Realistic space environments You've seen it in all kinds of science fiction, be it books, games, movies, and such. Space is depicted all sorts of ways, with asteroids far too close together, nebula thick enough to hide in and much more. Yet for a writer that want's to describe space accurately, this is a problem. 

So I need stellar features and reasons why they would form/exist

Here's a rough list of what I'm talking about:


Thick asteroid style fields, averaging around 100 meters apart
Nebula regions that are actually thick enough to obscure light, like clouds
Dust cloud regions thick enough to obscure light
Any other kind of cloud of material that's similar to the two above
Naturally occurring fields of explosive gas or a physical material that does the same
Radiation levels high enough to eat through ship plating
Naturally occurring anomalies of any sort, such as black holes, rogue planets and stars


An example would be a protoplanetary disc. Could this allow for material in close proximity so you have rocks in orbit that are close together? What about clouds of material? Would a forming star would have a thick cloud of material around it?

Anything naturally occurring or even unnaturally occurring is fine, so long as space magic or whatever isn't involved.

If I missed anything you can think of, please elaborate. This topic has been difficult for me to find information on.

Extra question: Could a cloud or clouds of opaque gas exist, even for a short time in space? With or without other material present works.
Thick asteroid style fields, averaging around 100 meters apart


That's a very high density. It's not any "asteroid" field that would occur naturally and would be stable for a long time. I can only think of a few environments that would be close to that:


the ring around a big planet, like Saturn
the debris field shortly after a major planetary collision, like the one that created the Moon. It would be a very dangerous place to be in, because not all fragments would move at the same speed; there would be quite an ongoing amount of collisions.
maybe, and this is a very cautious maybe, the pile of material coalescing into a protoplanet


All of the above would be short-lived, on a cosmic scale. It would be a coincidence that you're there to see it, and you'd probably have to explain the coincidence somehow.

"Asteroid fields", the way most people imagine them nowadays (very high density), are largely fiction, originating in the iconic space chase sequences in the Star Wars movies, and the like.


  Nebula regions that are actually thick enough to obscure light, like
  clouds


On what scale? Quite a few nebulae obscure light, but we're talking on the scale of distance between two neighboring stars. There are some nebulae that glow from within but we don't quite see the star - that's an example.

If you're talking about blocking light on the scale of mere kilometers, that's not possible "in outer space". Not for nebulae, not for dust clouds or anything else. That would be a density approaching the atmosphere of a planet. Consider the Earth - you can see just fine kilometers away through its atmosphere, unless fog gets in the way.


  Naturally occurring fields of explosive gas or a physical material
  that does the same


Even if you could find something like that, which is pretty much impossible, it would be highly unstable, and would eventually decay into the lower energy state - i.e. it would tend to explode. Such things might exist for the duration of a cosmic blink of an eye. It would be quite a coincidence that you could find something like that out there. A coincidence that would require some explanation, and very likely would not be a "mere coincidence". I think that's called a plot point. ;)

Such things just don't occur naturally.


  Radiation levels high enough to eat through ship plating


It would melt off, rather than being eaten through. Radiation tends to be absorbed; it doesn't tend to chip material away. And when it's absorbed, it yields its energy as heat.

Also, there is no material that could shield nuclear radiation so well that it would melt off on one side, while blocking it to non-lethal levels on the other side. At least not within any reasonable thickness.

Anyway, such conditions might be found near extreme places such as the polar jets of massive black holes - but only while the accretion disk is very active.

https://en.wikipedia.org/wiki/Astrophysical_jet


  Naturally occurring anomalies of any sort, such as black holes, rogue
  planets and stars


Black holes are pretty ordinary, not anomalous in any way. There are huge black holes in the center of galaxies, and regular-size blackholes sprinkled throughout.

Not sure what you mean by "rogue planets and stars". Planets not belonging to any star system are actually thought to be pretty common. Stars not belonging to any galaxy are also not extraordinary, but of course the distances between them would be gigantic, since any such star, by definition, would be alone in intergalactic space.


  An example would be a protoplanetary disc. Could this allow for
  material in close proximity so you have rocks in orbit that are close
  together? What about clouds of material?


Yes and yes. But at that point it would evolve rapidly, coalescing into a planet. Not rapidly on the human scale, but rapidly on cosmic scale. To you, as a human being, it would seem quite stable.


  Would a forming star would have a thick cloud of material around it?


The transition between a disperse, rarefied cloud of gas, and an actively burning star with a clearly defined "surface" is very rapid. However, for a very brief time (maybe thousands of years? not sure), you might find something with a dense center, surrounded by a thin cloud; but even then, density near the central area would increase rapidly. Perhaps you need to ask an actual expert in stellar evolution; there are models that show exactly how each phase looks like and how long it would last.

If you're looking for large expanses of gas or dust at densities comparable to Earth atmosphere, such a thing is simply not stable on a cosmic scale. It either dissipates if there's not enough gravity to hold it together, or it's part of an active process of collapse as a protostar or protoplanet.