You have some confusing elements to the composition of your scene.
Is the viewer positioned above watching the ship below? If so, then the planet is presumably below the ship and it is flying over?
With no light source behind or below the planet it wouldn't show much of a radiant haze for the atmosphere. Unless the planet itself is glowing.
Any light you see in space (anywhere actually) is reflecting off of something. Even when it is passing through, the color you see is hitting particles and bouncing off heading in your direction. Most of these pieces that show planets with a haze around them, are showing the atmosphere of the planet. It is reflecting light from a nearby star usually. How bright it is and how large the haze is depend on both the angle of the light's approach and the general size of the planet.
You have to think about how "high" the atmosphere is on a planet like this for you to nail down a sense of how thick that haze should be.
It wouldn't all be a perfect spherical bubble around the planet either. You would be better to try to capture a feeling of fog perhaps.
Brightest at the edge of the planet where that atmosphere would be the thickest (more to bounce off of) and fading out gradually.
Suggestion, shrink the size of your gradient bands, they feel huge.
Try to bring your contrast down some between each color.
Try not to be so perfectly circular on the gradient boundaries. Those long straight lines stand out to the human eye really heavily.
