Cape Town - Radio astronomers associated with the huge Square Kilometre Array (SKA) telescope project are purring after the publication of the first scientific results from the relatively tiny KAT-7 pathfinder instrument.
Last week, an international team who were among the first to test the KAT-7 telescope with its seven receiving dishes published some of their early findings in the prestigious Monthly Notices of the Royal Astronomical Society.
They used KAT-7 and the 26m radio telescope at Hartebeesthoek Radio Astronomy Observatory to observe a neutron star system known as Circinus X-1, and recorded giant outbursts as it fired energetic matter from its core into the surrounding system in brightly flaring “jets”.
Details of these jets are visible only in radio waves.
KAT-7, built at the main SKA site at Carnarvon in the Great Karoo, was designed primarily to test engineering and observing systems that will be incorporated into the much larger, 64-dish MeerKAT radio telescope under construction there.
MeerKAT, due to be completed in 2016, is in turn a precursor for the main 3 000-dish SKA, which is expected to be fully operational in 2024.
Astronomers are delighted that KAT-7 is delivering good systems and good science.
Between December 13, 2011, and January 16 last year, a team that included astronomers from UCT and the University of Southampton in Britain used the instrument to observe Circinus X-1. This is an x-ray binary (or two-star system) where one of the companion stars is a high-density, compact neutron star – a dense and compact remnant of an exploded star and only 20km in diameter.
The two stars in the system orbit each other every 16.5 days in an elliptical pattern, and when they are at their closest the gravity of the dense neutron star pulls material from the companion star. A powerful jet of material then blasts out from the system.
During their observations, the system flared twice at levels among the highest observed in recent years.
KAT-7 was able to catch these flares and follow them as they progressed – the first time the system has been observed in such detail during the full flare cycle.
Dr Richard Armstrong, an SKA SA Fellow at UCT and lead author of the paper, said these types of observation were “crucial for understanding the processes of both accretion of matter on to extremely dense systems, such as neutron stars and black holes both of about the sun’s mass, and also the so-called supermassive variety we now know to be at the centre of most galaxies”.
Professor Rob Fender, head of the Astronomy Research Group at the University of Southampton and co-leader of the MeerKAT project, said: “This project will test the extremes of physics, density, temperature, pressure, velocity, gravitational and magnetic fields”. - Cape Argus