Heavy Airglow and Blue Water

Airglow is a faint emission of light by a planetary atmosphere. In the case of Earth’s atmosphere, this optical phenomenon causes the night sky never to be completely dark, even after the effects of starlight and diffused sunlight from the far side are removed. This phenomenon originates with self-illuminated gases and has no relationship with Earth’s magnetism or sunspot activity, causing aurorae.

The open cluster M45 Pleiades easily visible in the sky. The cluster is dominated by hot blue luminous stars that have formed within the last 100 million years. Reflection nebulae around the brightest stars were once thought to be leftover material from their formation, but are now considered likely to be an unrelated dust cloud in the interstellar medium through which the stars are currently passing.

On the ground fluorescence lichens and water using UV light. Lichens glow under UV light because they contain natural fluorescent compounds, called secondary metabolites (like xanthones and acids), that absorb invisible ultraviolet radiation and re-emit it as visible light.