How to make planets in Photoshop

I found a bunch of really awesome tutorials on how to make planets in Photoshop. I think some of these can be applied in Gimp too, and I will try some of them later, probably posting some of the results here.
The problem with Gimp is that it doesn't have an advanced layer blending options like Photoshop does. For example, you have to rely on a filters to apply shadows, which is destructive editing. In photoshop, you can adjust or turn off the shadow anytime!
Most of the tutorials use a texture, but I've seen some that make use of the filters to generate a planet-looking surface.

Here's the first one. It should be enough to guide you, it's universal and with some creativity you can extend the notions learned to create even more awesome images ( right-click and then select "View Image" to view it fullsize):

This tutorial was created by Dinyctis, on deviantArt.

Another tutorial by the same author is about making planetary rings to spice up your planets.

This is a video tutorial on the same subject, yet this time the outcome looks like a space movie poster:

Make a realistic Star Field! Although, I doubt they looks like this in reality... you can check Hubble Ultra Deep Field for a comparison :).

Create a meteor impact with a planet.




And finally, create an absolutely goergeous looking SuperNova:

Tutorial link.

These should be enough to make a you a space artist! Happy editing ;).