Mysterious bursts of radio waves identified far outside galaxy
- July 16, 2014
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Mysterious split-second pulses of radio waves are coming from deep in outer space, and nobody knows what causes them, according to astronomers.
Researchers led by Laura Spitler from the Max Planck Institute for Radio Astronomy in Bonn, Germany say they have found the first so-called “fast radio burst” in the sky's northern hemisphere, using the Arecibo radio telescope in Puerto Rico.
The mystery is reminiscent of that of gamma-ray bursts, discovered in the 1960s and now thought to come from giant stars collapsing to form black holes. The new phenomenon, in the form of radio rather than gamma-rays-a different form of light-remains an enigma.
The flashes last only a few thousandths of a second. Scientists using the Parkes Observatory in Australia had recorded such events before, but the lack of similar findings by other telescopes led to speculation that the Australian instrument might have been picking up signals from sources nearby Earth.
The finding at Arecibo is the first detection using a different telescope: the burst came from the direction of the constellation Auriga in the Northern sky, according to the scientists, who detail their findings July 10 in the online issue of The Astrophysical Journal.
“There are only seven bursts every minute somewhere in the sky on average, so you have to be pretty lucky to have your telescope pointed in the right place at the right time,” said Spitler, the paper's lead author. “The characteristics of the burst seen by the Arecibo telescope, as well as how often we expect to catch one, are consistent with the characteristics of the previously observed bursts from Parkes.”
“The radio waves show every sign of having come from far outside our galaxy – a really exciting prospect,” added Victoria Kaspi of the McGill University in Montreal and principal investigator for the pulsar-survey project that detected the burst
Possible causes, scientists said, 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 pulse was detected on Nov. 2, 2012, at Arecibo, with the world's largest and most sensitive single-dish radio telescope.
The result confirms previous estimates that the bursts occur roughly 10,000 times a day over the whole sky, said the astronomers, who inferred the huge number by calculating how much sky was observed, and for how long, to make the few detections so far reported.
The bursts appear to be coming from beyond the Milky Way galaxy based on measurements of an effect known as plasma dispersion. Pulses that travel through the cosmos are distinguished from man-made interference by the effect of electrons in space, which cause longer radio waves to travel more slowly.
Source : http://www.world-science.net