http://www.skyandtelescope.com.au 21SKA SOUTH AFRICA
and 135 times faster survey speed than LOFAR, SKA1-low is
poisedtofinallysolvetheriddleofcosmicdawn:whenand
howthecosmicdarkagescametoanend,andwhatkindof
objects — massive stars or fledgling quasars — were the first to
make the universe shine. Similar observations will be carried
out in South Africa’s Great Karoo by the HERA telescope
(Hydrogen Epoch of Reionisation Array), which is the fourth
andfinalSKAprecursorinstrument.Nextyear,HERAwill
comprise some 350 simple stationary wire-mesh dishes, each
14 metres across and sitting shoulder-to-shoulder to catch
low-frequency radio waves from the zenith.
By the end of this year, the detailed design and theconstruction proposal for the first phase of the Square
Kilometre Array will be completed. Diamond expects
constructiontostartnextyear.Infact,thefirst12-metre
antenna has already arrived on site in South Africa.
“We’ll have early science results in 2021, and SKA1 will
befullyoperationalin2024,”Diamondsays.“It’sahuge
challenge. We’re developing and constructing something no
one has ever built before.” Asked about the prospects for the
second phase of the project, the SKA director admits that
none of the 12 member countries has committed themselves
to building SKA2 yet. “There’s always the risk of cancellation,
but it doesn’t particularly keep me awake at night,” he says.
Nor me. Whatdoeskeep me awake, both in the South
African Karoo and in the Australian outback, is the
unbelievable view of the star-studded night sky—auniverse
filled with wonder. Ten years from now, many outstanding
cosmic mysteries may have been solved by the sheer power
of humankind’s largest and most sensitive astronomical
observatory ever. And there’s little doubt that the Square
KilometreArray—evenifonlyphase1willeverberealised
— is going to present us with a lot of scientific surprises,
too. Says Diamond: “When the Hooker telescope on Mount
Wilson started operations in 1917, no one expected the
discoveryoftheexpansionoftheuniverse.Ihavereallyno
idea what the SKA will be famous for a century from now.”S&TContributingEditorGOVERT SCHILLINGlives in the
Netherlands but enjoys visiting astronomical facilities all over
the world. In August 2017 Harvard University Press will publish
his new book,Ripples in Spacetime: Einstein, Gravitational
Waves, and the Future of Astronomy.WHAT SQUARE KILOMETRE?
The Square Kilometre Array is named after the planned
total collecting area of its second phase (SKA2).
However, the first phase of the project (SKA1) will be
much smaller. SKA1-mid, conmprising a couple of
hundred dishes in South Africa, will end up with a total
collecting area of some 33,000 m^2 (0.033 km^2 ); SKA1-
low, in Australia, will have a collecting area of 0.4 km^2 ,
basically due to the large concentration of antenna
fields in the core region of the array (so the collecting
area won’t grow by a factor of ten when SKA2 is
realised). Combined, SKA1 will have a collecting area
of less than half a square kilometre. For comparison:
the recently completed Chinese Five-hundred-metre
Aperture Spherical Radio Telescope (FAST), the largest
single-dish instrument in the world, has a collecting
area of 0.2 km^2.SHERA One of four SKA precursor projects,
HERA detects radio signals from neutral hydrogen, studying the large-scale
cosmic structure that existed before and during the Epoch of Reionisation.