Texture with fading transparency

I have created a halo texture, it is 100% alpha, white in the center, and it fades to 0% alpha on the outside. The question is, how do I make it render like this when I use it as a texture on a plane?

When you go to the texture panel make sure the texture is set to affect Alpha under Diffuse but also note important Look down where it says blend and under that you have a check box for RGB to Intensity check that box.