Researchers were able to focus on a dead star’s unpredictable behavior as it produced a dazzling, fleeting burst of radio waves by using two of the agency’s X-ray telescopes.

Mysterious radio wave bursts from outer space: what’s the cause? We might be getting closer to offering one answer to that query as astronomers. One such occurrence, called a rapid radio burst, was recently seen by two NASA X-ray telescopes just minutes before and after it happened. With the help of this novel perspective, scientists may now better comprehend these severe radio occurrences.

Fast radio bursts, though brief, can discharge almost the same amount of energy in a year as the Sun does. They can be distinguished from more chaotic cosmic explosions by the laser-like beam that their light produces.

The Origin of Rapid Radio Shocks

The bursts are so short-lived that locating their source is frequently challenging. The ones that could be tracked back to their source before 2020 came from beyond our galaxy, too far away for astronomers to see what produced them. Then, in the Milky Way, a quick radio burst occurred, coming from a very dense object known as a magnetar, which is the collapsed remnant of an exploding star.

Recognizing Magnetar Behavior

The same magnetar, known as SGR 1935+2154, produced another quick radio burst in October 2022. This one was thoroughly examined by NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) in low Earth orbit and NICER (Neutron Star Interior Composition Explorer) on the International Space Station. For hours, the magnetar was studied by telescopes to get a glimpse of the events that occurred on the surface of the source object and in the vicinity of it before to and during the rapid radio burst. The findings, which were detailed in a recent paper that was published on February 14 in the journal Nature, show how NASA telescopes can cooperate to monitor and track transient cosmic phenomena.

The burst happened when the magnetar abruptly began spinning faster, in between two “glitches.” With an estimated diameter of 12 miles (20 km) and a rotational speed of 3.2 x 10^9 rpm, SGR 1935+2154’s surface was travelling at approximately 7,000 mph (11,000 kph). A large quantity of energy would be needed to slow it down or accelerate it up. The magnetar slowed down to less than its pre-glitch speed in just nine hours, or around 100 times faster than has ever been seen in a magnetar, which is why the study’s authors were taken aback.

“Typically, when glitches happen, it takes the magnetar weeks or months to get back to its normal speed,” said Chin-Ping Hu, an astrophysicist at National Changhua University of Education in Taiwan and the lead author of the new study. “So clearly things are happening with these objects on much shorter time scales than we previously thought, and that might be related to how fast radio bursts are generated.”

Magnetar Physics

Scientists have many variables to take into account while attempting to put together the precise mechanism by which magnetars produce rapid radio bursts.

For instance, a teaspoon of the material in magnetars, a kind of neutron star, would weigh almost a billion tons on Earth due to their extreme density. An early atomic bomb would strike a normal neutron star with the force of a marshmallow due to its enormous density and strong gravitational attraction.

A magnetar’s surface is volatile due to its intense gravity, frequently unleashing bursts of higher-energy light and X-rays. The magnetar began erupting X-rays and gamma rays, which are even more energetic light wavelengths, before the fast radio burst that happened in 2022. These eruptions were visible in the periphery of high-energy satellite telescopes. The mission controllers decided to aim NICER and NuSTAR straight at the magnetar in response to this spike in activity.

“All those X-ray bursts that happened before this glitch would have had, in principle, enough energy to create a fast radio burst, but they didn’t,” said study co-author Zorawar Wadiasingh, a research scientist at the University of Maryland, College Park, and NASA’s Goddard Space Flight Center. “So it seems like something changed during the slowdown period, creating the right set of conditions.”

What other events may SGR 1935+2154 have had in order to cause a rapid radio burst? One explanation could be that a magnetar’s inside is crushed into a condition known as superfluid by the tremendous density, while the magnetar’s outside is solid. The two may occasionally drift apart, resembling water swirling in a whirling fishbowl. The fluid can then supply energy to the crust at that point. This is most likely the cause of both of the faults that bookended the quick radio burst, according to the paper’s authors.

Should the original error have resulted in a surface crack on the magnetar, it may have triggered a volcanic eruption-like outpouring of material from the star’s innards into space. The magnetar decelerates rapidly, and the researchers believe this could be the reason for it. Spinning objects slow down when they lose mass.

Consequences for Upcoming Studies

However, the scientists can’t be certain which of these elements—or others, such the magnetar’s strong magnetic field—might cause the creation of a rapid radio burst because they have only seen one of these events in real time. Some may have nothing to do with the outburst.

“We’ve unquestionably observed something important for our understanding of fast radio bursts,” said George Younes, a researcher at Goddard and a member of the NICER science team specializing in magnetars. “But I think we still need a lot more data to complete the mystery.”

The paper “Rapid spin changes around a magnetar fast radio burst” was published in Nature on February 14, 2024, and was authored by Chin-Ping Hu, Takuto Narita, Teruaki Enoto, George Younes, Zorawar Wadiasingh, Matthew G. Baring, Wynn C. G. Ho, Sebastien Guillot, Paul S. Ray, Tolga Güver, Kaustubh Rajwade, Alice K. Harding, and Keith C. Gendreau.

Additional Information About the Mission

NuSTAR is a NASA Science project Directorate in Washington, D.C.-based Small Explorer project headed by Caltech and overseen by NASA’s Jet Propulsion Laboratory in Southern California. NuSTAR was developed in collaboration with the Italian Space Agency (ASI) and Danish Technical University. Orbital Sciences Corp. of Dulles, Virginia, manufactured the spacecraft. The official data archive for NuSTAR is located at NASA’s High Energy Astrophysics Science Archive Research Center at NASA’s Goddard Space Flight Center, while the mission operations center is housed at the University of California, Berkeley. The mission’s ground station and mirrored data archive are provided by ASI. NASA has Caltech in charge of JPL.

Topics #Enigmatic Deep Space Signals #NASA Telescopes