What is that strange light in the night sky?

The Central West of NSW and other parts of Australia have been graced by colourful natural night-time light shows in the past few years. These light shows, known as the Aurora Australis or Southern Lights, are usually only seen in Antarctica and southern Australia. Another such event occurred last week. You may be wondering what causes these amazing light shows in the night sky. We know that our Sun gives off huge amounts of light and heat. However, the Sun also gives off massive amounts of other energy such as Gamma, X-ray and Ultraviolet radiation, as well as Radio energy. This energy is known collectively as electromagnetic radiation, or electromagnetic energy, or simply “light”. This beautiful image of the recent Aurora Australia was taken by CWAS member Alison Ferguson on 20 January, 2026 near Hay, NSW. (Note the green colour, which is very rarely seen this far from the South Pole.) Strangely enough, although these various types of energy appear to be quite different to each other, they are actually the same “stuff” and only differ according to their wavelength. For example, they all travel through space at the so-called speed of light, approximately 300,000 kilometres per SECOND! (This is why an optical telescope that studies visible light looks different to a radio telescope such as the Parkes Dish, even though they actually operate in a surprisingly similar way.) The way this electromagnetic energy or light travels through space from our Sun and other stars is similar to the way waves move through water at the beach. The waves have a so-called wavelength, which is the distance between one wave crest and the next crest. The really dangerous Gamma, X-ray and Ultraviolet energy have tiny wavelengths that are the size of atoms. The much safer Visible light and Infrared (heat) energy have wavelengths that are relatively much longer but still a fraction of the thickness of a human hair. Radio energy has even longer wavelengths, in some cases centimetres or even many metres long. The reason why Gamma, X-ray and Ultraviolet energy is so dangerous is that their far shorter wavelengths result in much more energy compressed or concentrated into a beam. On the other hand, Radio energy, for example, is far less concentrated and therefore not as dangerous. Fortunately, only the safe Visible light, Infrared heat and Radio energy are able to get through to the surface of Earth. The dangerous Gamma, X-ray and Ultraviolet radiation are filtered out by our atmosphere and deflected away from us by our planet’s magnetic field; the same magnetic field that makes our compasses work. (A small amount of Ultraviolet energy does manage to reach Earth’s surface, which is why we have to protect ourselves from sunburn.) In fact, the beautiful aurora that we sometimes see in the night sky is caused by extra strong energy outbursts from our Sun of Gamma, X-ray and Ultraviolet energy clashing with our magnetic field. So the next time you see a beautiful aurora, whether above Parkes or more often in southern Tasmania, consider that it’s not just a spectacular natural light show. CWAS member Stephen Holland took this colourful image of the aurora on 20 January, 2026 at Cudal, NSW. It’s also the result of our beautiful planet Earth keeping us safe. If you would like to learn more about aurorae and other aspects of astronomy, the Central West Astronomical Society will be meeting for the first time in 2026 on Friday, 6 February, commencing at 7:30pm upstairs in the Sunset Room of the Parkes Services Club in Short Street. Attendance is free and members of the public are always welcome.