M 17 is an emission nebula. Some of the huge hydrogen cloud
has been caused to glow by a cluster of stars embedded in and
hidden by the nebula. Darker areas of gas and dust obscure part
of this lit-up cloud, giving the nebula its distinct shape. It
is sometimes called the "horseshoe", or "omega", or "lobster" nebula;
but it is most commonly known as the "swan nebula". It is about 6800
light years away, in the same general area as M 16. There is enough
material in M 17 to make 800 suns.

Image data:
Camera: Olympus OM-1
Film: Ektachrome 1600
Exposure: 6 minutes
Telescope: 10" Schmidt-Newtonian