First place in the 2021 IAU OAE Astrophotography Contest, category Aurorae (still images) Aurorae are the result of ionisation and excitation processes in Earth's upper atmosphere, caused by charged particles from the solar wind or from coronal mass ejections. The different colours in an aurora display indicate the species of atmospheric atoms and molecules involved. The most common colour is a bright green, which, together with deep red, originates from atomic oxygen. Blue, purple and pink hues are much rarer and originate from molecular nitrogen. The reflection of the aurora in the water indicates the brightness of intense aurorae at higher latitudes. Credit: Marco Migliardi on behalf of Associazione Astronomica Cortina/IAU OAE.