can anyone point me to an article or tutorial on rendering an atmosphere around a sphere?
thanks
You can do simple atmosphere by rendering a blended blue sphere with a larger radius over you earth.
very simple but not very realistic 
Look for the “Earth” demo at http://sourceforge.net/project/showfiles.php?group_id=29749
Source (in Delphi) can be found at http://cvs.sourceforge.net/viewcvs.py/glscene/AdvDemos/Earth/
It uses some basic raycasting calculations, which are then used as vertex colors for an atmosphere mesh in real-time (an overlay actually). The raycasting and OpenGL rendering code is in the TForm1.GLDirectOpenGL1Render of Unit1.pas.
thank you guys