An artistic illustration of a black hole or solar eclipse, I guess.
Forget making it in Illustrator. If the small grains were vectors the work would have say 80000 paths and 400000 anchor points. Such mass would make everything slow like swimming in tar. A little less heavy way would be to use noisy glow effects, but they are finally raster images. As well you could use Photoshop or some other raster image painting program.
Photoshop would make it all easier because there you could use paint brushes to get some nice strokes (assuming your eyes, hands and the grey matter between your ears are up to the task).
The metallic like ring is especially trivial in Photoshop. It's a ring filled with a vertical gradient and the edge glow is Bevel&Emboss layer style. But the grainy cloud is tricky. It may use layer blending mode Dissolve to make the grain, Or it may be painted by having the brush in Dissolve mode. Or the grain is generated by using glow layer styles with noise. Impossible to say. But replicating it exactly from scratch succeeds only if one is a skilled painter in digital media. I'm not one, so I drew only a couple of random strokes. The grain is by Dissolve. It transfers partial transparency to grain.
Note that in the original there's also a shadow painted below the ring. The dots which resemble stars in astronomical photos are only dots. I skipped them, too.