This weekend, we were a bit confused and disturbed to see reporting on fast radio bursts that implied these bursts were the kind of radio signals SETI has been searching for.
Last week there was a series of press releases that came out during the American Astronomical Society meeting concerning one very specific fast radio burst – FRB 180916.J0158+65 – and its location in a not too distant spiral galaxy. At the time, we didn’t cover this story because there just wasn’t a lot to cover.
Fast Radio Bursts, or FRBs, are millisecond long bursts of radio emission that appear both as singular bursts and repeating bursts. The first FRB was discovered in archival data in 2007, and in the years since, attempts to discover the source of these bursts has been full of confusion. While archival searches have found bursts, observing them on purpose has been hard.
In 2010, 16 FRBs detected by Parkes Radio Telescope were found to be of terrestrial origin, and were associated with standard kitchen microwave ovens. While this led to some discussion that microwave ovens might be the source of all FRBs, the detection of a repeating FRB in 2012 quelled that line of thinking. That object, FRB 121102, has a highly variable pattern of bursts. It appears to be associated with – or at least aligned on the sky with – a dwarf galaxy about 3 billion light years from Earth. What the source is, well, the literature is a mess, but most guesses point toward some sort of a compact object, like a neutron star or black hole, having a strong magnetic field that is interacting with something somehow.
This kind of vague and inconclusive kind of observation is the norm for FRBs, and when a series of new releases came out last week, we looked at the science, and decided to pass over the releases in favor of other more definitive news. Last week a consortium of institutions announced that another repeating FRB has been identified with a location on the sky, and this time the alignment was with a star-forming region in a spiral galaxy. This region is sufficiently different from past observations to make the science about FRBs even more confusing. According to team member Kenzie Nimmo if the University of Amsterdam, “The found location is radically different from the previously located repeating FRB, but also different from all previously studied FRBs. The differences between repeating and non-repeating fast radio bursts are thus less clear and we think that these events may not be linked to a particular type of galaxy or environment. It may be that FRBs are produced in a large zoo of locations across the Universe and just require some specific conditions to be visible.”
In other words, we have little idea what FRBs are, and they could be a whole lot of different things… After all, we already know some are signals from other galaxies and some are Australian microwave ovens.
When there is a gap in understanding, it’s possible for people to guess at solutions, and in the case of FRBs, some have guessed that these signals are digitized shouts from alien civilizations – either pulsed communications we can’t understand, or just a burst of energy meant to say “Hey, we’re here.” While there is a non-zero chance one or some of the bursts can be explained this way, a non-zero possibility and a likely possibility aren’t the same, and what we’re seeing with the recurring bursts appears to be too energetic to rationally be created artificially, unless your way a forming things artificially includes the ability to alter the behaviors of stars and the materials falling onto compact objects.
So, to the headlines claiming astronomers have found the radio signals that SETI has been searching for … no. This is not definitive evidence of aliens, or actually definitive news of anything whatsoever. This is news that we have now, for the second time, figured out where on the sky a weird signal is coming from. That’s it. That’s all we know. A location, but not even a certain distance.
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