Essay Sample on Galaxy Formation: Gravity, Matter, and Black Holes

Introduction

A galaxy describes a mass of moving matter stimulated by an external force in a more dynamic form. The force of gravity is the centre of formation in which material including gases and dust, are held together firmly. Consequently, the amount of energy acting on the content dictates size the galaxy develops. For bigger galaxies, the acting force is so great, forming a solid tug which attracts anything that comes closer through compression, this region defines the black hole (Conselice, 3). Considering the manner of formation, the number of galaxies in the universe is infinite but with a similar mode of creation. Therefore, this paper will be able to provide an in-depth analysis of galaxies, including, types, galactic mergers, dark matter, and origin of galaxies.

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Types of Galaxies

For decades, the only known galaxies types were the Milky Way which describes the cloudy nature they exhibited when observed by astronomers. In such, they were classified as nebulae since there were no other discoveries; however, further exploration in 1920 showed that nebula was an independent galaxy raising suspicion on the number of galaxies in the universe. Despite the long distance between the Milky Way and the nebula, the orientation from where it receives its light energy seems to bring some confusion on whether to classify it as an impendent galaxy or not.

During the period between 1920 and 1936, there was a scientific argument about galaxies resulting in more discoveries and classifications. Depending on the amount of force of gravity, galaxies acquired different sizes and shapes, classifying them into four categories. The constellations can either be elliptical, irregular, and lenticular or spiral (Román, Javier, & Ignacio Trujillo, 3). Among the various types of galaxies, the spiral type is the most commonly described as having a flat shape containing a central spinning bulge. The elliptical types are the second most observed galaxies. As their names suggest, their formation is affected by the spinning velocity affected by the force of gravity. Since the force acting on them is quite smaller as the one on spirals, elliptical galaxies obtain the shape of a globe. Giant galaxies take oval shapes with some containing billions of stars. However, there exist these type of galaxy formation which are smaller in size commonly described as dwarf galaxies. The unique characteristics of these types of galaxies, including dust content within them, star with defined spirals in orbits but lacking a definite direction explains non-existence of life in them.

The lenticular type of galaxy falls between the formation of spiral and elliptical galaxies. The innate nature of formation force in these galaxies gives them their unique shapes when observed. In such, when found, they look like lenses exhibiting both the characteristic of elliptical as well as spiral ones. These kinds of galaxies possess less dust; some contain a thin disk and a central bulge due to rotation. Besides these, due to the different forces acting on them, they tend to cluster more often in an area with a lot of matter where their effect can be realized. According to astronomical observations, the last type of galaxies is the irregular ones. Their characteristic gives them to distinction hence classified as irregular; by these, they show no associated relation with other types of galaxies. More often, these are normal galaxies which form as either elliptical, spiral, or lenticular but have a less gravitational force to sustain their proper spinning providing an avenue in which other external forces act. As other galaxies around gravitate, they generate additional forces which act on weaker galaxies hence forming irregular galaxies (Román et al., 7).

Galactic Clusters

The forces of gravities exiting within the individual galaxies mutually attract each other developing clusters. Formation of groups in the universe can take billions of light-years while other millions of light-years hence describe the form in which a group will take. For these reasons, galaxy clusters can either be poor or rich depending on the number of years the cluster has decided to accumulate galaxies and the number of galaxies within the groups (Adamo, Angela, & Nate Bastian, 2). Thus, different clusters are assigned distinctive names to distinguish them from each other such as the local group, Virgo cluster, and Virgo supercluster. As the names suggest, the local group represents a group of a cluster in which the number of galaxies is limited. For instance, the local group in which our planet belongs has less than 100 galaxies among them having 19 being irregular while 17 of them being dwarf elliptical. Since the period matters a lot in the accumulation of the universe in a cluster, the local group is thought to have three or less million light-years (Adamo et al., 5). In the local group cluster, only two galaxies are dominant; the milky way and the Andromeda. The two galaxies then attract the rest with their gravitational forces forcing them to orbit around them. The smaller the galaxy, the more attractive they are to larger ones hence smaller one is likely to be observed by astronomers than bigger ones which tend to large behind.

The Virgo cluster represents a group of galaxies which are moderately rich in content. They lie between the local group clusters and the Virgo supercluster hence are denser than the local cluster but less than the super bunch (Adamo et al., 6). By observation, this kind of clustering has more than a hundred galaxies joined together by an attraction force. Besides, the majority of the galaxies in these clusters are either spirals or irregular having no defined arrangement. Because these categories of cluster accumulate a large number of galaxies entirely, they are thought to have been developed for approximately 55 million light-years (Adamo et al., 6). Accordingly, the Virgo supercluster represents the oldest and the wealthiest galaxy cluster which has developed for many years. By observing its content, these clusters reveal that over one thousand galaxies are merged and thought to have originated for over three hundred million years from the local group. Since massive galaxies are more likely to attract smaller ones, the Virgo supercluster has two major galaxies; NGC 4889 and the NGC 4874 that dominate by attracting all other smaller galaxies around them. The force of gravity exhibited by these two giant galaxies within the Virgo supercluster is so great that smaller galaxies can never escape hence their orientation and arrangement are dependent on forces within individual galaxies that dictate their types. Elliptical galaxies tend to orient themselves in the central regions of the cluster while the spirals at peripherals.

Galaxy Dark Matter

Galaxies move, the spins around within their respective clusters. The velocity measure of motion the galaxies exhibit are useful in determining the density of a group. In such, galaxies that are observed to be moving at high speeds are more likely to be lighter than those running at a slower rate (He Jian-hua et al., 3). By observing these, galaxies which are moving fast may have acquired additional forces enhancing their motions or are either light to be driven by moved by gravity at such speeds. In such a case, extra powers are drawn from the dark matter exiting within the galaxies. Since galaxies are composed of hot moving particles (dust and gases), there is built up of friction enhancing the heat to the extent of emitting of X-rays.

Origin of Galaxies

The development of universe marks the beginning of galaxies as has been in the big bang theory. In such, the universe had existed as one body which explodes to release particles and energies. These particles later maintain the original motion directed by their energies. As these particles move around, the central region becomes more compact, attracting more and more particles forming a hole of dark matter which in turn supply extra energy for gravitation. The dark matter in the rotating particles provides energy aiding motion which later translates attracting more materials forming a galaxy.

Conclusion

Galaxies are mass of moving particles more gravitationally. The formation of galaxies is thought by astronomers to have begun with a big bang explosion. Galaxies are categorized into four types; spiral, elliptical, irregular, and lenticular. Furthermore, basing on the organization and the number of years galaxies are formed, they are classified into clusters as either Local groups, Virgo cluster, or Virgo superclusters.

Work cited

Adamo, Angela, and Nate Bastian. "The lifecycle of clusters in galaxies." The Birth of Star Clusters. Springer, Cham, 2018. 91-118. Accessed from https://arxiv.org/pdf/1511.08212.pdf

Conselice, Christopher J., et al. "The evolution of galaxy number density at z< 8 and its implications." The Astrophysical Journal 830.2 (2016): 83. Accessed from https://arxiv.org/pdf/1607.03909.pdf

Forbes, Duncan A., et al. "Globular clusters in Coma cluster ultra-diffuse galaxies (UDGs): evidence for two types of UDG?" Monthly Notices of the Royal Astronomical Society 492.4 (2020): 4874-4883. Accessed from https://arxiv.org/pdf/2001.10031.pdf

He Jianhua, et al. "No evidence for modifications of gravity from galaxy motions on cosmological scales." Nature Astronomy 2.12 (2018): 967-972. Accessed from https://arxiv.org/ftp/arxiv/papers/1809/1809.09019.pdf

Román, Javier, and Ignacio Trujillo. "Ultra-diffuse galaxies outside clusters: clues to their formation and evolution." Monthly Notices of the Royal Astronomical Society 468.4 (2017): 4039-4047. Accessed from https://arxiv.org/pdf/1610.08980.pdf