Astronomy
spectively look at the whole sky)
means that it is ideal for carrying out
surveys and monitoring very short-lived phenomena. These include
supernovae explosions and the consumption of companion stars by supermassive black holes. The telescope
will also be used to study the solar
wind, the structure and evolution of
cosmic magnetism, and ultra-high-energy cosmic rays via the radio emission produced by showers in the
Earth’s atmosphere.
The computing and data-transport
power of the facility might also be
used in more down-to-Earth applications by attaching other instruments
to the array. For example, a set of geo-phones will be used to carry out seismic imaging of the way the low-lying
Netherlands is sinking due to natural
gas being pumped out of the ground.
Namir Kassim, a radio astronomer
at the Naval Research Laboratory in
Washington, DC, who was project
scientist for LOFAR in its previous
incarnation, is confident that the
facility will do valuable science. “The
low-frequency end of the radio spectrum is so poorly explored that it
is quite a safe bet that LOFAR will
lead to important new discoveries for
astrophysics,” he says. That sentiment is echoed by Philip Diamond,
director of Jodrell Bank, who regards
LOFAR as “an instrument that has
been designed to do science we may
not yet have thought of”.
Five stations have now been completed in Germany and the Netherlands. The first interferometric fringes
have since been produced and Garrett
says that the vast majority of the Dutch
and European stations should be complete by the time of the formal opening of the facility, which is scheduled
for June next year.
But Diamond warns that getting
LOFAR fully up and running will be a
challenge. “The team has needed to
develop techniques to deal with radiofrequency interference, and the researchers will also have to cope with
the solar maximum predicted for 2013
and the resultant disruption to the
ionosphere,” he says. “They are also
going to test the new computational
techniques to their limit.” Still, Diamond adds that this experience should
prove valuable in the construction of
radio astronomers’ next hoped-for
monster telescope, the Square Kilometre Array (see right). As its name
suggests, this facility would use detectors with a combined area of a square
kilometre, an undertaking that is likely
to cost at least $1.5bn. LOFAR, in
comparison, will be a snip.
Australia has opened one new astronomy
centre and announced plans for another
as part of the country’s bid to host the
Square Kilometre Array (SKA) radio
telescope. The A$100m International
Centre for Radio Astronomy Research
(ICRAR) in Perth, Western Australia,
was formally opened last month, while
a planned A$80m high-performance
computing centre nearby will serve
SKA-related projects and others in the
physical sciences. The two facilities are
designed to help realize SKA and also
boost Australia’s chances against a rival
South Africa-led proposal to host it.
The SKA concept is based on an array
of 2000–3000 linked antennas, which
will be scattered from a central “core” to
remote stations, giving the array the
same collecting area as a hypothetical
1 km-diameter steerable dish. Key
scientific challenges include designing
the antennas and developing the
computing capacity to handle the
terabytes of data that both SKA and
smaller prototype arrays – known as
“pathfinders” – will generate.
Steven Tingay, ICRAR’s deputy director,
says that projects at the new centre will
include designing and testing arrays of
all-electronic telescopes like those
planned for SKA. The centre will also
provide operational support for the
New labs boost Australian array bid
Medical physics
CSIRO
Murchison radio-astronomy observatory,
which will form the “core” of Australia’s
SKA bid, and where installation of a
pathfinder array, known as ASKAP, is
scheduled to begin later this year.
The centre is being funded by the
West Australian state government and
the universities of Western Australia
and Curtin, and will eventually employ
50–60 staff, including international
collaborators, Tingay says.
The computing centre, meanwhile, is
to be supported by federal funds. Named
after Australian radio-astronomy pioneer
Joe Pawsey, it will be open to all
Australian researchers requiring access
to supercomputing resources. Initially,
however, its main focus will be the signal-processing tasks associated with ASKAP
and another radio-astronomy facility, the
Murchison Widefield Array, which is
currently under construction.
Meanwhile, New Zealand has formally
joined Australia’s SKA bid, raising the
possibility that up to 20 antennas could
be built on the country’s North and South
Islands, some 5000 km away from the
candidate core site in Western Australia.
Such a long “baseline” would boost an
Australia-based telescope’s ability to
resolve distant objects.
Peter Pockley
Sydney
Looking up
An artist’s impression
of the ASKAP
pathfinder array at
the Murchison
Radio-Astronomy
Observatory.
Study warns of radiation risk in medical imaging
A study of a million US patients suggests that some who undergo medical
imaging could be exposed to more
ionizing radiation than those who
work with radioactive materials in
nuclear power plants. The study, reported in The New England Journal
of Medicine (361 849), implies that
current exposure to radiation from
conventional X-ray equipment as well
as computed tomography (CT) and
positron-emission tomography (PE T)
scanners could lead to tens of thousands of extra cases of cancer in the
US alone.
The study was carried out by a team
led by cardiologist Reza Fazel of
Emory University, who used data
from insurance claims to identify the
number and types of procedures that
patients underwent between 2005
and 2007. The team then estimated
individuals’ exposure to ionizing radiation based on the effective doses as-
If a procedure
is used
appropriately,
then the benefit
far outweighs
any risk
from ionizing
radiation
sociated with the procedures.
The data revealed that 0.2% of the
patients received an annual dose of
more than 50 mSv – equal to the limit
for occupational exposure to workers
in nuclear power plants and other
sources of ionizing radiation. The
authors suggests that, generalizing the
results to the entire US population,
about 400 000 adults could be exposed
to such a high dose; whereas four million could receive annual doses above
20 mSv – the occupational limit for
airline crews.
Brahmajee Nallamothu of the University of Michigan, a co-author of
the paper, notes, however, that the
risk to any individual for a single test
may be small. “If a procedure is used
appropriately, then the benefit far
outweighs any risk from ionizing radiation,” adds Fazel.
Peter Gwynne
Boston, MA
