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Astronomy Section Communique spring 2024

Astronomy Section Communique spring 2024

The northern lights, also known as the aurora borealis, are beautiful dancing ribbons of light that have captivated people for millennia. They are typically confined to high latitudes, but as solar activity has increased, they are occasionally visible as far south as Guernsey, including during the night of 10/11th May 2024.

To see a recording of the entire event captured from the David Le Conte Astronomical Observatory All Sky Camera please see:>All Sky Camera.

Figure 1 – Rousse Tower, image credit Carl Bideau

Auroras are the visible manifestation of a solar storm, associated with a coronal mass ejection, where high energy solar particles are discharged into space and head towards Earth, where they can travel down the magnetic field lines at the north and south poles into the atmosphere. When charged particles from the Sun strike atoms in Earth’s atmosphere, they “excite” the gasses, moving electrons to higher-energy orbits, further away from the nucleus. Then, when an electron moves back to a lower-energy orbit, it releases a particle of light or photon. This process goes on all the time, but during high solar activity a large number of solar particles bombard the atmosphere, when the oxygen and nitrogen can emit enough light that it is detectable by the naked eye.

The colour of the aurora depends on which gas is being excited by the solar particles, and how excited it becomes. It also depends on how fast the solar particles are moving, the faster they are, the higher the energy at the time of collision with electrons in the atmosphere. High energy electrons cause oxygen to emit green light, while low energy electrons result in red light. Nitrogen tends to give off blue light. All these colours can be blended in a display to give shades of purples, pinks, and whites. The various colours can be seen in photographs taken by Astronomy Section members.

Figure 2 – Powder Magazine Fort Le Marchant, L’Ancresse, image credit Jacques Loveridge

Aside from being beautiful and mesmerising, the aurora show eloquently how the Earth’s magnetic field protects life on our planet. Our neighbour Mars once had a global magnetic field that provided similar protection and thus, it also had oceans and an atmosphere. However, Mars lost its global magnetic field over time, this meant that the intense bombardment by solar particles gradually stripped away its atmosphere and oceans, leaving behind an inhospitable, cold and dusty planet.

Descriptions of the aurora can be found in many early cultures, where ancients thought of them as great dragons or serpents in the skies. In Scandinavia, Iceland and Greenland where the aurora borealis is common, it was seen as the great bridge Bifröst, the burning archway between and by which, the gods travelled from their realm and Midgard (Earth).

At the moment solar activity is reaching a high as the latest 11-year solar magnetic activity cycle or Schwabe cycle, peaks. More information on this can be found in the recent La Société Guernesiaise Transactions. Hopefully, there will be more opportunity this year to see the aurora borealis. For the best viewing find a dark location and look towards the north. Ideally, let your eyes adjust to the dark and you will start to see more detail. To keep informed on auroral activity and receive alerts to your phone see the website:

Figure 3 – Pembroke Bay, image credit Hugh Whitchurch

Figure 4 – Ladies Bay, image credit Alison Moullin

Figure 5 – La Jaonneuse Bay, image credit Jean Dean

Figure 6 – Fort Le Marchant, L’Ancresse, image credit Jacques Loveridge