Interstellar clouds can be large, up to 106 solar masses, and are often said to be the most massive entities in the galaxy. In this form, they may have a lifetime of more than 108 years. They are presumably dissipated as a result of pressure from stars formed within the clouds.
An interstellar cloud is generally an accumulation of gas, plasma, and dust in our and other galaxies. … An interstellar cloud is formed by the gas and dust particles from a red giant in its later life.
Summary: Stars form in cold, dense regions of space called molecular clouds. When the force of gravity pulling in on the cloud is greater than the strength of internal pressure pushing out, the cloud collapses into a protostar.
As our Sun and planets travel through interstellar space in our part of the Milky Way Galaxy, we exist in a region called the Orion Arm. Within the arm are clouds of gas and dust, and regions that have less than average amounts of interstellar gases.
Bottom line: Interstellar space is the space between the stars in a galaxy. It's not “empty,” but, overall, it's as close to an absolute vacuum as you can get. Molecular clouds are places in interstellar space where the material is collected most densely. Within these clouds, new stars and planets are born.
Gravitational forces caused the gas in the thin disk to fragment into clouds or clumps with masses like those of star clusters. These individual clouds then fragmented further to form stars.
500 reflection nebulae Reflection nebulae and emission nebulae are often seen together and are sometimes both referred to as diffuse nebulae. Some 500 reflection nebulae are known.
It is unlikely that such a nebula, or any astrophysical gas collapses with zero angular momentum, thus the gas is probably initially spinning at least slowly. Because of conservation of angular momentum, the cloud spins faster as it contracts.
The primary source of spin in nebulae (also for galaxies), is torque from the local environment. Nearby nebulae, clouds, stars, etc can exert a net torque on the nebula (or galaxy) giving it angular momentum. This is the primary source of spin for nebulae.