A burst of cosmic radio waves has finally been traced back to its source: an old dwarf galaxy located more than 3 billion light years from Earth.
Such bursts are rare and last only briefly, but have been of interest since their first detection almost ten years ago due to their appearance from outside our galaxy.
Fast radio bursts flash for just a few milliseconds and need to be very powerful in order to be observed from Earth. Combined with their origin being outside our galaxy, the fact that none of those originally observed were detected again has led to such bursts causing great interest in the astronomical community.
A repeating burst discovered in 2012 allowed researchers to monitor its area of the sky with the Karl Jansky Very Large Array (VLA) in New Mexico and the Arecibo radio dish in Puerto Rico.
The development of high-speed data recording and real-time data analysis software by an astronomer at the University of California, Berkeley, allowed the VLA to detect a total of nine bursts over the period of a month last year.
The VLA’s detection pinpointed the burst to within a tenth of an arcsecond, subsequent efforts by larger European and American radio interferometer arrays further narrowed it to within one-hundredth of an arcsecond, within a region about 100 light years in diameter. Deep imaging by the Gemini North Telescope followed and revealed an optically faint dwarf galaxy that the VLA found to continuously emit low-level radio waves.
This emission is typical of a galaxy with an active nucleus perhaps indicative of a central supermassive black hole. It is also noted that extremely bright exploding stars – called superluminous supernovae – and long gamma ray bursts also occur in this type of galaxy. Both such events are believed to be associated with the massive, highly magnetic and rapidly rotating neutron stars called magnetars.
“All these threads point to the idea that in this environment, something generates these magnetars,” said co-author and UC Berkeley astronomer Casey Law.
“It could be created by a superluminous supernova or a long gamma ray burst, and then later on, as it evolves and its rotation slows down a bit, it produces these fast radio bursts as well as continuous radio emission powered by that spindown. Later on in life, it looks like the magnetars we see in our galaxy, which have extremely strong magnetic fields but rotate more like ordinary pulsars.”
Law’s theory is but one, though the new data has ruled out several explanations for the origin of the radio bursts that had previously been offered. Law’s team are the first to observe the bursts as a cosmological phenomenon and where said phenomenon is occurring; the objective now is to figure out the reason for the phenomenon’s occurrence.