Once again, a space-piece that has the specific *bloknayrb-fingerprint. It's hard to actually describe it, but one can easily recognize your style. Maybe it is caused by the black and white color scheme which has been prominent in many of your pieces. I don't want to say that it's bad, I just want to encourage you to look for good color-combinations from time to time. Even if it's just monochromatic, it does make a difference in many cases.

Compositionally, there is absolutely nothing to complain about. The light source is nicely countered by the small planet in front of a very faint nebula that does not steal the focus.

In terms of details, there is still room left for improvements. For example, the gas giant on the right seems a bit artificial. Gas planets that have some sort of weather generally tend to have swirly areas rather than wave-like shapes. Try to study a bit of hydrodynamics; not directly what causes what but how it looks like. It does have some useful aspects in that matter. In doubt, you can always use Jupiter-images as references to see how the gases swirl around
As for the smaller planet, the details are a little too subtle. Even at full size, the crack is hard to make out, and the texture is barely visible. As it represents, compositionally, a point of interest, it would be great if you could the eye some food, so to say.

The starfield itself is nice -- bigger as well as smaller stars are nicely depicted. The only improvement-idea that comes to my mind would be the creation of clusters. Also, a closer interaction with the nebula could come in handy (ie. darker gas clouds obscuring the starlight or lighter areas simulating cradles of new stars). Some extremely faint nebula-like shapes scattered around would probably help blending the current nebula a bit more so that it doesn't look so isolated.

The main light source looks a bit simple for my tastes (so it's fully up to you and how you see it; I just want to mention it for completeness's sake). The fade-out seems slightly unnatural going from a fairly solid mid-gray to invisible pretty quickly. Now, my preferred way would be to create a lens-flare-effect (oh no, I used the evil word). Not like "Filter > Render > Lens Flare" but like "Brush, Brush, Brush". It's certainly a bit harder but the result will be much more satisfying

Overall, a really nice piece. Yes, some flaws are here and there but the general idea is great. The asteroid-belt is looking cool; it really creates the illusion of looking at rings of dust. The wide aspect ratio definitely supports the composition which, again, is splendid. Great work, keep it up!