Astronomy Picture of the Day

Explanation: What a sight to behold, when a night sky became filled with colours that appeared to rain over the Skógafoss waterfall in Iceland. This image was taken in a single 5 second exposure by the photographer in April 2025. Seeing an aurora is on many people's bucket lists. But it is not easy. It requires high solar activity, dark and clear skies, and usually a viewing location at high latitude. That makes the northern lights more easily seen than the corresponding southern lights, simply because there is less landmass in the Southern Hemisphere, especially around the Antarctic Circle. Aurorae are caused by charged particles from the solar wind that are captured by the Earth's magnetosphere and guided by the magnetic field to a region close to one of the poles, where they collide with gas particles in the atmosphere. Different colours indicate interactions with different gases at different altitudes, like oxygen (red and green) and nitrogen (blue and pink).