I think you've done a great job here illustrating a "gap in space." Artistically, you've decided to depict this spatial chasm as a blinding white light instead of the typical "black hole," which I thought was really creative. The gap expands horizontally, but also appears to create shock waves vertically, adding another layer of uniqueness to this image. We can clearly see the effects of the time gap on the smaller spatial object on the right, as well as the planet on the left. You've also put a lot of detail on said planet, and the swirled texture is really cool. The red of the planet also provides just enough contrast for the image as a whole. This is definitely one of my favorites that you've done. Keep up the good work!
I understand. But the only way you will get noticed is by posting your stuff out there, regardless of whether it will be copied or not. If it is ever copied, you simply have to report it. As you would have the earliest submission, it proves that you are the original author.
There is no way to show off your art without having a risk of it being copied.
And believe me, there is no point into adding a huge watermark right through your art as it will just make it look unappealing.