Jan 11 2018

Fast Radio Bursts – Still Not Aliens

This is a (sort of) follow up to my previous post. Fast Radio Bursts (FRBs) are a legitimate astronomical mystery, and very interesting. They are very brief (30 microseconds to 9 milliseconds) and very powerful bursts of radio waves. To date about 30 FRBs have been detected. Most of these FRBs are one-offs – they occur once and never repeat (at least so far). There is one exception, however, FRB 121102 (more on that below).

What do we know about FRBs so far? They are isotropic, which means they occur all over the sky. They are not concentrated in the galactic disk. This by itself implies they are extragalactic. But also analysis of the radio bursts indicate that they have traveled through intergalactic plasma, for billions of light years. So they must also be incredibly powerful. The radio waves are broadband, so they are spread throughout the radio wavelengths. They are also highly polarized, which means they were aligned at their creation with a strong magnetic field.

Because they are radio bursts, they are studied by radio astronomers, which includes SETI astronomers, whose primary mission is to survey the sky for possible alien communications. In an SGU interview with SETI astronomer Seth Shostak he indicated that SETI does a lot of non-ET-related astronomy. This is a good example of that – they are helping to detect and analyze FRBs, including analysis of FRB 121102.

FRB 121102 is the only known FRB repeater, and so far we have detected a few hundred bursts from this same location. This has afforded astronomers the unique opportunity to more closely examine this FRB. A recent additional 15 bursts from 121102 have allowed astronomers to pinpoint the location to a star-forming region in a dwarf galaxy more than 3 billion light-years from Earth. Analysis of these bursts also shows that they are 100% linearly polarized, again indicating they are produced within a powerful magnetic field.

What this likely means is that the source of these FRBs is a massive black hole. Rotating plasma falling into massive black hole can generate a powerful magnetic field. This black hole is interacting with something to generate the FRBs.

Perhaps all FRBs come from massive black holes, but most result from rare and isolated events, while 121102 has a neighbor or something which allows for their repeated creation.

But keeping with the theme that all astronomical mysteries may be aliens until proven otherwise, SETI is analyzing the FRB 121102 signals to see if they contain any modulated information – complex information that would not be expected to come from a natural source.

It is reasonable to conduct this kind of analysis. We don’t know what we don’t know, and who can say what a superadvanced alien technological civilization could be capable of. At the very least this project will hopefully give them more experience in analyzing radio signals for interesting patterns, and may discover something non-alien but interesting about FRBs. It’s all good.

But I am not holding my breath that FRBs will turn out to be alien in origin. They clearly have a natural source. Hiding a signal in them would mean manipulating an interaction with a massive black hole in order to encode a signal in the FRB somehow. If you could pull something like this off, it would create a beacon you can send across the universe. But messing with supermassive black holes just seems unlikely. I’m happy to be surprised, but again, just not expecting to be.

The alien angle aside – FRBs are clearly the result of some interesting and powerful astronomical event. They may not be rare (well, not rare when you have the entire visible universe to survey). One estimate is that there may be thousands of FRBs visible somewhere in the universe every day. If that’s true we should start finding many more examples to study.

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