Near the beginning of 2020, scientists with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) released a paper which announced an interesting discovery. Not only was the earth receiving far more FRB’s than previously thought, they had observed that FRB 180916.J0158+65 was repeating every 16.35 days. FRBs or fast radio bursts are sudden large pulses of radiation that erupt from somewhere outside our galaxy. Though they last for fractions of a second, they expend an immense amount of energy, maybe as much as hundreds of millions of Suns.
Imagine that you are standing on your roof and in a city 1,000 miles (1,609 km) away from you, your friend is also standing on their roof. Your friend quickly shouts ‘Hi!’ to signal you. Think about how loud they would have to shout for you to hear–not only are you far away, but there are obstacles like buildings that may block or bounce sound. Also, there’s traffic and a lot of other noise pollution between you two. Now scale this communication scenario up a bazillion times and you have a sense of just how much radiation an FRB has to emit for our radio telescopes on earth to detect it. Space is a surprisingly noisy place, not sound wise, but in terms of celestial bodies giving off energy.
NASA has actually recorded a number of emissions such as radio waves from the sun’s corona or Jupiter’s magnetic fields. Since we first discovered FRBs in 2007, we’ve made it a point to specifically listen for them. So far, we’ve detected 150 emissions, out of those, only 11 have repeated. The rest have been one offs that have come from different directions and from various galaxies. Research shows that for some of the repeating FRBs, with each cluster of repetition the signal experiences frequency drift and get weaker. After a few repeats the signals seem to vanish.
Actually, that doesn’t mean the signal stopped, it just that many have become faint or lost among all the other noise the telescope has picked up. This suggests that some of what we consider to be one off FRBs probably repeat too, we just don’t detect the repetition. One researcher has described FRBS as massive at their source, but the strength of the signal reaching Earth is 1,000 times weaker than a signal from a mobile phone broadcasting from the Moon. In fact, some researchers suggest that earth is receiving thousands of FRBs a day–we simply don’t notice because we’re only looking at small regions of the sky for short periods of time and our telescopes aren’t (yet!) sensitive enough to detect everything.
Excitingly, the signals for FRB 180916.J0158+65 have remained fairly consistent. After a year of observation, researchers were able to confirm that FRB 180916.J0158+65 has a distinct pattern where over the course of four days, the signal would release a burst or two each hour. Then, it would go silent for another 12 days and repeat. 28 separate clusters of signal bursts were recorded from September 16, 2018 through October 30, 2019 for a total of 409 days. Interestingly, each burst of signals has been different. As of yet, there’s been no discernable repeating or overlap of the signal. However, there are enough similarities between the flares to suggest that they are part of a single repeating pattern.
Currently, researchers only have been able to pinpoint the location of where eight FRBs originated from, including 180916.J0158+65. This FRB is coming from the edges of nearby spiral galaxy SDSS J015800.28+654253.0, another catchy name which according to scientists is similar to our Milky Way. Unfortunately, by the term nearby we mean 457 million light-years away from our solar system. However, by far it’s the closest FRB we’ve discovered; the first repeating FRB traced, FRB 121102, originates in a small dwarf galaxy with a high rate of star formation some three billion light-years from Earth.
To answer the question probably buzzing through your brain right now–Are FRBS, and this FRB in particular, aliens attempting to contact us? The simple answer is possibly FRBS are quite mysterious. Currently scientists can only speculate about what causes them, so we can’t entirely discount the fact that aliens are signaling us directly or pinging the universe, possibly hoping to find signs of intelligent life.
However, it’s kind of unlikely that the radiation emissions would be produced by aliens. If you’re a highly intelligent life form who eons ago. Remember the energy from FRB 180916.J0158+65 is taking some 457 million years to reach us, had the capacity to build one or more huge, probably solar powered transmitting devices that can hurtle immense amounts of radio waves into space to hopefully signal your neighbors and alert then to the fact that you exist. Wouldn’t you send the same message several times so that you could make contact and be clearly understood?
Sending different signal bursts or messages each time would be kind of like at the same time each day dialing a random phone number for another country out of a directory and letting it ring once before hanging up and doing that over and over again to try to communicate with other people. Of course, on the other hand there is a chance that the aliens are intellectually superior to us and they are sending a distinct message with FRB 180916.J0158+65, but we humans are too dumb to figure it out.
Even if the FRB was sent by aliens, unfortunately their civilization is already lost to time since the bursts have taken close to 500 million light years to reach earth. More likely than aliens, FRBs are caused by a particular celestial event. Since FRBs last only milliseconds, researchers think their sources might be small, celestial objects only a few hundred kilometers across. Currently, one theory about the creation of FRBs that researchers are exploring is that FRBs are flares from dying stars known as “blitzars”.
As a blitzar exhausts its nuclear fuel and collapses when it can no longer support its weight, it spews radiation. Another theory is that FRBs are caused by the interaction between neutron stars and early OB-type star binary systems. Neutron stars are the remnants of supernovae. Diameter wise, they aren’t particularly large, may be the size of a large city such as Chicago, but they are extremely dense, with masses much heavier than our sun. OB-type stars are short-lived, hot, massive, bright burning stars. The interaction between these two heavenly bodies, and the wind coming off of the OB-type star, could create radiation spikes.
Yet, another theory is that FRBs are created by magnetars–rare neutron stars with incredibly powerful magnetic fields. Astronomers have observed magnetars suddenly flaring in an immense burst. Possibly these bursts are caused by starquakes, a sudden disturbance of the magnetars’ structures that releases built-up stresses from their swirling magnetic fields. Some of the energy is most likely expressed as radio waves. While a sudden random, cataclysmic event such as star collapse or starquake makes sense in terms of causing a non-repeating FRB, it doesn’t quite make sense for repeating FRBS such as 180916.J0158+65.
The implication being that if this FRB repeats on a regular basis, something has to be controlling the cycle. One of the theories postulated by the scientists who authored the paper is that the FRB is being modulated by an orbital motion. The area the FRB originated from is a star-forming region just outside the main galaxy, perhaps the FRB is caused by interaction between a star and a stellar-mass black hole. Or the waves could be giant radio pulses from a very active neutron star that is being eclipsed by a companion object. When the celestial object isn’t being obscured, it transmits toward earth. It’s far less likely, but possible that the source for this repeating FRB is a single celestial object such as a magnetar or X-ray pulsar. Researchers find the data they’ve parsed doesn’t really support this theory.
Both magnetars and pulsars have a wobbling rotation that produces periodicity; however, none are known to wobble that slowly. Also, there’s a slight chance that aliens could be using their device to transmit at the same time in some sort of cycle only known to them. For FRB 180916.J0158+65 scientists have along term chance to study the signal clusters to figure out exactly what causes the energy bursts. This may provide insight for figuring out patterns, behaviors and root causes of other FRBs and ultimately help researchers gain a clearer understanding of our universe.