South Africa must not forget or neglect smaller-scale astronomical and astro-physical experiments because of the attrac-tion created by mega-experiments like the international Square Kilometre Array (SKA) radio telescope project, warned North-West University emeritus physics professor Harm Moraal. A good example of such smaller-scale programmes is South Africa’s network of neutron monitors.

South Africa has neutron monitors at Her-manus, Potchefstroom and at the country’s Sanae Antarctic base. In addition, Namibia has such a monitor at Tsumeb, which supplies data free to South African researchers. Neutron monitors are used to indirectly record cosmic ray activity. The Hermanus monitor, the country’s oldest, has been doing this since June 1957. It is, in fact, the longest continuously operating neutron monitor in the world.

“Regarding cosmic rays, the value of the record lies in its continuity,” he noted. “A minimum global network is required. South Africa should upgrade its neutron monitors.”
South Africa’s neutron monitors have been designed and assembled locally by electronic engineers and would also be upgraded locally. Indeed, ten years ago, North-West University started a project to develop, make and sell mini neutron monitors. The first example was sold three years ago and, since then, a total of five such units have been sold to research agencies in Germany, France, Italy and Mexico.

Neutron monitors detect neutrons created when cosmic rays hit the earth’s atmosphere. Cosmic rays themselves very rarely reach the surface, the atmosphere pretty much acting as a barrier to keep them out. Their name is a misnomer as they are actually very high energy charged particles – 90% of them are protons, 5% are helium nuclei and the rest are made up of heavier nuclei and electrons. Because they are charged, because the galaxy is full of magnetic fields and because they follow the magnetic field lines, cosmic rays come from all directions of the sky equally.

But they can still provide important infor-mation. Firstly, their sheer speed – effectively, the speed of light in a vacuum – reveals that tremen- dous acceleration forces exist in the galaxy. These are most probably shock waves created by supernova explosions. Secondly, the particles which make up the cosmic rays tell us about the composition of the interstellar medium within our galaxy.

Moraal described the study of cosmic rays as particle astronomy, as distinct from “photon astronomy”, which is concerned with the electromagnetic spectrum (including visible light, radio waves and X-rays). Particle astronomy also includes the observation of very-difficult-to-detect particles called neutrinos, but, to be effective, a neutrino detector has to be huge and, consequently, was very expensive. The biggest and best neutrino detector in the world, the American IceCube, located at the South Pole, is 1 km in size. Cosmic ray studies through neutron monitoring are, however, well within South Africa’s financial capabilities.

He pointed out that South Africa was commit-ted to multiwavelength astronomy, borne out by the range of observatories already operating (the South African Astronomical Observatory and the Southern African Large Telescope, in the optical wavelengths; the Hartebeesthoek Radio Astronomy Observatory; and the KAT-7 array, in the radio wavelengths) and planned (the MeerKAT radio telescope array and the SKA). Further, there was now a draft ten-year strategy for multiwavelength astronomy in the country. Consequently, he urged that particle astronomy be included in this multifaceted approach.

Moraal presented a paper during a plenary session of the 2014 South African Institute of Physics conference at the University of Johan-nesburg. Talking to Engineering News, he stressed that the threat of neglect of smaller experiments applied in all the natural sciences in South Africa.