‘Alien’ Radio Burst: Scientists identify source of Milky Way’s first known radio burst

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November 5, 2020 9:50 PM

Researchers have published a series of studies in Nature journal to explain what is causing these radio bursts.

The source of these bursts was already being observed for half a by the astronomers when the flare-up occurred. (Image: NASA's Goddard Space Flight Center/Chris Smith (USRA))

Radio burst: Back in April-end, a fast radio burst (FRB) had been detected from within the Milky Way galaxy for the first time ever. Now, scientists have identified what caused these blasts, and this marks the first identification of such FRBs, which had been discovered back in 2007 when they had originated in far away galaxies. Researchers have published a series of studies in Nature journal to explain what is causing these radio bursts, and in this, NASA missions have also helped them. So what exactly is causing these FRBs? The answer — remains of a super-magnetised star known as magnetar.

NASA’s Jet Propulsion Laboratory (JPL) has stated that this magnetar had blasted out X-ray and radio signals simultaneously in April and something like that had never been observed before. The flare up demonstrated that magnetars could produce powerful radio blasts which had only been observed in other galaxies before.

Milky Way radio burst: What are magnetars?

According to Caltech University, where the lead author of one of the studies is pursuing a doctoral in astrophysics, magnetars are the spinning remains of stars, and they are left over from explosions that occurred in massive stars. NASA says that these are a type of isolated neutron stars, and they are city-sized remains of stars much more massive than our Sun. What distinguishes these magnetars from dead stars is the extreme magnetic fields they have. To put this field in context, NASA says that this magnetic field can be about 10 trillion times stronger than that of a refrigerator magnet, and can be up to a thousand times stronger than the field of a typical neutron star.

Speculations regarding FRBs

Caltech University astrophysics doctoral student Chris Bochenek said that there have been a wide variety of speculations regarding the origin of such radio blasts, especially when the only ones researchers had caught were originating from other galaxies.

Some theories have gone even as far as speculating alien intervention as the cause of these radio bursts.

However, Bochenek is of the view that while there may be several twists and turns regarding FRBs in the future, at this point, according to him, the FRBs are mostly caused by magnaters, and to him it would remain so until proven otherwise.

Milky Way radio burst: Process of capturing the blast

According to NASA JPL, several satellites, including the space agency’s Wind mission, had captured the X-ray portion of the blasts.

Meanwhile, the radio signals of the bursts had been detected by the Canadian Hydrogen Intensity Mapping Experiment (CHIME). CHIME is a radio telescope situated in British Columbia-based Dominion Radio Astrophysical Observatory. It is managed by the Montreal-based McGill University, University of Toronto, and the University of British Columbia.

At the same time, NASA-funded Survey for Transient Astronomical Radio Emission 2 or STARE2 also detected these bursts. STARE2 is a project that consists of a trio of detectors based in Utah and California. It is operated jointly by Caltech as well as NASA JPL. From Caltech, Bochenek and Shri Kulkarni lead the project, while from JPL, the project is led by Konstantin Belov. It was this team that was able to determine that the energy from the burst had been comparable to FRBs.

The source of these bursts was already being observed for half a by the astronomers when the flare-up occurred.

A day before the FRB, NASA’s Neil Gehrels Swift Observatory detected a round of activity occurring in the SGR 1935+2154 or SGR 1935 magnetar. The activity marked this magnetar’s most prolific flare-up by then as it spewed a storm of X-ray bursts in rapid-fire mode, with each burst lasting for less than a second. This storm raged for hours. During this time, the activity was picked up multiple times by Swift, along with the Fermi Gamma-ray Space Telescope of NASA and the Neutron star Interior Composition Explorer (NICER) X-ray telescope of NASA which is mounted on the International Space Station.

Once the storm had ended and Swift, NICER and Fermi could no longer view the magnetar, it gave out a special burst, which was now observed by different missions maintained by European, Chinese and Russian space agencies. It was during this half-second X-ray flare up that CHIMEand STARE2 detected the thousandth-of-a-second-long radio burst.

Paul Scholz, a member of the CHIME/FRB collaboration, said that the radio burst was brighter by a wide margin than anything else they had observed and therefore, it was highly exciting. Chris, meanwhile, said that when he saw the data, he “basically felt paralysed” because they had been able to catch the FRB head-on.

NASA said that while the distance of SGR 1935 is not known, it is estimated to be between 14,000 to 41,000 light years away from the Earth. If the magnetar is on the nearer end, then it would translate to the stellar remnant having produced enough energy in the X-ray portion of that historic burst as is produced by the Sun in a month. What is more interesting is the fact that it was not even the most powerful flare it had thrown out, as the storm eruption had resulted in more powerful bursts.

What does this mean?

The observations due to this event suggests that the magnetar had produced a flare that marked the Milky Way equivalent of an FRB. This translates to the possibility that at least some of these signals are also produced by magnetars in other galaxies.

However, to be sure of this magnetar connection, the scientists would ideally want to find an FRB from a nearby galaxy which would coincide with an X-ray burst from the same source.

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