This year, radio telescopes in Canada have spotted something strange in a rare astronomical event known as a Fast Radio Burst (FRB). FRB’s were first detected in 2007; they are high intensity radio signals lasting only a few milliseconds that emanate from distant galaxies. And scientists know exactly what their cause is… Aliens… nah just kidding, they have no idea! Yet!
Since 2007 about 50 – 60 such events have been spotted, however, this is only the second time that a repeated signal (5 times) was detected emanating from exactly the same place, in the space of a few months. The first time this happened was in 2012 from a galaxy 2.5 billion light-years away (with a few repeat signals from that point). So this appears to not be some accident of measurement. Intriguing…
So where do these FRB’s come from? The 2012 ‘repeater’ came from a star-forming region in a dwarf galaxy (there are different types but it’s basically ‘a small galaxy’). Scientists think that this is no coincidence as it is likely that the conditions for these bursts would arise from some extreme astronomical environment.
Some have suggested that FRB’s arise in magnetars, a type of neutron star with a powerful magnetic field that are thought to arise as a result of unusually large supernova explosions; thought to be prevalent in dwarf galaxies. Others suggest that supermassive black holes in active galactic nuclei (AGN) are the cause. AGN’s are high luminosity emanations of (normally) electromagnetic waves coming from the centre of galaxies. Sometimes the ejection from an AGN points towards Earth, making it look very bright (we call it a ‘blazar’). It has been suggested that streams of plasma emanating from AGN’s can interact (somehow) with pulsars (another type of neutron star, highly magnetized and rotating) to produce FRBs. Indeed, previously, a faint gamma-ray burst was observed coinciding with an FRB and may eventually help explain the origin of FRBs.
So that’s a brief journey through some high energy astrophysics terminology (!): gamma-ray bursts (most energetic explosions in the universe, from supernovae), active galactic nuclei, quasars, blazars, magnetars, pulsars, FRBs, neutron stars, etc. (more on these another time).
But no one yet knows why FRB’s are only momentary and seem not to appear again. Perhaps more time is needed to see if repeated FRB’s are more common than previously thought, or a signature of some new interesting phenomenon in astrophysics. Will it happen again… “the answer is definitely maybe”!