I have recently become aware of an astronomical phenomenon called fast radio bursts (FRBs). These are brief, almost laser-like flashes of intense radio-wave radiation that mostly appear to come from far-away galaxies. These phenomena were discovered in 2007, and they are difficult to study because they’re so brief and, usually, unpredictable. Nonetheless, since their discovery, sightly more than 100 have been identified. What causes them is still a mystery, though there are some clues.
I found three reports on FRBs in the popular science literature, some of it contradictory. First, there was a report on using the radiation from FRBs to study the density of matter in intergalactic space. The FRBs consist of a spectrum of radio frequencies. When traveling through empty space, these pulses are unaffected. However, when they encounter electrons, the lower frequency waves are slowed down more than the higher frequency waves. If the bursts that arrive on Earth are analyzed for the separation of frequencies, from highest to lowest (dispersion), and the location of the source is known, it’s possible to know how many electron the burst encountered on its journey. Thus, it’s possible to obtain a fairly good estimate on the matter density of empty space. This is an important question because only about half of the matter predicted to be in the universe by the Big Bang can actually be seen. (Note, we’re talking about ordinary matter here, the stuff that interacts with light, not dark matter.) It has been assumed that the rest of the matter is very thinly dispersed between the galaxies, but the study of the dispersion of the FRBs made it possible to determine if this was really true, and in fact, it appears to be so. The density of matter in intergalactic space, as determined by this study, agrees with the prediction from the Big Bang.
Second, there was a report describing the discovery of a FRB source within our own galaxy. The researchers were able to colocate the source of the FRB with a known neutron star with a very strong magnetic field, called a magnetar. Theorists have proposed that magnetars could be the source of FRBs under certain conditions, but given how far away most FRB sources are from Earth, there was no way of knowing. This newly discovered, much closer source appears to confirm the notion that magnetars can be the source of FRBs.
...Or not. The third report was on the discovery that some FRBs run on regular cycles. One that was the subject of a long-term study was found to have a cycle lasting a total of 157 days; during 90 of these days, bursts may be observed, while during the other 67 days, they aren’t. This may provide evidence that the source is orbiting around some massive object, such as a black hole or a neutron star:
Dr Kaustubh Rajwade of The University of Manchester, who led the new research, said: "This is an exciting result as it is only the second system where we believe we see this modulation in burst activity. Detecting a periodicity provides an important constraint on the origin of the bursts and the activity cycles could argue against a precessing neutron star."
The reason for doubting that a neutron star is the source of such an FRB is that it’s difficult to imagine a mechanism whereby such a source could be cyclical over a period 157 days in length.
Another name for a precessing neutron star is a magnetar. So while report #2 is evidence in favor of magnetars as FRB sources, report #3 provides evidence against this notion. Welcome to the world of new science! Nobody has any idea what’s going on so everybody is trying out new ideas and making new observations. Sometime the ideas fit the data, and sometimes they don’t. If they don’t the ideas need to be replaced or modified until they do. So nobody yet is sure what’s causing FRBs, but with more careful observations, maybe a consistent picture will emerge soon.
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Top Comment (June 11, 2020):
From mark schroeder:
This one is really good, I think.
From annieli's diary of June 11th, "domestic terrorists run by 'radical left Democrats' have taken over Seattle", STOOP THEM!
NorthBronxDem commented, "For a guy who doesn’t drink, he drunk tweets pretty good."
Highlighted by lineatus:
This comment from CharliePDX, who finds a compelling analogy for the condition of African Americans in the environment of institutionalized racism. From Mortifyd’s recommended post Mom Just Doesn’t Get It.
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