The finding by an international team of astronomers marks the first time that a so-called “fast radio burst” has been detected using an instrument other than the Parkes radio telescope in Australia. Scientists using the Parkes Observatory have recorded a handful of such events, but the lack of any similar findings by other facilities had led to speculation that the Australian instrument might have been picking up signals originating from sources on or near Earth.
“Our result is important because it eliminates any doubt that these radio bursts are truly of cosmic origin,” said Victoria Kaspi from McGill University in Montreal. “The radio waves show every sign of having come from far outside our galaxy — a really exciting prospect.”
Exactly what may be causing such radio bursts represents a major new enigma for astrophysicists. Possibilities include a range of exotic astrophysical objects, such as evaporating black holes, mergers of neutron stars, or flares from magnetars — a type of neutron star with extremely powerful magnetic fields.
“The race is now on to figure out what causes these bursts. If they really originate from outside the Milky Way, that would be extremely exciting,” said Jason Hessels from the University of Amsterdam.
The unusual pulse was detected November 2, 2012, at the Arecibo Observatory, a National Science Foundation-sponsored facility that boasts the world’s largest and most sensitive radio telescope with a radio-mirror dish spanning 1,000 feet (305 meters) and covering about 20 acres.
While fast radio bursts last just a few thousandths of a second and have rarely been detected, the international team of scientists reporting the Arecibo finding confirms previous estimates that these strange cosmic bursts occur roughly 10,000 times a day over the whole sky. This astonishingly large number is inferred by calculating how much sky was observed and for how long in order to make the few detections that have so far been reported.
“The brightness and duration of this event, and the inferred rate at which these bursts occur are all consistent with the properties of the bursts previously detected by the Parkes telescope in Australia,” said Laura Spitler from the Max Planck Institute for Radioastronomy in Bonn, Germany.
The bursts appear to be coming from beyond the Milky Way Galaxy based on measurement of an effect known as plasma dispersion. Pulses that travel through the cosmos are distinguished from man-made interference by the effect of interstellar electrons, which cause radio waves to travel more slowly at lower radio frequencies. The burst detected by the Arecibo telescope has three times the maximum dispersion measure that would be expected from a source within the galaxy.
The discovery was made as part of the Pulsar Arecibo L-Band Feed Array (PALFA) survey, which aims to find a large sample of pulsars and to discover rare objects useful for probing fundamental aspects of neutron star physics and testing theories of gravitational physics.
“It’s fantastic that the PALFA survey is discovering not just pulsars, but also other powerful bursts of radio radiation,” said Joeri van Leeuwen from the University of Amsterdam.
Efforts are now underway to use the Low Frequency Array (LOFAR) and the upgraded Westerbork/Apertif telescope to observe broad swaths of the sky and detect more fast radio bursts. Hessels and Van Leeuwen expect many more discoveries and a better understanding of this mysterious cosmic phenomenon.
