“Viewing”
Radio
Waves
in Colour
By
Ross Tester
from billions of years ago
Imagine if you were able to “see” radio waves as they traversed the
huge distances of space. A research team is using a new array in the
Western Australian desert to not only view radio waves but assign
them colours.
T
o most people in radio and
electronics, frequencies above
50MHz are regarded as very
high; indeed, by definition the VHF
spectrum starts at 30MHz, with the
Ultra High Frequency bands starting
at 300MHz.
To astro-physicists, 50-350MHz are
regarded as low frequencies but are
an increasingly important spectrum
26 Silicon Chip
with a large amount of research into
this band being done at installations
around the world.
By capturing the unbelievably feint
radio signals emitted by stars and other celestial bodies at the far reaches of
our (Milky Way) galaxy and beyond,
they’re looking for clues into how
those bodies began – countless millions (or billions) of years ago – long
before our Earth had evolved.
Here in Australia, the focus of such
research is the Murchison Widefield
Array or MWA, (a tiny section of which
is shown above). This $50 million radio telescope is located at a remote
site northeast of Geraldton, Western
Australia.
The MWA observes low-frequency
radio waves (between 70 and 320 MHz)
siliconchip.com.au
and was the first of the three Square
Kilometre Array (SKA) precursors
to be completed.
A consortium of 13 partner institutions from four countries (Australia, USA, India and New Zealand) has financed the development, construction, commissioning
and operations of the facility. Since
commencing operations in mid
2013 the consortium has grown to
include new partners from Canada
and Japan.
Key science for the MWA ranges
from the search for red-shifted HI
(neural hydrogen) signals from the
Epoch of Reionisation to wide-field
searches for transient and variable
objects (including pulsars and fast
radio bursts), wide-field galactic
and extra-galactic surveys, plus solar and heliospheric science.
Colour views
The research is being led by Dr
Natasha Hurley-Walker, of Curtin
University (Perth) and the International Centre for Radio Astronomy
Research (ICRAR). What makes Dr
Hurley-Walker and her team’s research of interest to much more
than the radio astronomy community is their cataloging of 300,000
galaxies in glorious living colour
– in other words, what the human
eye would “see” if it could indeed
view radio waves.
It’s given the moniker of “GLEAM”
– GaLactic and Extra-galactic Allsky MWA. In other words, the Murchison radio telescope is not simply
looking into the far-flung reaches of
our own Milky Way galaxy, it’s looking far beyond, to the limit of currently available technology.
Normally a radio wave would
just be noted as that – a radio wave,
with a certain frequency and perhaps some unusual characteristics.
“The human eye sees by comparing brightness in three different primary colours – red, green and blue,”
Dr Hurley-Walker said. “GLEAM
does rather better than that, viewing the sky in 20 primary colours.”
“That’s much better than we humans can manage and it even beats
the very best in the animal kingdom, the mantis shrimp, which can
see 12 different primary colours,”
she said.
GLEAM is a large-scale, high-resolution survey of the radio sky, obsiliconchip.com.au
serving radio waves that have been
travelling through space – some for
billions of years. The more distant
the source of the radio waves, the
longer they have taken to get to Earth
and be detected
“Our team is using this survey to
find out what happens when clusters of galaxies collide,” Dr HurleyWalker said.
“We’re also able to see the remnants of explosions from the most
ancient stars in our galaxy, and find
the first and last gasps of supermassive black holes.”
GLEAM is one of the biggest radio surveys of the sky ever assembled, with an enormous area of the
sky being scanned.
Large sky surveys like this are extremely valuable to scientists and
they’re used across many areas of
astrophysics, often in ways the original researchers could never have
imagined.
Completing the GLEAM survey
with the MWA is a big step on the
path to SKA-low, the low frequency
part of the international Square Kilometre Array (SKA) radio telescope
to be built in Australia in the coming years.
The SKA
The Square Kilometre Array project is an international effort to build
the world’s largest radio telescope,
led by SKA Organisation based at
the Jodrell Bank Observatory in
England.
Co-located primarily in South Africa and Western Australia, the SKA
will be a collection of hundreds of
thousands of radio antennas with a
combined collecting area equivalent
to approximately one million square
metres, or one square kilometre.
The SKA will conduct transformational science to improve our
understanding of the Universe and
the laws of fundamental physics,
monitoring the sky in unprecedented detail and mapping it hundreds of times faster than any current facility.
(SILICON CHIP featured the SKA
project in the December 2011 issue
and again in the July 2012 issue).
Acknowlegement: Much of the information in this feature came courtesy of Dr Natasha Hurley-Walker
and the GLEAM team. (See www.
icrar.org/gleam).
Ever wondered what radio waves from space
would look like if you could see them? Try
the applet http://gleamoscope.icrar.org/ These
views are of the same section of sky, through
the Milky Way galaxy and beyond.
SC
January 2017 27
