The northern lights, with their vibrant displays of green, pink, and violet hues, have become a famous attraction in Nordic countries. But in early October, a rare sighting of the southern lights – or aurora australis – was reported in South Africa, surprising many.
Prof Pieter Meintjes, Professor in the Department of Physics at the University of the Free State (UFS), explains that both the northern and southern lights are the result of charged particles from coronal mass ejections (CMEs) on the sun, which are captured by Earth’s magnetic field. "The interaction between magnetic fields and charged particles, such as protons and electrons, is very interesting. The magnetic field forces these particles to spiral around the field lines, ultimately guiding them towards the magnetic poles. As these particles enter Earth’s atmosphere, they collide with atmospheric atoms, causing a beautiful glow. The colours of the aurora indicate which atoms are involved. Typically, hydrogen shines red, while oxygen and nitrogen produce a greenish-blue tinge," he says.
Observing the southern lights
When the display occurs above the northern magnetic pole, it is called the aurora borealis (northern lights) and can typically be observed over regions such as Alaska, Greenland, and the Nordic countries. Above the southern magnetic pole, it is known as aurora australis (southern lights), usually visible over places such as Antarctica and New Zealand. “In extreme cases – when gigantic mass ejections occurred – it can also be observed in mid-latitudes such as South Africa,” says Prof Meintjes.
This recent and rare South African sighting was also captured by the BOOTES-6 telescope station at Boyden Observatory, located just outside Bloemfontein. According to Prof Meintjes, the telescope station has an all-sky monitor – a camera constantly watching the sky for changes and monitoring, among others, cloud cover to ensure that the telescope is always safe from weather. While the monitor was taking photos of the night sky, Prof Alberto Castro-Tirado, a research professor at the Institute of Astrophysics of Andalusia in Spain, picked up the aurora.
The Institute of Astrophysics of Andalusia in Spain, in collaboration with the University College Dublin (UCD), is partnering with the UFS in a research-driven initiative involving the BOOTES-6 telescope station, installed in 2022 during the COVID-19 pandemic. Under a Memorandum of Understanding that was recently renewed for another five years, the UFS and UCD share approximately 30% of the telescope's observing time dedicated to UFS research.
“The DPRT telescope (Dolores Pérez-Ramírez telescope), named after a Spanish astronomer and lecturer at the University of Jaén, contributes significantly to our research, with publications resulting from contributions made by the telescope station and collaborators on gamma-ray bursts, occultations, and transient events co-authored by me and a colleague in the department, Dr Hendrik van Heerden,” notes Prof Meintjes.
Research-driven initiatives
Data from the telescope station is also used for their in-house projects and contributes significantly to the work of their PhD students that will be submitted in the next few years. This includes the PhD work of Helene Szegedi, who uses data from the BOOTES-6 telescope station to study cataclysmic variable systems – compact binaries that erupt regularly. Another PhD student, Joleen Barnard, studies blazar variability under the guidance of Prof Brian van Soelen. Blazars, explains Prof Meintjes, are the core of distant galaxies powered by supermassive black holes. These cosmic jets are pointed towards Earth, but fortunately, they are millions or billions of light years away; otherwise, their impact would be devastating to life on Earth.