The radio bursts are energetic enough to suggest that they are triggered by extremely powerful astrophysical events. Evaporating black holes or supernovae might be possible sources.
This illustration shows the Parkes radiotelescope with a 'radio burst' flashing in the sky. The red background is gas in our galaxy.
Swinburne Astronomy Productions, vr.swin.edu.au
EnlargeAstronomers have discovered four mysterious radio bursts from beyond the Milky Way, bursts unlike any in the catalog of emissions from well-known radio sources in space or on Earth.
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E.T. is an unlikely source, since each burst seems to be a one-off event. Instead, what little evidence astronomers have in hand suggests that the bursts come from astrophysical sources billions of light-years away. The bursts are energetic enough to suggest that they are triggered by extremely powerful astrophysical events.
These fast radio bursts last a few thousandths of a second and slide ever lower in frequency as they fade.
Based on the number of events that the researchers detected in their hunt for the bursts, roughly 10,000 of these should appear across the sky each day ? or one every nine to 10 seconds, they say.
"If we could view the sky with 'radio eyes' there would be flashes going off all over the sky every day," said Michael Kramer, director of the Max Planck Institute for Radio Astronomy in Bonn, Germany, and a member of the team reporting its results in Friday's issue of the journal Science.
So far, no one has been able to associate any of these with a particular galaxy, presuming that they have galactic sources. Indeed, once one tries to go beyond the generalization of "exotic sources" for these radio bursts, speculation varies widely on their cosmic transmitters, according to James Cordes, a radio astronomer at Cornell University in Ithaca, N.Y.
Evaporating black holes, supernovae, merging neutron stars, or neutron stars with unusually strong magnetic fields compared with other neutron stars all could be possible sources, Dr. Cordes writes in a commentary in Science tied to the new discovery.
But he also cautions patience, noting it took 20 years for astronomers to uncover the sources of gamma-ray bursts, first detected not by astronomers but by satellites designed to spot above-ground nuclear explosions. Only after astronomers began hunting for the gamma-ray bursts and performing near-instant follow-ups with telescopes operating at other wavelengths were they able to uncover the exotic events that triggered the bursts.
The same is likely to hold true for fast radio bursts, he writes.
This is actually the second reported detection of these unique cosmic signals.
In 2007, a team led by Duncan Lorimer, astrophysicist at West Virginia University in Morgantown, reported the first such burst detected, based on a review of 6-year-old data captured by the 210-foot-diameter radio telescope at the Parkes Observatory in Australia. The team put the source's location in the vicinity of the Large Magellanic Cloud, one of the Milky Way's satellite galaxies.
But the burst appeared far enough away from the satellite galaxy to suggest an origin beyond the Milky Way's neighborhood. Indeed, the team estimated, the source of the burst was some 3 billion light-years away.
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