which factor is essential to the initial formation of galaxies, for either of the theories describing galaxy evolution
the force of orbiting stars generates collisions
massive gas and dust clouds collapse
small lumps of material merge into larger clumps
gravity acts on existing material, shaping it into a new form
All of the mentioned factors are important for the initial formation of galaxies according to the theories of galaxy evolution. However, if we had to choose one factor that is essential for the initial formation of galaxies, it would be the massive gas and dust clouds collapsing.
According to the widely accepted theory of galaxy formation known as the hierarchical model, galaxies form through the gradual and slow collapse of massive gas and dust clouds under the influence of gravity. As these clouds collapse, their material begins to condense and concentrate in certain regions, forming dense clumps.
These clumps then continue to attract more gas and dust through gravitational forces, causing further collapse and fragmentation. Over time, smaller clumps merge together due to their gravitational attraction, gradually forming larger and more massive clumps.
Therefore, the initial formation of galaxies is primarily driven by the collapse of massive gas and dust clouds, which leads to the accumulation of material necessary for the subsequent stages of galaxy evolution. The force of orbiting stars generating collisions and gravity acting on existing material are important factors in the later stages of galaxy evolution, helping to shape and structure galaxies once they have already formed.
For the theories describing galaxy evolution, one essential factor to the initial formation of galaxies is the massive gas and dust clouds collapsing. These clouds of gas and dust can accumulate due to various processes like supernovae, interstellar winds, and gravitational interactions. As the clouds collapse under their own gravity, they start to form regions of higher density, eventually leading to the formation of stars and galaxies. This process is known as gravitational collapse and is a crucial step in the formation of galaxies.
The factor that is essential to the initial formation of galaxies, according to either of the theories describing galaxy evolution, is the collapse of massive gas and dust clouds. Let me explain how this process occurs:
1. Massive Gas and Dust Clouds: Galaxies start forming from enormous clouds of gas and dust present in the early universe. These clouds consist of various elements, including hydrogen and helium, as well as heavier elements produced by previous generations of stars.
2. Gravitational Instability: Within these gas and dust clouds, there are regions where gravity causes the material to come together. As the cloud becomes denser due to its own gravity, it starts to collapse under its own weight. This process is called gravitational instability.
3. Fragmentation: As the collapse continues, the cloud breaks up into smaller fragments or clumps of material. These clumps are often referred to as protogalactic or primordial galaxies. Each of these clumps has the potential to form a new galaxy.
4. Merger of Clumps: Over time, these smaller clumps of material merge with each other due to gravitational attraction. The merger of smaller clumps into larger clumps is a crucial step in the formation of galaxies. It brings together more mass and increases the size of the proto-galaxy.
5. Separation Into Distinct Structures: As the merger process continues, the gas and dust within the proto-galaxy start to settle into a rotating disk shape due to conservation of angular momentum. This rotating disk gradually forms distinct structures, such as spiral arms or an elliptical shape, depending on the initial conditions and mechanisms involved.
Overall, the collapse of massive gas and dust clouds, the merger of smaller clumps, and gravitational forces acting on the existing material are all fundamental to the initial formation of galaxies, as described by theories of galaxy evolution.