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This artist's concept depicts a magnetar losing material into space, potentially causing a slowdown in its rotation. The strong, twisted magnetic field lines (depicted in green) of the magnetar play a key role in influencing the flow of electrically charged material from this type of neutron star. |
Researchers, utilizing two of NASA's X-ray telescopes, closely observed the erratic behavior of a dead star, capturing a vivid moment when it emitted a bright and brief burst of radio waves. This groundbreaking observation provides astronomers with a unique window into the occurrence of fast radio bursts, shedding light on these mysterious events from deep space. The telescopes recorded the event just minutes before and after its happening, offering unprecedented insights. Despite lasting only a fraction of a second, fast radio bursts release energy equivalent to the Sun's annual output and exhibit a distinctive laserlike beam, distinguishing them from other cosmic explosions.
The challenge of pinpointing the origins of fast radio bursts due to their brief nature changed in 2020 when one was traced within our own galaxy. This specific burst emanated from a magnetar, the remnants of a collapsed star, named SGR 1935+2154. In October 2022, this magnetar produced another fast radio burst, extensively studied by NASA's NICER (Neutron Star Interior Composition Explorer) on the International Space Station and NuSTAR (Nuclear Spectroscopic Telescope Array) in low Earth orbit.
The telescopes observed SGR 1935+2154 for hours, providing insights into events occurring on its surface and immediate surroundings before and after the fast radio burst. This collaborative effort, outlined in a recent study published on Feb. 14 in the journal Nature, exemplifies how NASA telescopes can collaboratively capture and investigate transient cosmic events.
The fast radio burst observed from SGR 1935+2154 occurred between two instances of "glitches," marked by sudden increases in the magnetar's spinning speed. With an estimated diameter of about 12 miles (20 kilometers) and a rotational frequency of approximately 3.2 times per second, equivalent to a surface speed of 7,000 mph (11,000 kph), the magnetar's energy requirements for altering its rotation are substantial. Surprisingly, the study found that, in the nine hours between glitches, SGR 1935+2154 decelerated to below its pre-glitch speed – a phenomenon occurring about 100 times more rapidly than previously observed in magnetars.
This discovery challenges conventional understanding, suggesting that events with these objects unfold on much shorter timescales than previously thought, potentially holding clues to the rapid generation of fast radio bursts. Chin-Ping Hu, an astrophysicist at National Changhua University of Education in Taiwan, and the lead author of the study, emphasized the significance of these shorter timescales in understanding the magnetar's behavior and its connection to fast radio bursts.
Spin Cycle: Unraveling the Mystery of Magnetar's Fast Radio Burst and Glitches.
Understanding how magnetars generate fast radio bursts involves navigating a complex interplay of various factors. Magnetars, a subtype of neutron stars, exhibit an extraordinary density, with a mere teaspoon of their material weighing about a billion tons on Earth. This density corresponds to an immense gravitational pull; for instance, a marshmallow falling onto a typical neutron star would collide with the force akin to an early atomic bomb.
The intense gravity creates a volatile surface on a magnetar, causing frequent releases of X-rays and higher-energy light. Preceding the 2022 fast radio burst event, the magnetar exhibited eruptions of X-rays and gamma rays, even more energetic wavelengths, detected on the periphery of high-energy space telescopes. The heightened activity prompted mission operators to reposition NICER and NuSTAR, focusing directly on the magnetar to capture and analyze the unfolding phenomena. The intricate dynamics of magnetars pose a fascinating puzzle for scientists seeking to unravel the origins of fast radio bursts.
Zorawar Wadiasingh, a research scientist at the University of Maryland, College Park, and NASA’s Goddard Space Flight Center, noted that despite the substantial energy in the X-ray bursts preceding the glitch, they didn't trigger a fast radio burst from SGR 1935+2154. The slowdown period, however, introduced changes creating the right conditions for the subsequent fast radio burst. One potential factor is the solid exterior of magnetars, with their high density causing the interior to become a superfluid. If the exterior and superfluid get out of sync, it can release energy to the crust, potentially causing glitches and, in this case, a fast radio burst.
The researchers suggest that the initial glitch may have caused a surface crack, leading to a volcanic-like eruption expelling material into space. The loss of mass in such an event could explain the magnetar's rapid deceleration. However, with only one observed event, uncertainties remain about which factors, such as the magnetar's powerful magnetic field, contribute to fast radio burst production. George Younes, a researcher at Goddard and a member of the NICER science team specializing in magnetars, emphasized the importance of the observation for understanding fast radio bursts but highlighted the need for more data to fully unravel the mystery.
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