The Square Kilometre Array
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For the past ten years, astronomers from 17 countries have
been contemplating the next big step forward in our understanding
of the Universe. So far, our telescopes have probed back in time
to a period when the Universe was about 1/10 of its current age.
At that time, stars, planets and galaxies were already formed. To
understand how these objects were formed, we need to look back to
a time before there were stars and galaxies, when the Universe
consisted of only a dark void of Hydrogen gas. In this cosmic
Dark Age, the first stars formed and the first light shone in the
Universe – the cosmic dawn. To capture this moment, we will
need to build a telescope that can detect the weak signals coming
from Hydrogen gas emitted at a time when the Universe was in the
first 1% of its life. Such a telescope will have to work in the
radio part of the spectrum and have a collecting area of around 1
million square metres, about 50 times larger than anything that
exists today. This Square
Kilometre Array (SKA) will also need receiving dishes spread
out over distances of more than 3000 km to accurately capture the
images of the first stars and galaxies.
The radio signals from the cosmic dawn will reach the Earth at
a frequency in the FM part of the radio spectrum. This piece of
the radio band is completely saturated with man-made signals over
most of the Earth’s inhabited regions. To avoid this
interference, the new telescope will have to be placed in a
remote location, yet still be accessible to astronomers and
engineers from around the world. An international search for such
a location has shown that the Midwest of Western Australia is the
most radio quiet region on Earth. The vast extent of the
Australia continent also allows for the positioning of dishes
over the thousands of kilometres needed to discovery the sources
of the first light. The remote desert of WA, home to Aboriginal
peoples who were arguably the world’s first astronomers,
may provide mankind with its clearest view of the first objects
created – the seeds of the Universe we see around us
today.
The Murchison Radio-astronomy Observatory (MRO) is situated on a 350,000 hectare cattle and sheep
station, 300 kilometres north east of Geraldton in the classical
Australian landscape of flat red plains and deep blue skies. The
historic (circa 1850) property has been chosen by researchers
from Australia, the US and Canada to build a $100m
“pathfinder” radio telescope array with a size of
about 1% of the final SKA. Over the next three years, the
pathfinder will test out the new technologies needed to build the
SKA, establish the quality of the site for astronomy and make its
own contributions to radio astronomy as a new unique instrument.
By the end of 2010, government agencies and astronomers from the
17 countries involved in the SKA will make a final decision on
the site to build the $1.8 billion SKA. Australia and South
Africa are currently in an international competition to host the
largest telescope ever built.
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