Ring Nebula

M57 – the Ring Nebula - is in the surprising family of "planetary nebulae": this name refers to the shape of these celestial objects which in fact have nothing to do with any planet. It is a bright ring of gas ejected by a star (very dim, at the centre) at the end of combustion.

The gas composing the ring reacts in various ways to the light from the central star giving it its wide range of colours. Unfortunately these colours are invisible to the naked eye but can be seen in images such as the one below by "Chamois" (the person's pseudonym on the Futura-Sciences astro forum), produced using a CCD camera behind a 150 mm telescope with a 10 minute exposure.