The sun star

You can turn the sun, or any point source of light, into a star by using a small lens aperture.  I use f/16 or smaller to get the effect you see above. In addition, a wide angle lens makes the star more defined. When I shot these chunks of ice on a black sand beach in iceland, I used a tripod, a 14mm ultra wide angle lens, and f/22.

Another way to turn the sun into a star is compose the picture such that the sun is peaking from a foreground subject.  In this case, I used the edge of the ice.  In other types of shots the foreground subject could be a tree branch, a leaf, or the edge of a building.