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Mapping the universe with a split SKA

Submitted by Kevin Jardine on 25 May, 2012 - 17:47

The biggest astronomy news today is not the Dragon docking (though that is a great bit of technology), but the decision to split the giant Square Kilometre Array radio telescope between South Africa and Australia / New Zealand.

The current news stories about this (to its credit, BBC made SKA its lead story) are a bit vague about the implications beyond political buy-in and increasing the cost by about 10%.

The decision was unexpected but is great news for science for at least one major reason: astrometry.

A paper published in 2004 by Ed Fomalont and Mark Reid, Microarcsecond astrometry using the SKA, recommended that the giant radio telescope array be distributed over about 5000 km because such a large radio baseline would allow much more accurate measurements of the positions of the objects it studies.

Splitting SKA between Australia / New Zealand and South Africa produces a baseline even longer than that - more than 10 thousand kilometres.

As explained in this article on parallax, by measuring the tiny shifts in the position of an object in the sky as the Earth orbits the Sun, astronomers can determine its distance.

Distance measurements are essential in mapping the Milky Way and the universe as a whole.

The 2004 article goes on to point out the enormous baselines possible with orbiting radio telescopes (perhaps a 100 thousand kilometres). I suspect that with such huge baselines, astronomers would be able to create 3D maps of many galaxies beyond the Milky Way.