TOPIC OF THE MONTH – COSMIC RAYS

COSMIC rays are high-speed particles – the nuclei of elements travelling at almost the speed of light – and most astronomers believe they originate from supernovas (star explosions).

Cosmic rays constantly rain down towards Earth from space and roughly 90 per cent are hydrogen nuclei (protons), nine per cent are helium nuclei (alpha particles) and the remaining one per cent are the nuclei from other elements. Cosmic rays can be dangerous to humans, but on the surface of the Earth we are protected from them by the Earth’s atmosphere, which stops all but the highest energy cosmic rays, and by the Earth’s magnetic field, which deflects cosmic rays towards the polar regions.

Some cosmic radiation is present at the high altitudes airplane fly at, and for that reason female airline personnel who are pregnant are advised to fly lowlatitude routes and to avoid flying polar routes.

However, in space, without the Earth’s protection, cosmic rays can have a more serious effect on astronauts, increasing the risk of various illnesses from cataracts to cancer.

These risks will be a big problem as humans travel longer in space and as we make bases on the Moon and on other planets which don’t have an atmosphere to protect them.

NASA is giving a lot of thought to the design of space crafts and bases, perhaps storing water in the outer shell of these habitats to shield astronauts the impact of cosmic rays.