ASTRONOMERS working on the KAT-7 radio telescope have published their first scientific paper, a milestone that is as much about proving the device is up to scratch as it is about doing cutting-edge science.

The KAT-7 is a critical precursor to the much bigger MeerKAT, which in turn is a pathfinder for the Square Kilometre Array (SKA), which will be the worlds most powerful radio telescope when completed. South Africa is co-hosting the SKA with Australia and has invested heavily in the project, with R2bn set aside for it over the next three years alone.

South African and foreign scientists have used the KAT-7 and the radio telescope at the Hartebeesthoek Radio Astronomy Observatory to observe periodic jet flares emerging from a binary star system called Circinus X-1.

This star system consists of a neutron star and an ordinary star that orbit each other every 16.5 days in an elliptical orbit.

When these two bodies are at their closest, the gravity of the dense neutron star sucks in matter in a plate-like disc from the ordinary star and fires it out again in a powerful jet, which can be detected with a radio telescope, said Richard Armstrong, SKA SA fellow at the University of Cape Town and co-author of the paper, published on Thursday in the Monthly Notices of the Royal Astronomy Society.

"With KAT-7 we were able to see details of two extreme radio flares, and show that the power of these jets may be connected to a decrease in the accretion rate of the neutron star," he said.

Accretion describes the way a neutron star "gobbles" material from the other. It is the first time Circinus X-1 has been observed in such detail over several flare cycles. While it is clearly important to astronomers working in this field, it also has bearing on the overall SKA project.

"KAT-7 was really intended as an engineering test bed to refine the design and systems for the MeerKAT telescope that we are working on now, but we are absolutely delighted that it has turned out to be a top quality science instrument, capable of producing significant science," said Rhodes Universitys Prof Justin Jonas, associate director for science and engineering at the SKA project office in South Africa.

Science and Technology Minister Derek Hanekom said the publication proved South Africas engineers could deliver a cutting-edge scientific instrument capable of conducting "frontier" science.

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Radio astronomy publication a milestone for SA