The image is painted in Photoshop. In the beginning I did no know how to make it and I rendered an image in Terragen. This did not do it at all in so I overpainted it. :)
95% of the image are painted with brushes(the sun with the help of a "differencial clouds-filter" and a warp-filter) and 5% are remnants of Terragen which I used as textures.

The is the Terragen-Image:

Terragen-render

For the moon in the sky I used a Terragen-Texture es well.

What you see here is a planet surrounding an active M-Star(cooler than the sun) in a close orbit. At least as far as I imagine it to look like :)
Because of the heat of the sun the surface melts and gets solid again.