Closing In on Fast Radio Bursts
Astronomers claim to have identified the source of one instance of the most enigmatic explosions in the universe.
Three years ago, CEH reported on rising interest in mysterious rapid bursts in space (28 Feb 2017). Some of these only lasted a few milliseconds. Named “fast radio bursts” (FRBs), these phenomena were so new to astronomy (due to improved detectors), physicists did not understand what caused them. They didn’t even know if they were at cosmological distances. If so, they had to be extremely powerful. Many of them emit X-rays and radio waves; a few seem to repeat. Now, astronomers claim they have identified the source of one from within the Milky Way galaxy. They believe the source is a magnetar – a very compact neutron star with an enormous magnetic field.
The magnetic fields of magnetars are a hundred to a thousand times as strong as those of other neutron stars – strong enough to distort the electron clouds of atoms, says grad student Chris Bochonek of Caltech in a podcast on Nature. Surprisingly, this extremely energetic explosion came from an object he believes is the size of Manhattan, he comments.
Weird space radio signal tracked to its source for the first time (New Scientist). Leah Crane gives an overview of FRBs, focusing on the observation tied to a location in the Milky Way. One “wow” factoid is that the energy of this burst in one millisecond is equal to three times the energy emitted every second by our sun. And this one may not be anywhere near the power of more distant FRBs. Astronomers are not sure if magnetars are the only way these bursts can be generated.
The proximity of this burst made it appear extremely bright. “It is much brighter than any other radio object in space, by a large margin,” says Bing Zhang at the University of Nevada, Las Vegas, one of the researchers who helped connect the FRB to its magnetar source.
Astronomers Discover Clues that Unveil the Mystery of Fast Radio Bursts (University of Nevada, Las Vegas). Bing Zhang, the author a theoretical paper on FRBs (see below) and a UNLV astrophysicist, is featured in this overview of the subject and the recent detection.
FAST helps reveal the origin of fast radio bursts (Phys.org). This article from the Chinese Academy of Sciences describes observations of FRBs by the Five-hundred-meter Aperture Spherical radio Telescope (FAST), and attempts to correlate FRBs with another type of object called soft gamma-ray repeaters (SGRs). The Milky Way burst seems to associate the two.
Mysterious ‘fast radio burst’ traced to a known object in the Milky Way for the first time ever (Live Science). This article quotes one of the co-authors of the studies, Daniel Michilli.
“This is the most powerful radio burst ever detected in our galaxy, which is exciting on its own,” Michilli, an astrophysicist with the FRB-hunting Canadian Hydrogen Intensity Mapping Experiment (CHIME), said in an email. “But now we finally have evidence of at least one object that can produce FRBs. Magnetars were already one of the main candidates, so it is a nice confirmation of our theories.”
A fast radio burst in our own Galaxy (Nature News & Views). This overview article gives some background on FRBs and theories about them. Then it describes how multiple observatories were able to trace the burst to its location in the sky.
The name ‘fast radio bursts’ is a good description of what they are: bright bursts of radio waves with durations roughly at the millisecond scale. First discovered7 in 2007, their short-lived nature makes it particularly challenging to detect them and to determine their position on the sky. The smorgasbord of theories that has been proposed to explain FRBs has, until recently, outpaced our discovery of actual FRB events. The majority of these theories invoke some kinds of stellar remnant as FRB sources. In particular, highly magnetized young neutron stars known as magnetars have emerged as leading candidates, because their strong magnetic fields could act as ‘engines’ that drive FRBs.
A fast radio burst associated with a Galactic magnetar (Nature). This paper by Bochonek et al. is the first of several papers in the special issue of Nature about the object observed on 28 April 2020. They say the burst, only lasting about a millisecond, was 4,000 times greater than the rotating radio source in the Crab Nebular pulsar.
A bright millisecond-duration radio burst from a Galactic magnetar (Nature). The CHIME/FRB Consortium issued this detailed report about the physics of FRBs as learned from observations of this “extremely intense radio burst from the Galactic magnetar SGR 1935+2154.” They believe a magnetar like this could only burst once every 500 years or so.
The fluence of this two-component bright radio burst and the estimated distance to SGR 1935+2154 together imply a burst energy at 400 to 800 megahertz of approximately 3 × 1034 erg, which is three orders of magnitude higher than the burst energy of any radio-emitting magnetar detected thus far.
No pulsed radio emission during a bursting phase of a Galactic magnetar (Nature). This paper by Lin et al. uses radio emissions measured after the burst to constrain the physical characteristics of FRB sources.
The physical mechanisms of fast radio bursts (Nature). This submission by Bing Zhang explores possible physical mechanisms of FRBs based on accumulated observations within this “fast-growing field.”
Here is good observational science at work. Observe. Measure. Using known physical laws, constrain the possible models. Don’t overstate the favored model. Stay open to alternative theories. Spare readers the speculation about origins and evolution. In these papers, “evolution” and big bang were not mentioned. Good work.
The story also shows how many bizarre phenomena exist in space that have only recently been discovered and are poorly understood. It’s not the static, placid universe of 19th century astronomers any more. Solomon, a royal “scientist” of his day, said it was the glory of kings to search out a matter (Proverbs 25:2). As photons from distant worlds fill our eyes and instruments, the wonders of God’s universe will undoubtedly keep scientists busy for many years to come (Psalm 19:1-4).