Astronomers have received a strange signal from space. What makes the signal strange? What might have caused that signal? What is all the buzz about? And can the signal be coming from aliens?
Let me answer the last question first. No, scientists do not think the signals come from aliens. For one, the source of the signal is 1.5 billion light-years away. That means the signal detected by the scientists left its source 1.5 billion years ago. Saying hello and expecting a reply 3 billion years later is not a likely thing for intelligent aliens to do.
More importantly, however, astronomers dealing with strange signals from space always work under the assumption that “it’s never aliens”—until of course, it is. What this means is that astronomers are humble enough to know that there is so much that they do not understand about the universe. Our universe is populated by strange things, and the history of astrophysics is filled with the detection of strange, at first inexplicable signals that later turn out to be produced by crazy objects that expand our understanding of the universe.
So what is all the fuss about?
One day it might be aliens. In the meantime, astrophysicists work hard to understand the limits of what natural objects can do. The more they understand the kinds of signals that can be generated by exploding stars, colliding black holes, or some other yet undiscovered phenomenon, the better they will be at distinguishing natural signals from signals that cannot be explained by astrophysics alone.
To understand fully understand what this means, it helps to review the facts.
The signal in question is an example of a fast radio burst or FRB. It was detected by astrophysicists working with the Canadian Hydrogen Intensity Mapping Experiment or CHIME in British Columbia, Canada. The team announced their discovery on 9 January of this year.
As the name suggests, FRBs are very fast, very bright bursts of radio waves.
Radio waves are a kind of electromagnetic radiation. Radio waves are similar to visible light, except we cannot see them because our eyes are not sensitive to them. We can, however, detect them with instruments. We even use them in technologies such as radio and television broadcasting.
Astronomers have so far detected around 60 FRBs. Of that number, 13 were detected by the CHIME observatory, which began operation last year. Astronomers do not know yet what causes these strange signals. They are, for now, a cosmic mystery.
One thing about FRBs that puzzles astronomers is how bright they are. During its brief flash, lasting only a fraction of a millisecond up to a few milliseconds, an FRB can produce more energy than our Sun does in a day. Whatever produces these FRBs are very violent events, and we are lucky we are not near a source of an FRB. Anything within a few light years of an FRB source would probably be fried during the event that causes them.
The recently detected signal is an even stranger thing than most other FRBs. Most sources of FRBs only produced one burst of radio signal. The signal detected by the team at CHIME came from the second source that produced repeating FRBs.
Almost every other FRB so far detected consisted of one burst of radio signal. The signal detected by the team at CHIME represents only the second time astronomers observed a repeating FRB. The first repeating FRB was discovered by astronomer Paul Scholz at McGill University in Canada. He noticed that several FRBs seemed to come from the same location as a previously discovered source 3 billion light years away.
With the second discovery of a repeating source of FRB, scientists have confirmed that whatever produced these strange flashes in the sky were capable of doing it repeatedly, at least some of the time. This helps in narrowing down the list of possible suspects.
For now, the top candidates are merging very dense objects, such as neutron stars or black holes. Neutron stars are very dense stars that can be as small as a city but have masses up to 29 times greater than the Sun’s. Black holes, on the other hand, are so dense and massive that not even light can escape their strong gravitational pull.
Other suspects are very bright supernovae, which are the explosions produced by dying stars, and so-called blitzars, small spinning stars that collapse into black holes.
Although probably not produced by intelligent extraterrestrials, solving the mystery of FRBs is still an important step in cataloging the kinds of signals we expect from natural sources. Because one day, we may finally detect one that cannot be explained by the usual suspects.