What is a Nebula?

Crab Nebula
Crab Nebula

The Birth of a Star

This phenomenon is the result of gravity pulling gas and dust together. It is a process that is multiplied millions of times within the nebula and the beautiful objects that are forming are the fetal stages of stars being created.

Specifically, the gas is a combination of hydrogen and helium which clump together to form larger masses and since gravity gets stronger as the mass of the object gets bigger, additional matter is attracted to the object, which eventually becomes massive enough to form a star. In other words, it is the gravitational force of an object that is directly proportional to the object’s mass.

Nebula’s Molecular Breakdown

Veil Nebula
Veil Nebula

Unbeknownst to many, most of the universe is not a complete void. There is much (loose) matter floating around between the stars. And this matter is not visible to the naked eye, as it is in its atomic form; such as, the atoms of hydrogen and helium, as well as plasma and other materials. This sub-atomic matter is called the interstellar medium (ISM). More specifically, the interstellar medium is composed primarily by hydrogen, followed by helium with trace amounts of carbon, oxygen, and nitrogen.

In areas of the ISM where the atomic particles are densely populated, the formation of molecules begins, most commonly hydrogen (H2). The more the molecular masses clump together, the greater their gravitational attraction will be to other bodies and particles in their vicinity. As the particles clump further to form larger and more massive structures, they attract more dust and gas.

The Nuclear Element

Enter nuclear fusion, since the gravitational pressure becomes so high that the fusion of hydrogen atoms occurs. This results in the emission of high-energy electromagnetic radiation, which in turn ionizes the outer layers of gas. Ionization is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons to form ions.

Ionized gas is known as plasma, and plasma along with electromagnetic radiation are now added to this mixture. This then materializes into the early stages of star formation.

Hence, the formation of stars occurs exclusively within these molecular clouds. This is a natural result of their low temperatures and high densities because the gravitational force acting to collapse the cloud must surpass the forces that are working to push the particles outward and the molecular cloud is now a nebula.