I do not have much experience with digital art, so I will do the best I can.
The depth and motion you have provided for this piece are wonderful. The blurring of the closer asteroids adds very much to the picture. I like the way you created the dust near the focal point. I also enjoy the way it curls back around the planet. I feel you did a good job with the light and shading for the most part, but unless there is a light source I am missing I do not think the light should extend so far back on the planet.
A very interesting and visually appealing piece. Thank you for sharing.