How can I this kind of effect around the stars ?
Which effect are you taking about - the surface granulation, the prominences or the glow?
Stuff like glows is better done with compositing. Just using the glare node would be a basic example of this. Using the new filmic colorspace also helps when driving high-intensity light sources, because it deals with clipping. (In terms of image brightness.) The test versions of Blender have filmic, and I haven’t had too many problems with stability.
Now the stuff like the actual flares on those stars might be neat to try with volumetric (emitter?) materials. That’s something I’d be curious if anyone else has tried figuring out.
both effects but maybe the prominences is more very interesting
yes the compositor or simply download this than shift+F1 to append the world and apply it in your scene
http://www.markkingsnorth.com/category/nebulas/