SPACE/COSMOS
Astronomers thought they understood fast radio bursts. A recent one calls that into question.
The new ability to pinpoint sources of fast radio bursts places one recent burst in a surprising location
University of California - Berkeley
image:
The location of the fast radio burst, indicated by the oval outlines, is on the outskirts of a massive elliptical galaxy, the yellow oval at right.
view moreCredit: Gemini Observatory
Astronomer Calvin Leung was excited last summer to crunch data from a newly commissioned radio telescope to precisely pinpoint the origin of repeated bursts of intense radio waves — so-called fast radio bursts (FRBs) — emanating from somewhere in the northern constellation Ursa Minor.
Leung, a Miller Postdoctoral Fellowship recipient at the University of California, Berkeley, hopes eventually to understand the origins of these mysterious bursts and use them as probes to trace the large-scale structure of the universe, a key to its origin and evolution. He had written most of the computer code that allowed him and his colleagues to combine data from several telescopes to triangulate the position of a burst to within a hair's width at arm's length.
The excitement turned to perplexity when his collaborators on the Canadian Hydrogen Intensity Mapping Experiment (CHIME) turned optical telescopes on the spot and discovered that the source was in the distant outskirts of a long-dead elliptical galaxy that by all rights should not contain the kind of star thought to produce these bursts.
Instead of finding an expected "magnetar" — a highly magnetized, spinning neutron star left over from the core collapse of a young, massive star — "now the question was: How are you going to explain the presence of a magnetar inside this old, dead galaxy?" Leung said.
The young stellar remnants that theorists think produce these millisecond bursts of radio waves should have disappeared long ago in the 11.3-billion-year-old galaxy, located 2 billion light years from Earth and weighing more than 100 billion times the mass of the sun.
“This is not only the first FRB to be found outside a dead galaxy, but compared to all other FRBs, it’s also the farthest from the galaxy it’s associated with. The FRB’s location is surprising and raises questions about how such energetic events can occur in regions where no new stars are forming,” said Vishwangi Shah, a doctoral student at McGill University in Montreal, Canada, who refined and extended Leung's initial calculations about the location of the burst, called FRB 20240209A.
Shah is the corresponding author of a study of the FRB published today (Tuesday, Jan. 21) in the Astrophysical Journal Letters along with a second paper by colleagues at Northwestern University in Evanston, Illinois. Leung, a co-author of both papers, is a lead developer of three companion telescopes — so-called outriggers — to the original CHIME radio array located near Penticton, British Columbia. He mentored Shah at McGill while Leung was a doctoral student at the Massachusetts Institute of Technology (MIT) and subsequently held an Einstein Postdoctoral Fellowship at UC Berkeley prior to his Miller fellowship.
New CHIME outrigger in California
A third outrigger radio array will go online this week at Hat Creek Observatory, a facility in Northern California formerly owned and operated by UC Berkeley and now managed by the SETI Institute in Mountain View. Together, the four arrays will immensely improve CHIME's ability to precisely locate FRBs.
"When paired with the three outriggers, we should be able to accurately pinpoint one FRB a day to its galaxy, which is substantial," Leung said. "That's 20 times better than CHIME, with two outrigger arrays."
With this new precision, optical telescopes can pivot to identify the type of star groups — globular clusters, spiral galaxies — that produce the bursts and hopefully identify the stellar source. Of the 5,000 or so sources detected to date — over 95% of which were detected by CHIME — few have been isolated to a specific galaxy, which has hindered efforts to confirm whether magnetars or any other type of star are the source.
As detailed in the new paper, Shah averaged many bursts from the repeating FRB to improve the pinpointing accuracy provided by the CHIME array and one outrigger array in British Columbia. After its discovery in February 2024, astronomers recorded 21 more bursts through July 31. Since the paper was submitted, Shion Andrew at MIT incorporated data from a second outrigger at the Green Bank Observatory in West Virginia to confirm Shah's published position with 20 times the precision.
“This result challenges existing theories that tie FRB origins to phenomena in star-forming galaxies,” said Shah. “The source could be in a globular cluster, a dense region of old, dead stars outside the galaxy. If confirmed, it would make FRB 20240209A only the second FRB linked to a globular cluster.”
She noted, however, that the other FRB originating in a globular cluster was associated with a live galaxy, not an old elliptical in which star formation ceased billions of years ago.
“It's clear that there's still a lot of exciting discovery space when it comes to FRBs and that their environments could hold the key to unlocking their secrets,” said Tarraneh Eftekhari, who has an Einstein Postdoctoral Fellowship at Northwestern and first author of the second paper.
"CHIME and its outrigger telescopes will let us do astrometry at a level unmatched by the Hubble Space Telescope or the James Webb Space Telescope. It'll be up to them to drill down to find the source," Leung added. "It's an amazing radio telescope."
The studies were supported by Gordon and Betty Moore Foundation, NASA, the Space Telescope Science Institute, the National Science Foundation, the David and Lucile Packard Foundation, the Alfred P. Sloan Foundation, the Research Corporation for Science Advancement, the Canadian Institute for Advanced Research, the Natural Sciences and Engineering Council of Canada, the Canada Foundation for Innovation and the Trottier Space Institute at McGill.
Journal
The Astrophysical Journal Letters
Article Title
A Repeating Fast Radio Burst Source in the Outskirts of a Quiescent Galaxy
Article Publication Date
21-Jan-2025
NASA rockets to fly through flickering, vanishing auroras
NASA/Goddard Space Flight Center
Two NASA rocket missions are taking to the Alaskan skies in hopes of discovering why some auroras flicker, others pulsate, and still others are riddled with holes. Understanding these peculiar features is part of NASA’s goal to understand the space environment around our planet, which can affect both spacecraft and astronauts. The launch window for the missions — which will fly out of the Poker Flat Research Range in Fairbanks, Alaska — opens on Jan. 21, 2025.
Witnessing the aurora borealis, or northern lights, can be a moving experience. As ribbons of color fill the night sky, Earth’s ever-present connection to space is made visually manifest. It can quiet the mind. Yet these serenity-inducing shimmers are sustained by countless tiny collisions, cascades of little crashes, each perpetrated by a wayward electron. They leave gases glowing in their aftermath like smoldering wreckage. For those less romantically inclined, aurora-watching might be considered top-notch rubbernecking.
This metaphor for the aurora is slightly dramatic. But it does highlight the question that Marilia Samara and Robert Michell, both space physicists at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, are after: What sends these electrons careening off course? Like crime scene investigators, Samara and Michell will use clues at the crash site and work backward to investigate the cause. As principal investigators of the two soon-to-launch rocket missions, they plan to fly rockets through active auroras to reveal what sent them on their distructive courses.
The GIRAFF (Ground Imaging to Rocket investigation of Auroral Fast Features) mission comprises two rockets, each carrying the same set of instruments. Each rocket will target a distinct subtype of aurora: one for so-called fast-pulsating auroras, which flash on and off a few times a second, and the other for flickering auroras, which do so up to 15 times a second.
“It looks like the flickering of an old TV,” Michell, who leads the GIRAFF mission, said.
Michell suspects that fast-pulsating versus flickering auroras are fueled by different electron acceleration processes. To find out, his team will launch one rocket into each type of aurora, measuring the energy, quantity, and relative arrival times of the electron populations forming them. The measurements, he hopes, may reveal which acceleration processes are at work and constrain where in near-Earth space they are occurring.
The second rocket mission, led by Samara, will study so-called “black auroras,” where light from an aurora appears to be missing. In the last 25 years, research using the ESA (European Space Agency) and NASA Cluster satellites has hinted that these dark spots may form where the normally incoming stream of electrons reverses direction, escaping back out into space. Of course, not every blank spot in the aurora fits this description. You need to detect outgoing electrons to know it’s the real deal.
“Otherwise that’s not black aurora, it is just the lack of aurora,” said Samara.
Samara’s team will launch their rocket through the black aurora and surrounding regions, surveying the electron populations as they fly through to understand how and why this stream reversal takes place. The mission is called the Black and Diffuse Aurora Science Surveyor. (Its acronym will be left as an exercise to the reader.)
‘The Hardest Part is Still Ahead’
Even in Alaska, where auroras shine most winter nights, flying a rocket through them is no small feat. Above terrestrial winds, the aurora move according to their own principles. To know when to launch, both teams will track the auroras via ground-based cameras at the launch site and at the down-range observatory in Venetie, Alaska, about 130 miles to the northeast along the rockets’ trajectory.
“We’ll be watching these structures moving in the all-sky camera, trying to time it just right,” Michell said.
Since it takes about five minutes to get the rockets to altitude, the teams must aim them not where the auroras are but where they think they will be. Of the many tools at their disposal, experience is the truest guide.
“You do the best you can, but there’s a certain mix of intuition and determination you need,” Samara said.
NASA’s Goddard Space Flight Center, Greenbelt, Md.
Method of Research
Experimental study
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