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
Peer-Reviewed PublicationIMAGE: ARTIST’S IMPRESSION OF AN AURORA AND THE SURROUNDING RADIATION BELT OF THE ULTRACOOL DWARF LSR J1835+3259. view more
CREDIT: IMAGE CREDIT: CHUCK CARTER, MELODIE KAO, HEISING-SIMONS FOUNDATION
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 15 in 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.
The first images of an extrasolar radiation belt were obtained by combining 39 radio telescopes to form a virtual telescope spanning the globe from Hawaii to Germany.
The electron radiation belt and aurora of an ultracool dwarf were imaged by combining 39 radio telescopes to form a virtual telescope spanning the globe from Hawaii to Germany.
The electron radiation belt and aurora of an ultracool dwarf were imaged by combining 39 radio telescopes to form a virtual telescope spanning the globe from Hawaii to Germany.
CREDIT
Image credit: Melodie Kao, Amy Mioduszewsk
Image credit: Melodie Kao, Amy Mioduszewsk
JOURNAL
Nature
ARTICLE TITLE
Resolved imaging confirms a radiation belt around an ultracool dwarf
ARTICLE PUBLICATION DATE
15-May-2023
Latest research provides SwRI scientists close-up views of energetic particle jets ejected from the Sun
New study observes unusual isotope variations in solar particle injections
Business AnnouncementIMAGE: SOUTHWEST RESEARCH INSTITUTE (SWRI) SCIENTISTS OBSERVED THE FIRST CLOSE-UP VIEWS OF THE SOURCE OF JETS OF ENERGETIC PARTICLES EXPELLED FROM THE SUN. THE HIGH-RESOLUTION IMAGES OF THE SOLAR EVENT WERE PROVIDED BY ESA AND NASA’S SOLAR ORBITER, A SUN-OBSERVING SATELLITE LAUNCHED IN 2020. view more
CREDIT: SOUTHWEST RESEARCH INSTITUTE
SAN ANTONIO — May 15, 2023 —Southwest Research Institute (SwRI) scientists observed the first close-ups of a source of energetic particles expelled from the Sun, viewing them from just half an astronomical unit (AU), or about 46.5 million miles. The high-resolution images of the solar event were provided by ESA’s Solar Orbiter, a Sun-observing satellite launched in 2020.
“In 2022, the Solar Orbiter detected six recurrent energetic ion injections. Particles emanated along the jets, a signature of magnetic reconnection involving field lines open to interplanetary space,” said SwRI’s Dr. Radoslav Bucik, the lead author of a new study published this month in Astronomy & Astrophysics Letters. “The Solar Orbiter frequently detects this type of activity, but this period showed very unusual elemental compositions.”
In one ion injection, the intensity of the rare isotope Helium-3 exceeded the amount of hydrogen, the most abundant element on the Sun, and the levels of iron were similar to the isotope Helium-4, the second most abundant element on the Sun. In another injection two days later, the amount of Helium-3 had significantly decreased to an almost negligible amount.
“Our analysis shows that the elemental and spectral variations in recurrent injections are associated with the shape of the jet, the size of the jet source and the distribution of the underlying photospheric field that evolved over time,” Bucik said. “We believe that understanding the variability in recurrent events from a single source sheds light on the acceleration mechanism in solar flares.”
The observations made by Solar Orbiter are unique as the propagation effects that can affect abundances could be minimal near the Sun. The distance of just 0.5 AU has given the scientific team a remarkably detailed view of solar events.
“When we are closer, we have a considerably better spatial resolution,” Bucik said. “We are able to gain more insight into the source of these energetic particles because we can see the internal structure associated with acceleration processes as the injection evolves. Observations from twice that distance, 1 AU, are not very clear in comparison.”
Bucik and his colleagues hope to learn even more from the Solar Orbiter’s closest approaches to the Sun at 0.3 AU.
“These observations could help predict future solar energetic particle events,” Bucik said. “These particles can damage satellites and equipment and potentially harm astronauts. We want to understand how they accelerate away from the Sun and what the conditions are for their acceleration.”
The paper “Recurrent 3He-rich solar energetic particle injections observed by Solar Orbiter at ~0.5 au,” appears in Astronomy & Astrophysics (Letters to the Editor): https://www.aanda.org/component/article?access=doi&doi=10.1051/0004-6361/202345875
For more information, visit https://www.swri.org/heliophysics.
METHOD OF RESEARCH
Observational study
New deal inked to space test meta-optical surfaces
European Space Agency funds project
Business AnnouncementIMAGE: TMOS CENTRE DIRECTOR DRAGOMIR NESHEV AND LABORAXPERT CEO VESSELIN VASSILEV SIGN A NEW DEAL TO SPACE-TEST METASURFACES IN A FIRST-OF-ITS-KIND STUDY. view more
CREDIT: SAMARA THORN
A new engineering study has been commissioned by the European Space Agency (under PECS, the Program for European Cooperating States), to prove the reliability of meta-optical elements for space use in a collaboration between the ESA, Bulgarian start-up company LaboraXpert and TMOS, the Australian Research Council Centre of Excellence for Transformative Meta-Optical Systems.
In the first study of its kind, it will determine whether meta-optical components can withstand the pressures of space launch and prolonged exposure to the space environment.
TMOS Centre Director Prof. Dragomir Neshev says, “The demand for Earth observation data is growing, yet the industry still faces the challenge of size and weight constraints when sending a payload into space. Meta-optics will allow for the simultaneous advancement of the functionality and miniaturization of remote sensing systems. This study will provide information towards the development of robust space applications using meta-material optical elements.”
LaboraXpert’s CEO, Dr. Vesselin Vassilev, says, “Space is a booming industry that relies on developing advanced technologies and solutions in various domains. It offers a great opportunity to demonstrate the performance of the advanced imaging systems our company is developing. TMOS’s research goals align closely with our company’s determination to provide ground breaking multi-spectral sensors for space and other applications. We hope this is the first step of a longer term applied R&D collaboration.”
Prof. Neshev says, “We believe meta-optics will enable a new set of innovative applications because of its ability to miniaturise complex optical devices and provide additional embedded functionality of optical systems. Meta-optics significantly outperforms bulky traditional optics in its low size, weight and power requirements, which will have a great benefit for the space industry. Space environment applications are tough ones to succeed in. This project with LaboraXpert and ESA is an indication of the quality cutting-edge technology TMOS is pioneering.”
Both Prof.Neshev and Dr. Vassilev hope this project foreshadows a deepening of advanced industry and research collaboration between Europe and Australia.
For more information about this project, please contact connect@tmos.org.au
METHOD OF RESEARCH
News article
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