Cosmic Clouds
Cosmic clouds: Clouds of gas and dust, glowing brightly by emitting many forms of radiation

Appearance is like light clouds on a partly overcast night on Earth

Most of the gas and dust originated from the death of stars which either exploded (supernova) or blew off their outer layers.

Both the gas between the clouds and the clouds themselves are mainly composed of hydrogen and helium.
But there are small amounts of other elements, such as carbon, oxygen, and nitrogen.

There are occasional stars within the clouds.

These stars play an important role, providing much of the radiant energy that drives physical and chemical processes within the cloud.

Atoms and molecules exist within the clouds in space between the dust grains, but their density is much less than what’s expected with Earths standards, (atoms and molecules can be km’s apart from their neighbours) – however, this density is still a million times greater than that of the matter in the space between galaxies.
The density varies greatly from place to place in the clouds.

Gravity usually forces them to contract to higher and higher densities, heating up as they contract until they begin to emit radiation because of their high temperatures. It is this radiation that illuminates the cloud, rather than the feeble light emitted by the clouds themselves.

With the densities of atoms in most places in the gas clouds (being very sparse), collisions are very infrequent.

It is possible that the interstellar molecules are formed on the dust grains. Atoms may collide with the grains and stick to them. If many atoms are on the same grain at once, they have a much greater chance of forming a molecule than if the same atoms collide in space.

In our Solar System, the interplanetary dust particles have a role in scattering sunlight and in emitting thermal radiation.

‘Life Beyond Earth,’ also suggests that the clouds may furnish a possible biosphere and be the basis for the existence of a totally different form of life—radiant life.

p. 393 – Radiant Life in (Almost) Empty space
2 example clouds:
1) Chaotica, is a typical cloud of average density, remote from the centre of the galaxy, and whose properties are very similar to the clouds described above.
2) Radia, is denser and closer to the galactic centre. Most notably, it has been transformed by the presence of a life form—radiant life.

While the atoms in the cloud do not interact easily through collisions, they can influence one another by exchanging radiation.

Radiation of various types is emitted by nearby stars and absorbed by the atoms and molecules in the cloud. Different atoms and molecules emit and absorb specific wavelengths. Particular wavelengths would only be influencing certain molecules in the cosmic cloud.