The northern lights, or aurora borealis, are among the most spectacular sights in nature. Their southern twin, the aurora australis, lights up skies near the South Pole. Both are produced by the same chain of events that begins 150 million kilometres away, on the surface of the Sun.
This guide explains the science step by step, why the aurora glows in different colours, and how to plan a trip to see it.
The science, step by step
- The Sun constantly streams out charged particles — the “solar wind” — and hurls out bigger bursts during solar storms.
- When these particles reach Earth, our planet’s magnetic field deflects most of them, but funnels some toward the magnetic poles.
- There, the particles slam into atoms and molecules of oxygen and nitrogen high in the atmosphere, between about 100 and 300 km up.
- The collisions “excite” those gas atoms; as they settle back down, they release the extra energy as light — the glowing aurora.
Why the aurora has different colours
The colour depends on which gas is struck and how high up. Oxygen produces the most common colour — a vivid green — at altitudes around 100–150 km, and a rarer deep red much higher up. Nitrogen adds blues and purples, often along the lower fringes of the curtains. The exact mix of colours changes with the strength of the solar activity.
Where and when to see the northern lights
Auroras appear in a ring called the “auroral oval” centred on the magnetic pole. The best viewing is inside or just below this ring, roughly 65–72 degrees of latitude.
- Top destinations: northern Norway, Iceland, Finnish Lapland, Sweden, Alaska, northern Canada and Greenland.
- Best season: roughly September to March, when nights are long and dark.
- Best conditions: a clear, dark sky far from city lights, ideally during heightened solar activity.
- Southern hemisphere: the aurora australis is best seen from Tasmania, southern New Zealand and Antarctica.
Frequently asked questions
What causes the northern lights?
The northern lights are caused by charged particles from the Sun colliding with oxygen and nitrogen atoms high in Earth’s atmosphere. Earth’s magnetic field funnels the particles toward the poles, and the energised gas atoms release that energy as glowing light.
Why are the northern lights green?
Green is produced by oxygen atoms at altitudes of about 100 to 150 km — the most common and visible aurora colour. Oxygen higher up can glow red, while nitrogen adds blue and purple hues.
Where is the best place to see the aurora?
The best places are inside the auroral oval at high latitudes: northern Norway, Iceland, Finnish Lapland, Sweden, Alaska, northern Canada and Greenland. A dark, clear sky away from city lights is essential.
What is the difference between the aurora borealis and aurora australis?
They are the same phenomenon at opposite ends of the Earth. The aurora borealis occurs near the North Pole, and the aurora australis occurs near the South Pole, best seen from Tasmania, southern New Zealand and Antarctica.