The Mysterious

The Mysterious
Origins of Fast
Radio Bursts
With the discovery of fast radio bursts,
astronomers once again navigate the path from
weird result to verified science.
By Yvette Cendes | Thursday, April 30, 2015
RELATED TAGS: PHYSICS
Parkes Observatory
Shaun Amy/CSIRO/NASA/JPL
Duncan Lorimer will never forget the
moment he stumbled upon one of the
great new mysteries in astronomy. The
English radio astronomer at West

Virginia University had asked an
undergraduate, David Narkovic, to comb
through pulsar survey data from the
Parkes Observatory in Australia. One
fateful day in 2006, Narkovic walked into
Lorimer’s office with evidence of an
unusual observation: a pulse of radio
waves from the sky unlike any seen
before. It was among the brightest
observations ever in radio astronomy,
originating from billions of light-years
away, and it lasted just a few
milliseconds. “I was speechless,” Lorimer
recalls. “To be honest, I didn’t know
what to make of it.”
Lorimer and Narkovic had uncovered
the first fast radio burst, or FRB. It was a
total surprise to them; the idea of radio
wave bursts had been abandoned after
scientists in the ’70s and ’80s failed to
locate such signals. Only a handful of
them (11 at last count) have been
observed since their discovery nine
years ago, and they remain unique.
Many astronomers think they come from
outside the galaxy, but beyond that, their
origins remain mysterious. As novel as
FRBs are, however, they are just the
latest example of a sporadic but always
exciting moment in science: an
unexpected discovery of an anomaly in
the expected data.
Anomaly Analysis
Although each unusual scientific
discovery is unique, different disciplines
of science process these anomalies
similarly. The physicist and philosopher
of science Thomas Kuhn first advocated
the importance of such unexpected
discoveries in the 1960s. Scientific
progress is not a linear development of
accepted theories, he argued, but instead
relies on such anomalous discoveries to
move the field forward. When enough
accumulate from experiments, a field
will enter a period of crisis, which often
leads to a fundamentally new
understanding of the field, known as a
paradigm shift. Science is filled with
examples of paradigm shifts throughout
its history, such as the switch from
Newtonian to Einsteinian physics, the
rise of evolution to account for the
variety of life and the acceptance of
plate tectonics to explain the movement
of continents over time.
In astronomy, paradigm shifts typically
come from an unexpected signal in the
sky. Steady pulses in the 1960s yielded
the unexpected discovery of pulsars —
the city-size neutron stars that Lorimer
sought when he stumbled upon FRBs.
Similarly, gamma ray bursts can
originate from among the most violent
events in the universe, such as the
collapse of a massive star, but they were
only serendipitously discovered by
researchers monitoring nuclear
proliferation on Earth during the Cold
War.
Kuhn revolutionized how scientific
anomalies are viewed today, but it’s still
not so simple. “Most historians and
philosophers of science, although they
like the thrust [of Kuhn’s argument],
don’t buy it all,” says Alan Rocke, a
science historian at Case Western
Reserve University in Cleveland. “There
are still many disagreements about the
details.” In reality, history is far messier.
Some paradigm shifts take a long time
before a theoretical framework emerges,
and sometimes anomalies lie dormant
for decades or even centuries before
being accepted and changing the course
of science. Critical scholars argue that a
Kuhnian world defined by sudden shifts
is too simplistic, and that in reality
things play out differently under
different circumstances.
The first fast radio burst jumped out from the
data at researchers, who struggled to explain it.
Duncan Lorimer/West Virginia University
Kuhn’s view also can leave too casual an
impression of scientific progress. Look
no further than the term paradigm shift
becoming a corporate buzzword with
little nonscientific meaning. Rocke
emphasizes that serendipitous
discoveries do not just pop out of
nowhere. “It’s similar to what Louis
Pasteur said: ‘Chance favors the
prepared mind,’ ” he says. The
discoveries of super glue, Teflon and
saccharine are all “lucky breaks” that
actually came from determined chemists
in the laboratory. “If you find something
odd, it usually happens when you are
obsessively engaged,” Rocke says. “You
are focused, you are fiddling, and you
only notice because you know what
should happen.”
And indeed, that first “Lorimer burst,”
as it was known before the discovery of
other FRBs, may have gone unnoticed if
he hadn’t been deeply interested. But
which way would this anomalous signal
go? Was it the first step on the path to a
paradigm shift in radio astronomy,
similar to pulsars or gamma ray bursts?
Or were Lorimer bursts a dead end?
From Error to Anomaly
Lorimer soon enlisted friend and
collaborator Matthew Bailes, a pulsar
astronomer at Swinburne University of
Technology in Melbourne, to help make
sense of that one FRB. Bailes’ inclusion
resulted in new insights on the pulse’s
shape, its evolution over time and the
vast, extragalactic distance it overcame.
Bailes even secured additional observing
time at Parkes Observatory for follow-up
observations. Even after a week combing
the original spot in the sky that first FRB
came from, they couldn’t find any other
signals.
A second FRB remained elusive for years,
both at Parkes and other observatories,
leading many astronomers to speculate
whether the FRB anomaly was real. One
particular concern was that the FRB
might have originated from nearby
thunderstorms, a particularly mundane
explanation. Further, radio astronomy is
a field with several cases of unexplained
anomalous signals. For example, 1977’s
“Wow!” signal was a one-time radio
burst lasting several minutes that bore
the profile of a potential signal from
extraterrestrials (hence its designation,
coming from an excited researcher’s
notes). But no such signal was ever
observed again. Without further
observations, it is impossible for
astronomers to classify it as anything
more than a meaningless anomalous
signal.
Eventually, patient searching did yield
other FRBs, and astronomers slowly
began to take them seriously as a
scientific phenomenon. The biggest
hurdle at this point was that only one
observatory, Parkes, had ever seen the
flashes. Without a second telescope’s
observation, it meant FRBs could still be
nothing but human interference or a
local atmospheric phenomenon rather
than a new discovery in radio
astronomy. After all, in Kuhn’s
framework, an anomaly is a problem
without explanation; knowing an FRB
from Parkes could just be local
interference kept FRBs at the non-
anomaly stage.
The clincher arrived in early 2014 when
a team at Arecibo Observatory in Puerto
Rico announced they’d seen an FRB.
That two telescopes on opposite sides of
the planet observed the same
phenomenon won over many skeptics.
“We now know it’s not a farmer’s
electric fence,” Bailes dryly observed,
“unless they maybe have the same model
fence in Arecibo.” FRBs finally entered
new scientific territory: an anomaly
looking for an explanation.
Seeking the Answer
Now that FRBs have crossed over from
strange oddity to real discovery,
speculation has also ramped up on what
creates them. “There are more ideas
than bursts,” explains Lorimer.
Proposals have ranged from stars
shooting off enormous flares from their
outer atmospheres to overactive
magnetars — dense stellar remains with
extremely powerful magnetic fields —
but astronomers are hampered by an
inherent imprecision with radio
telescopes making it difficult to pinpoint
a source. Lorimer’s favorite idea has
FRBs result from neutron stars colliding
together far beyond our galaxy. “I have
no support for that beyond romantic
beliefs,” he confesses. As a pulsar
astronomer, he admits he is “a little
biased” toward explanations involving
them.
As the evidence and observations of
these FRB anomalies continue to trickle
in, however, astronomers are cautiously
optimistic that they have stumbled not
across fiction or technical error, but
something much more novel. “It has
been exciting to see it go from an oddity
to something tangible,” Lorimer says. It’s
a journey familiar to much of science.
[This article originally appeared in print
as "Anomaly From Above."]