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People have always been interested and fascinated by celestial bodies trying to attach some importance and divine extraordinary meaning to the processes they observed during the shifts of the day and night. There’s not so much time passed as people started to perceive astronomy as a branch of science and by now accumulated a considerable amount of galaxies, stars, comets, asteroids, and other cosmic bodies. By now a lot of observations about galaxies are available though outer space still puzzles peoples’ minds and leaves more questions than answers.
In this paper, I would like to give an overview of some galaxies, try to explain how they occur, coexist with other astronomical bodies, and focus on the Milky way in particular.
To commence with it is reasonable to provide a definition of a galaxy. The scientists provide different definitions of galaxies but they are all very similar. Thus, according to D. Moche “, a galaxy is an enormous group of millions of stars and gas and dust held together by the force of gravity” (147). J. Binney and M. Merrifield describe a galaxy as “a gravitationally-bound collection of stars” (1). The structure and the materials they are built of are very complicated. Galaxies can also amalgamate into more complex structures called “clusters” but it is the galaxies that serve as the basis for the Universe (Binney and Merrifield 1). It’s noteworthy that galaxies can be very small, containing few stars or just gases and huge clusters, consisting of stars, gases, dust, cosmic rays, and the like. H. Karttunen states that in the center of almost every galaxy should be “a compact nucleus” that may radiate bright light (Karttunen and Kroger 367).
There exist many classifications of galaxies, but the most widespread is the classification of galaxies in terms of their shape or “visual morphology” (Fanning and Menzel 167). Thus, galaxies may be of different patterns that are clearly distinguished through the astrometric telescope in the X-ray spectrum. The prevailing form of galaxies in outer space is the elliptical galaxy, i.e. having the shape of an ellipse. There exist also spiral galaxies, spherical, spiral, dwarfs, and other galaxies that present a complicated pattern of clusters, stars, and gas (National Research Council 39). It’s also known that galaxies consist of dust clouds that “absorb the visible light and turn it into radiation” (National Research Council 40).
For a long time, there was a belief that galaxies are stable congregations that don’t change over time. But in the 1970s the scientists found evidence that galaxies develop. It is difficult to observe for humans as the galaxies are situated millions and billions of light-years away from our planet, so we can see only the picture of the galaxy as it looked like million years from now. For example, a well-known Andromeda galaxy is 2 million years away and the Virgo cluster is 50 million years away from the earth (National Research Council 56). Still, with modern technology development, it is possible to find out the age, the chemical composition, and the speed galaxies evolve.
As it has already been mentioned some galaxies have a nucleus inside that radiates bright light and emits energetic beams. This assumption was proved in the 1960s “with the discovery of quasars” (National Research Council 56). However, it is assumed that the quasars do no longer exist in the galaxies but at earlier stages was a part of the evolutional process of galaxies. The reason they are still visible on the pictures from space is that it takes a huge amount of time for the light they produced to reach the Earth so now we see only the remnants of the quasars. But before they died they could have given birth to other galaxies by colliding into pieces and releasing huge amounts of energy that formed a new galaxy.
The galaxy the Earth belongs to is called Milky Way for it resembles the trail of spilled milk (Fanning and Menzel147). Milky Way is considered to be a giant galaxy that consists of about 200 billion stars including our Solar System with the Sun in the center. In addition, it consists of cosmic dust, gases, and nebulae. Our galaxy has the shape of a spiral, which means that it has a “nucleus”, a center in the location of Sagittarius, and “spiral arms” where all the stars are located (Fanning and Menzel 150). Besides, the galaxy includes not only separate stars but also clusters of stars. The age of the Milky Way is estimated at about 13 billion years. The neighboring galaxy is the Andromeda Galaxy that together with the Milky Way forms a binary system of giant spiral galaxies (Fanning and Menzel 165).
It is assumed that the Galaxy was formed when small galaxies, stars, gases, dark matter, and dust merged together with the help of gravitational energy, just some million years after the Big Bang. Our galaxy is the second-largest member of the Local Group and a very massive one (Clark 131).
As far as the Solar System is concerned we find it close to Orion’s arm. The sun is not the brightest star in the Galaxy.
Nowadays, there exist a lot of pictures of the galaxies like ours but the main difficulty that prevents us from getting more information is that the galaxies, especially, the centers are surrounded by masses of cosmic gases that blur the picture. Moreover, it is easier to get a picture of the far galaxy than our own. That is why it takes time and very precise modern astronomical equipment to get a clear picture. Despite this fact, the pictures the astronomers get at their disposal provide a lot of information about the celestial bodies, not to mention that the pictures are very colorful and reveal beautiful patterns of galaxies.
To conclude it’s necessary to mention that the interest of scientists in astronomic bodies never ceases and there are still a lot of blank spaces on the Universe map.
References
Binney, James, Merrifield, Michael. Galactic Astronomy. Princeton University Press, 1998.
Clark , Roger Nelson. Visual Astronomy of the Deep Sky. CUP Archive, 1990.
Fanning, Antony Edward, Menzel, Donald Howard. Planets, Stars and Galaxies: Descriptive Astronomy for Beginners. Courier Dover Publications, 1966.
Karttunen, Hannu, Kroger P. Fundamental Astronomy. Springer, 2007.
Moché, Dinah L. Astronomy: A Self-Teaching Guide. John Wiley and Sons, 2009.
National Research Council (U.S.). Astronomy and Astrophysics Survey Committee. The Decade of Discovery in Astronomy and Astrophysics. National Academies, 1991.
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