M 10 (NGC 6254) is a globular cluster 14,300 light
years away in the constellation Ophiuchus. It is
83 light years in diameter. Stars like our sun
create heat and light by converting hydrogen into
helium through nuclear fusion. The orange-red stars
in this cluster have used up most of their hydrogen, and
have expanded into "red giants". The blue stars in the
cluster have moved on to an even more advanced stage of
life, and having used up their hydrogen are fusing helium
into carbon. They will soon shed their outer layers, and
become "white dwarf" stars. Be sure to look at the "original"
size to see these red and blue stars clearly.

Image data:
Camera: Canon 350XT (modified)
Exposure: ISO 800, 1 minute x 30
Telescope: 10" Schmidt-Newtonian, Baader coma corrector
This image has been cropped.