRAO), can image many more extrasolar radiation belts.   
      
   "This is a critical first step in finding many more such objects and   
   honing our skills to search for smaller and smaller magnetospheres,   
   eventually enabling us to study those of potentially habitable, Earth-size   
   planets," said coauthor Evgenya Shkolnik at Arizona State University,   
   who has been studying the magnetic fields and habitability of planets   
   for many years.   
      
   The team used the High Sensitivity Array, consisting of 39 radio dishes   
   coordinated by the NRAO in the United States and the Effelsberg radio   
   telescope operated by the Max Planck Institute for Radio Astronomy   
   in Germany.   
      
   "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.," said coauthor Jackie Villadsen at   
   Bucknell University.   
      
   Kao emphasized that this discovery was a true team effort, relying heavily   
   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.   
      
       * RELATED_TOPICS   
             o Space_&_Time   
                   # Solar_Flare # Sun # Extrasolar_Planets # Stars #   
                   Jupiter # Solar_System # Cosmic_Rays # Eris_(Xena)   
       * RELATED_TERMS   
             o Radio_telescope o Solar_flare o Ionosphere o   
             Van_Allen_radiation_belt o Solar_system o Geomagnetic_reversal   
             o Spitzer_space_telescope o Green_Bank_Telescope   
      
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   Story Source: Materials provided by   
   University_of_California_-_Santa_Cruz. Original written by Tim   
   Stephens. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Melodie M. Kao, Amy J. Mioduszewski, Jackie Villadsen, Evgenya L.   
      
         Shkolnik. Resolved imaging confirms a radiation belt around an   
         ultracool dwarf. Nature, 2023; DOI: 10.1038/s41586-023-06138-w   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/05/230515131947.htm   
      
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