- 22 Nov 2020
While the concept of radio bursts isn't new to scientists, this is the first time Earth has remained a witness to such extra mundane radiation. Fast radio bursts are bright bursts of radio waves from astronomical objects across galaxies. In a first, FRB 200428 was accompanied with X-rays and could be traced to a magnetar.
Image Credits: Harvard X-ray Observatory
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. A series of studies have been published in Nature Journal which further elucidates the exact cause behind these bursts and thus Magnetar becomes the cynosure of all eyes.
What exactly is a Magnetar?
Image Credits: SciTech daily
While no human is oblivious of the scariest thing in the universe-the one with an insatiable appetite and where the laws of physics are obliterated. Our own galaxy, Milky Way is home to a supermassive black hole Sagittarius A* which is constantly feeding on nearby stars and expanding itself. Magnetars may not be as frightening as those giant voids yet they are the most powerful objects, known to human.
Magnetars are remnants of exploded mammoth stars-stars which are at least eight times more massive than our Sun. When a star explodes in a beautiful supernova, its extremely dense and magnetic stellar core remains which later forms neutron stars. These neutron stars are composed of neutrons and spin very fast. Their high speed and immense magnetic field help them release electromagnetic radiation. These are called pulsars and can be observed if their poles face the Earth. Only a few of these pulsars are upgraded to the status of a Magnetar owing to their tremendous magnetic field. Magnetars are the strongest magnets in the universe. A unit called Gauss is used to realize the intensity of magnetic fields. Where Earth's magnetic field is calculated to be something around 0.6 Gauss, the magnetic field of a Magnetar can go up to one quadrillion Gauss. No wonder a Magnetar can turn all our atoms into dust in the blink of an eye!
How was the blast captured?
Image Credits: NASA
NASA stated that the blast comprised of both X-rays and radio signals-something that they have never observed before. These powerful radio blasts had been observed in other galaxies but it was the first such whopping radiations have managed to reach us.
According to NASA Jet Propulsion Laboratory (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.
Image Credits: NASA
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 led to the Magnetar's one of the most prolific flare where the cosmic monster spewed a storm of X-ray bursts, wich each burst lasting for a few milliseconds. This storm continued 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 CHIME and STARE-2 detected the thousandth-of-a-second-long radio burst.
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. The humongous energy of the Magnetar is evident from the fact that in 1/5th of a second, it released more energy than our Sun has released in the last 2,50,000 years. What's more astounding! This wasn't even the most dynamic flare that the Magnetar has thrown up, as the storm eruption had resulted in more powerful bursts.
What inference can be drawn from here?
In recent years, enigmatic events called fast radio bursts (FRBs) have captivated radio astronomers. However, due to lack of data, they were never certain of their origin. While some scientists believed them to be a source of communication generated by aliens trying to interact with us, a few believed that they were signs of strange cosmic events unknown to human. The problem was astronomers have only seen FRB-like events in distant galaxies, which always made them hard to study in detail. With the recent detection of these sporadic outbursts, astronomers are optimistic they’ve spotted a nearby example of a possible source of distant FRBs. What further promises their prognostication is the fact that the bright radio burst was spotted in the direction of a magnetar in our Milky Way called SGR 1935+2154, located in the constellation Vulpecula following unprecedented activities in the celestial body.
Before this, scientists had a very faint idea of the energy of Magnetars and their specific locations. While there are tons of Magnetars in and around our galaxy, whether they are a potential threat to humanity anytime soon is still under contemplation. With a Magnetar, so close to our galaxy, astronomers are anxious of driving starquakes which often destabilises Magnetars resulting in inevitable compression of Earth's magnetic field and thereafter wiping out of humanity. But such an event is extremely rare, like once in a million years. This data will further help researches to dive deeper into the dark mysteries of Universe.
How often do these fainter bursts happen? Are they beamed so not all radiation is equally bright in all directions? Do they fall on a spectrum of FRBs with varying intensities, or are they something entirely new? And how are the X-ray data connected?
And the neverending story of the inscrutable and mystifying universe continues. These are the questions that need to be understood and further analyzed before a definitive conclusion can be made. But until then, astronomers are excited to know this latest burst may finally lead to an answer to the years-long mystery about the origin of FRBs. And until they have that answer, they will keep scanning the skies for bursts both near and far.