Space Briefs
Radio bursts discovered
from beyond our galaxy
Astronomers, including a team member from NASA’s Jet Propulsion
Laboratory in Pasadena, Calif., have detected the first population of
radio bursts known to originate from galaxies beyond our own Milky
Way. The sources of the light bursts are unknown, but cataclysmic
events, such as merging or exploding stars, are likely the triggers.
A radio burst is a quick surge of light from a point on the sky, made
up of longer wavelengths in the radio portion of the light spectrum. A
single radio burst was detected about six years ago, but researchers
were unclear about whether it came from within or beyond our galaxy.
The new radio-burst detections -- four in total -- are from billions of
light-years away, erasing any doubt that the phenomenon is real. The
discovery, described in the July 4 issue of the journal Science, comes
from an international team that used the Parkes Observatory in Australia.
“Short radio bursts are really tricky to identify,” explained Sarah Burke
Spolaor of JPL. “Our team had to search 11 months of data covering a
large sky area to find them.”
Spolaor developed the software used to seek single pulses in the
radio data and pick out genuine signals from local interference sources
-- such as cell phones, spark plugs and aircraft. This amounted to an
enormous and complex computational task.
Dan Thornton, lead author of the new study from England’s University
of Manchester and Australia’s Commonwealth Scientific and Industrial
Research Organization, said, “The radio bursts last for just a few
milliseconds and the farthest one that we detected was 11 billion lightyears away.”
The findings open the door to studying an entirely new class of
eruptive cosmic events and can also help with cosmology mysteries,
for example, about the nature of matter in the universe.
Our sky is full of flares and bursts of varyi ng natures. For instance,
gamma-ray bursts are thought to occur when stars collapse into black
holes. They are routinely detected by a network of telescopes on the
ground and in space, including NASA’s Swift and Fermi. When one
telescope in the network detects a burst, it can notify others to quickly
slew to the target for coordinated observations.
The newfound radio bursts, while likely of a different origin than
gamma-ray bursts, also consist of light waves generated by powerful
events happening at great distances. Researchers would like to develop
systems similar to the gamma-ray burst networks of telescopes to follow
up quickly on radio bursts, but this is more challenging because radio
waves are slowed by gas in space. Time is needed to process the radio
observations and tease out the short-lived bursts.
On the other hand, the fact that radio waves are impeded as they
travel through space to reach us offers benefits. By studying how the
radio waves have been slowed, scientists can better understand
baryonic matter, the material that gets in the way. Baryonic matter is
what makes up people and planets and everything you see. The rest of
the universe consists of mysterious substances called dark matter and
dark energy.
Exactly what is triggering the release of the radio waves is unknown.
Theories include colliding neutron stars or black holes; evaporating black
holes; and stellar explosions called supernovae. The new data do not
fit nicely with any of these scenarios, leaving the scientists perplexed.
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