Fast Radio Bursts (FRBs) are among the most mysterious astronomical phenomena facing astronomers today. While hundreds of bursts have been detected since the first-ever recorded detection of an FRB in 2007 – the Lorimer Burst – astronomers are still unsure what causes them. Even more mysterious, some have occasionally been found to be repeating in nature, which has fueled speculation that they may not be natural in origin (i.e., possible alien transmissions?). Astronomers are naturally very excited whenever a repeating FRB is found, as it gives them the chance to examine them closer.
In a recent survey, an international team of scientists used three major telescopes worldwide to study a repeating FRB (known as FRB 190520) that was first observed in 2019. According to their observations, this particular FRB is not just a repeating source from a compact object but a persistent one that emits low-level bursts of radio waves between larger ones. These findings raise new questions about the nature of these mysterious objects and how they can be used as tools to probe the space between stars and galaxies.
Astronomy is progressing rapidly these days, thanks in part to how advances in one area can contribute to progress in another. For instance, improved optics, instruments, and data processing methods have allowed astronomers to push the boundaries of optical and infrared to gravitational wave (GW) astronomy. Radio astronomy is also advancing considerably thanks to arrays like the MeerKAT radio telescope in South Africa, which will join with observatories in Australia in the near future to create the Square Kilometer Array (SKA).
In particular, radio astronomers are using next-generation instruments to study phenomena like Fast Radio Bursts (FRBs) and neutron stars. Recently, an international team of scientists led by the University of Manchester discovered a strange radio-emitting neutron star with a powerful magnetic field (a “magnetar”) and an extremely slow rotational period of 76 seconds. This discovery could have significant implications for radio astronomy and hints at a possible connection between different types of neutron stars and FRBs.
In the near future, CHIME will be getting an expansion that will help it more accurately identify where FRBs are coming from. This will consist of a new radio telescope outrigger located at the SETI Institute’s Hat Creek Radio Observatory (HCRO), new outriggers near Princeton, British Columbia, and at the Green Bank Observatory in West Virginia. These will work with the main CHIME telescope to localize CHIME-detected FRBs precisely in the night sky.
Located in the Okanagan Valley outside of Penticton, British Columbia, there is a massive radio observatory dedicated to observing cosmic radio phenomena. It’s called the Canadian Hydrogen Intensity Mapping Experiment (CHIME), a cylindrical parabolic radio telescope that looks like what snowboarders would call a “half-pipe.” This array is part of the Dominion Radio Astrophysical Observatory (DRAO), overseen by the National Research Council (NRC).
Originally, the observatory was meant to detect radio waves from neutral hydrogen gas in the early Universe. Today, it is used for other objectives, such as detecting and studying Fast Radio Bursts (FRBs). Since it became operational, CHIME scientists have been busy sorting through terabytes of data to pinpoint signals, often finding several in a single day. To assist with all this data-mining and coordinate CHIMEs efforts with other facilities worldwide, scientists from McGill University have developed a new system for sharing the enormous amount of data CHIME generates.
The energetic phenomena known as Fast Radio Bursts (FRBs) are one of the greatest cosmic mysteries today. These mysterious flashes of light are visible in the radio wave part of the spectrum and usually last only a few milliseconds before fading away forever. Since the first FRB was observed in 2007, astronomers have looked forward to the day when instruments of sufficient sensitivity would be able to detect them regularly.
Much like Dark Matter and Dark Energy, Fast Radio Burst (FRBs) are one of those crazy cosmic phenomena that continue to mystify astronomers. These incredibly bright flashes register only in the radio band of the electromagnetic spectrum, occur suddenly, and last only a few milliseconds before vanishing without a trace. As a result, observing them with a radio telescope is rather challenging and requires extremely precise timing.
Hence why the Dominion Radio Astrophysical Observatory (DRAO) in British Columbia launched the Canadian Hydrogen Intensity Mapping Experiment (CHIME) in 2017. Along with their partners at the National Radio Astronomy Observatory (NRAO), the Massachusetts Institute of Technology (MIT), the Perimeter Institute, and multiple universities, CHIME detected more than 500 FRBs in its first year of operation (and more than 1000 since it commenced operations)!
In September of 2017, the Canadian Hydrogen Intensity Mapping Experiment (CHIME) in British Columbia commenced operations, looking for signs of Fast Radio Bursts (FRBs) in our Universe. These rare, brief, and energetic flashes from beyond our galaxy have been a mystery ever since the first was observed a little over a decade ago. Of particular interest are the ones that have been found to repeat, which are even rarer.
Before CHIME began collecting light from the cosmos, astronomers knew of only thirty FRBs. But thanks to CHIME’s sophisticated array of antennas and parabolic mirrors (which are especially sensitive to FRBs) that number has grown to close to 700 (which includes 20 repeaters). According to a new study led by CHIME researchers, this robust number of detections allows for new insights into what causes them.
Fast Radio Bursts (FRBs) have become a major focus of research in the past decade. In radio astronomy, this phenomenon refers to transient radio pulses coming from distant cosmological sources, which typically last only a few milliseconds on average. Since the first event was detected in 2007 (the “Lorimer Burst”), thirty four FRBs have been observed, but scientists are still not sure what causes them.
With theories ranging from exploding stars and black holes to pulsars and magnetars – and even messages coming from extra-terrestrial intelligences (ETIs) – astronomers have been determined to learn more about these strange signals. And thanks to a new study by a team of Australian researchers, who used the Australia Square Kilometer Array Pathfinder (ASKAP), the number of known sources of FRBs has almost doubled.
Astronomy can be a tricky business, owing to the sheer distances involved. Luckily, astronomers have developed a number of tools and strategies over the years that help them to study distant objects in greater detail. In addition to ground-based and space-based telescopes, there’s also the technique known as gravitational lensing, where the gravity of an intervening object is used to magnify light coming from a more distant object.
Recently, a team of Canadian astronomers used this technique to observe an eclipsing binary millisecond pulsar located about 6500 light years away. According to a study produced by the team, they observed two intense regions of radiation around one star (a brown dwarf) to conduct observations of the other star (a pulsar) – which happened to be the highest resolution observations in astronomical history.
The study, titled “Pulsar emission amplified and resolved by plasma lensing in an eclipsing binary“, recently appeared in the journal Nature. The study was led by Robert Main, a PhD astronomy student at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics, and included members from the Canadian Institute for Theoretical Astrophysics, the Perimeter Institute for Theoretical Physics, and the Canadian Institute for Advanced Research.
The system they observed is known as the “Black Widow Pulsar”, a binary system that consists of a brown dwarf and a millisecond pulsar orbiting closely to each other. Because of their close proximity to one another, scientists have determined that the pulsar is actively siphoning material from its brown dwarf companion and will eventually consume it. Discovered in 1988, the name “Black Widow” has since come to be applied to other similar binaries.
The observations made by the Canadian team were made possible thanks to the rare geometry and characteristics of the binary – specifically, the “wake” or comet-like tail of gas that extends from the brown dwarf to the pulsar. As Robert Main, the lead author of the paper, explained in a Dunlap Institute press release:
“The gas is acting like a magnifying glass right in front of the pulsar. We are essentially looking at the pulsar through a naturally occurring magnifier which periodically allows us to see the two regions separately.”
Like all pulsars, the “Black Widow” is a rapidly rotating neutron star that spins at a rate of over 600 times a second. As it spins, it emits beams of radiation from its two polar hotspots, which have a strobing effect when observed from a distance. The brown dwarf, meanwhile, is about one third the diameter of the Sun, is located roughly two million km from the pulsar and orbits it once every 9 hours.
Because they are so close together, the brown dwarf is tidally-locked to the pulsar and is blasted by strong radiation. This intense radiation heats one side of the relatively cool brown dwarf to temperatures of about 6000 °C (10,832 °F), the same temperature as our Sun. Because of the radiation and gases passing between them, the emissions coming from the pulsar interfere with each other, which makes them difficult to study.
However, astronomers have long understood that these same regions could be used as “interstellar lenses” that could localize pulsar emission regions, thus allowing for their study. In the past, astronomers have only been able to resolve emission components marginally. But thanks to the efforts of Main and his colleagues, they were able observing two intense radiation flares located 20 kilometers apart.
In addition to being an unprecedentedly high-resolution observation, the results of this study could provide insight into the nature of the mysterious phenomena known as Fast Radio Bursts (FRBs). As Main explained:
“Many observed properties of FRBs could be explained if they are being amplified by plasma lenses. The properties of the amplified pulses we detected in our study show a remarkable similarity to the bursts from the repeating FRB, suggesting that the repeating FRB may be lensed by plasma in its host galaxy.”
It is an exciting time for astronomers, where improved instruments and methods are not only allowing for more accurate observations, but also providing data that could resolve long-standing mysteries. It seems that every few days, fascinating new discoveries are being made!
Fast Radio Bursts (FRBs) have fascinated astronomers ever since the first one was detected in 2007. This event was named the “Lorimer Burst” after it discoverer, Duncan Lorimer from West Virginia University. In radio astronomy, this phenomenon refers to transient radio pulses coming from distant cosmological sources, which typically last a few milliseconds on average.
Over two dozen events have been discovered since 2007 and scientists are still not sure what causes them – though theories range from exploding stars and black holes to pulsars and magnetars. However, according to a new study by a team of Chinese astronomers, FRBs may be linked to crusts forming around “strange stars”. According to a model they created, it is the collapse of these crusts that lead to high-energy bursts that can be seen light-years away.
As they state in their study, all previous attempts to explain FRBs have been unable to resolve where these strange phenomena come from. What’s more, no counterparts in other wavebands have been detected for non-repeating FRBs so far and research into their origins has been confounded by the study of repeating FRBs. This is due to the fact that the former are often attributed to catastrophic events, which are incapable of repeating.
In the case of the FRBs, these catastrophic events include “magnetar giant flares, the collapses of magnetized supramassive rotating neutron stars, binary neutron star mergers, binary white dwarf mergers, collisions between neutron stars and asteroids/comets, collisions between neutron stars and white dwarfs, and evaporation of primordial black holes.”
Alternately, in the case of the repeating FRBs, various models suggest that these could be caused by “highly magnetized pulsars traveling through asteroid belts, neutron star-white dwarf binary mass transfer, and star quakes of pulsars.” For the sake of their study, the team proposed a new model whereby the build up and collapse of matter on certain types of neutron stars (aka. “strange stars”) could explain the behavior of FRBs. As they explain:
“It has been conjectured that strange quark matter (SQM), a kind of dense material composed of approximately equal numbers of up, down, and strange quarks, may have a lower energy per baryon than ordinary nuclear matter (such as 56 Fe) so that it may be the true ground state of hadronic matter. If this hypothesis is correct, then neutron stars (NSs) may actually be ‘strange stars'”.
According to this model, strange stars build up a layer of hadronic (aka. “normal”) matter on their surface over time. As these SQM stars accrete matter from their environment, their crusts becomes heavier and heavier. Eventually, this leads the crust to collapse, leaving a hot and bare strange star that becomes a powerful source of electrons and positron pairs.
These pairs would then be released along with large amounts of magnetic energy over a very short timescale. The team further hypothesized that during a collapse, a fraction of magnetic energy would be transferred to the polar cap region of the SQM stars, where the magnetic field energy is released. This would cause the electrons and positrons to be accelerated to ultra-relativistic speeds, which would then expand along magnetic field lines to form a shell.
Beyond a certain distance from the star, coherent emission in radio bands will be produced, giving birth to an FRB event. They also theorize that this same phenomenon could give to rise to repeating FRBs. One possibility is that the crust of an SQM star could be reconstructed over time, thus allowing for repeated events. A second is that only small sections of crust collapse at any given time, thus resulting in repeated events.
As they conclude, further studies will be needed before this can be said either way:
Owing to this long reconstruction timescale, multiple FRB events from the same source seem not likely to happen in our scenario. Our model thus is more suitable for explaining the non- repeating FRBs… However, we should also note that during the collapse process, if only a small portion (in the polar cap region) of the crust falls onto the SQM core while the other portion of the crust remains stable, then the rebuilt timescale for the crust can be markedly reduced and repeating FRBs would still be possible.
Another thing that they claim will require further investigation is whether or not the collapse of a strange star’s crust could result in electromagnetic radiation other than radio waves. At present, any emissions in the X-ray and Gamma-ray bands would be too faint for current detectors to observe. For these reasons, further investigations of FRB sources with more sensitive instruments are needed.
These include the Canadian Hydrogen Intensity Mapping Experiment (CHIME) telescope – located in Penticton, British Columbia – and the Square Kilometer Array (SQA) currently under construction in South Africa and Australia. These facilities, which are optimized for radio astronomy, are expected to reveal a great deal more about FRBs and other mysterious cosmic phenomena.