Attached Link: The Ultimate Gimp Planet Tutorial

A couple more suggestions.  First, turn down the reflection on the planet surface and the glow layer.  Unless there is water, planets don't normally reflect.  Also reduce the Highlight for the same reasons..  Depending on the map file you are using for the texture, it can be a bit difficult to get right since flat maps images tend to pinch up near the poles when placed on a surface.  I usually use GIMP or PSP to develop a planet.  There is a great basic tutorial here...

http://www.tutorialized.com/view/tutorial/The-Ultimate-Gimp-Planet-Tutorial/40845

Then I create the background around that image.  It's easier and I think it comes out better.  I make the backdrop as high a resolution as I can depending on what surface map I used for the planet.  Look at my gallery for some examples in some of my newer uploads.

If I have to do it in Carrara, I use 3 maps and three or 4 spheres.  The first sphere is for any water or ocean.  The second sphere is fr the land masses.  For the land masses, I make the sphere about .08 inches larger os it just barely blocks out the firt sphere.  I modify the landmass texture map so there are pure white spots on it where I want he water to show through.  Then on the landmass sphere, check White is Invisible, and add a Mixer shader to the bump channel of the landmass sphere.  In the Mixer, sure the bitmap that you used for the landmass for the first source. Next, put in a value of 1-1000 for he second source and select a Multiply for the method.  Next create a third layer just a tiny bit bigger again for the clouds.  Select or create a cloud bitmap, and then another for the halo which is just a plain color at about 98% transparency and with a subtle glow. Some folks choose to use an Aura under the spheres effects tab, but then you get shadow issues.  I usually do not use a distant light.  Mostly because natural sunlight doesn't behave like that.  I either use a sun light and place the actual source where the sun is, or I use a spot.  Play around to see what looks best for your particular scene. 

Oh yeh..  Almost  forgot.  If you decide to go the easy way and do the backdrop in a 2D app.  See about picking up Alien Skin's Xenofex II.  It has a plugin called constellation which is great for making starfields.  Just make a series of layers with starfields and then change their colors brightnesses etc...  Add in a few nebula layers and it looks fantastic.  Xenofex is a plug in for Photoshop or Paint Shop Pro (my favorite).

Pertaining to your render  I would also move the camera farther off to the side and make it much higher than the planet on the Z axis.  Reduce the bump a tiny bit too.

I hope this is helpful.

Rich

PS I will attach one of my images for you to look at.  The planet was done in GIMP then brought into Paint Shop Pro where I created the starfield and used the planet as the top layer.  When you design a planet this way, Make sure you are creating it on a BLACK backdrop.  BTW  If you don't have GIMP then you can get it free on the net.  It's 100% Public Domain Freeware.  Just Google GIMP.