Rotating an image with null and image always facing camera?

I'm animating a ball that I made with cc sphere, meaning it's a 2D image basically. 

(to make it render faster, I animated the cc sphere out in a movie file and imported into the project)

It's basically a planet rotating (it's in the movie) that rotates around the sun

I'm spinning it around in 3D space in a horizontal circle - I'm using a null for this, since I want to the ball to get closer to the center over time.
When I rotate the null, the image also turns revealing it's a flat image.
Since I'm not animating my camera but the image - is there a way to have the image always facing front?
(I'm looking for a similar solution to  auto-orient face camera, but since I'm not animating the camera this doesn't seem to work)

Any direction would be much appreciated.

Cheers, Dan