More puzzling radio bursts from deep space
Astronomers have detected very fast bursts of radio waves coming from deep in outer space and they don’t know the source.
Scientists initially detected the pulses at the Parkes Observatory in Australia, but the bursts were not confirmed by another radio telescope facility until now.
A team at the Arecibo Observatory in Puerto Rico detected the pulse on November 2, 2012. Arecibo boasts the world’s largest and most sensitive radio telescope, with a radio-mirror dish spanning 305 meters and covering about 20 acres.
“Our result is important because it eliminates any doubt that these radio bursts are truly of cosmic origin,” says Victoria Kaspi, an astrophysics professor at McGill University in Montreal and principal investigator for the pulsar-survey project that detected this fast radio burst.
“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.
“Another possibility is that they are bursts much brighter than the giant pulses seen from some pulsars,” notes James Cordes, a professor of astronomy at Cornell University and coauthor of the new study published in the Astrophysical Journal.
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 confirm 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,” says Laura Spitler, lead author of the new paper. Spitler, now a postdoctoral researcher at the Max Planck Institute for Radio Astronomy in Bonn, Germany, was a PhD student at Cornell when the research work began.
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 human-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 scientists report.
The discovery was made as part of the Pulsar Arecibo L-Band Feed Array 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.
Efforts are now under way to detect radio bursts using radio telescopes that can observe broad swaths of the sky to help identify them. Telescopes under construction in Australia and South Africa as well as the CHIME telescope in Canada have the potential to detect fast radio bursts; astronomers say these and other new facilities could pave the way for many more discoveries and a better understanding of this mysterious cosmic phenomenon.
Grants from the European Research Council, the National Science Foundation, the Natural Sciences and Engineering Research Council of Canada, the Fonds de recherche du Québec-Nature et technologies, and the Canadian Institute for Advanced Research, among others funded the work.
Source: McGill University