The galaxy


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: How it formed

is part of the entire universe. While there isarguably little knowledge about the entire universe, there have beenmajor debates about how it was formed. The most widely acceptedtheory about the formation of the universe is the big bang theory.The standard theory holds that the universe sprang into singularity,which is defined as a zone that defies the laws of physics. Justbefore the big bang event, black holes had formed, which are zones ofintense gravitational pressure and infinite density (Mayank &ampThakur, 2015). After this, the mass expanded and cooled rapidly.However, there has been a misleading misconception about the natureof formation of the galaxies. While some people think that it was anactual explosion, Trouille et al. (2013) assert that it was anexpansion that began billions of years ago, and is still going ontoday. When the matter from the big bang cooled down, it formedplanets, stars and other bodies that constitute the galaxy. Theearth, the moon, sun and other planets in the solar system are allbelieved to have been formed that way.

Figure1: , part of the entire universe. Source (,n.d).

Sizeand shape

According to Rucker (2013), no one knows if the universe isinfinitely large. However, the milky way galaxy is said to containabout 2000 billion stars. According to the big bang theory, thegalaxy is always expanding. The same thing is happening to thegalaxy. However, to put things in perspective, NASA measures the sizeof the galaxy according to light years. A light-year is the distancethat light travels in one year. The speed of light is 299,792,458m/s. is 980,000 light-years from end to end (Gamow, 2012).NASA says that the galaxy is a large spiral body, which forms in theshape of a disc (Taylor et al., 2012). The shape of the milky waygalaxy is almost the same as others that form the entire universe.


Just as the origin, size and the shape of the galaxy, its age is aswell a controversial issue. One of the underlying presumptions whenapproximating the age of the galaxy is that it cannot possibly beolder than the matter contained in it. Going by this, scientists havestudied the composition of the matter that makes up objects in theuniverse, such as meteors and space dust. In 2012, after studying theleftover radiation in NASA’s Wilkinson Microwave Anisotropy Probe(WMAP), scientists estimated the age of the galaxy to be 13.772billion years (, 2015). The error allowance of thisapproximation is only 60 million years, making the results reliable.Other figures that have been mentioned by scientists are 13.82billion and 13.88 billion. According to (2015), given thatthese figures fall under the 11 billion years that was obtained fromstudies on the globular clusters, these numbers are justifiable.

Figure2: Roadmap of background radiation of the Big Bang that scientistsuse to determine the age of the universe. Source (, 2015).


Perhaps the most widely and accurately studied topic about the galaxyand universe is its physical and chemical composition. One of themajor components of the galaxy is the massive gaseous matter thatfills up the intergalactic space, helium (Ryu et al., 2012). Modernscientists have studied the dark matter that is believed to make upalmost three-quarters of the universe. This substance is chemicallyand physically different from normal matter. It only interacts withgravity. Given that it does not reflect, emit or obstruct light, darkmatter is difficult to observe directly. Another intriguingcomposition of the galaxy is dark energy. The dark energy is used byscientist to explain the expansion of the universe, and existence ofenergy in the universe (Ryu et al., 2012). This is the energy thathelps the galaxy maintain its dynamic nature. Other elements thatmake up the composition of the galaxy are hydrogen (about 4%), stars(about 0.5%) Neutrons (about 0.3%) and heavy elements (about 0.03%).The heavy elements include planets like earth and the moons.

Figure3: Composition of the matter in the galaxy. Source (,2015).

Possibilityof life

So far, the only form of life that exists in the galaxy, according toknowledge of man, is on earth. Regardless, there have been numerousstudies to establish whatever there is life, intelligent or not, onother parts of it. According to Stephen Hawking, a renowned cosmologyspecialist, what is perceived as life is based on a chain of carbonatoms, and others such as nitrogen and phosphorous (Coustenis &ampEncrenaz, 2013). As such, there is a speculation that there can belife supported by another chemical basis, such as silicon. However,given the rich chemistry of carbon, it remains to be the most favoredelement to support life. This leads to a straight assumption thatthere is carbon on other parts of the galaxy, which was formed asthings cooled down following the Big Bang, meaning that there is thepossibility of life there. Moreover, there has been the argument ofthe DNA molecule, which is the basic element of intelligent life.Given evidence of DNA from about 500 million years ago as the earthwas cooling and stabilizing, scientists assume that there mightindeed be DNA on other parts of the galaxy too (Steele, David &ampTecchnau, 2011). However, the main challenge has been producing hardevidence about life on other parts of the galaxy.

Howto observe it

Given the expansive nature of the galaxy, observing it takesspecialized skills and modernized equipment. Apart from the partsthan can be observed using the naked eye, this equipment helpscientist to view into the deepest parts of space. Distance bodiesemit electromagnetic radiation, such as infrared and gamma rays,which are detected by these instruments (Schonfelder, 2013). Theseinstruments are optical telescopes, which are owned by spaceobservatories like NASA. To observe the galaxy on other platformsother than electromagnetic waves, for instance, radio waves, thereare specialized telescopes that are used. The images from theinstruments can be printed on normal paper after undergoinghigh-level editing and color correction. Below is a sample of animage taken by a space observatory.

Figure4: `White dwarfs` stars captured by Hubble space telescope. Source(, 2014).


As earlier explained, the universe is always expanding, following theBig Bang. The size of the universe at the moment of its formation wassmaller than now. As such, the galaxy is set to expand even more inthe future. The stars are expected to expand in size until the momentthey shall eventually degenerate. The same is expected for all otherheavenly bodies. The earth, for instance, is expected to evaporate inabout 10^49 years (Smolin, 2013). After the formation ofblack holes, the mass will decrease and begin becoming infinitelysmall after about 10^100 years. The black holes willeventually evaporate in what is referred to as a dark age. Afterthis, no known process is expected to change anything as it is knowntoday.

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Coustenis, A., &amp Encrenaz, T.(2013).&nbspLifeBeyond Earth: The Search for Habitable Worlds in the Universe.Cambridge University Press.

Gamow, G. (2012).&nbspThecreation of the universe.Courier Corporation.

Mayank, P., &amp Thakur, P.(2015). A Comparative Study of Modern Theories of Universe.&nbspJournalof Pure Applied and Industrial Physics,&nbsp5(7),223-230.

Rucker, R. (2013).&nbspInfinityand the Mind: The Science and Philosophy of the Infinite: The Scienceand Philosophy of the Infinite.Princeton University Press.

Ryu, D., Schleicher, D. R.,Treumann, R. A., Tsagas, C. G., &amp Widrow, L. M. (2012). Magneticfields in the Large-Scale Structure of the Universe.&nbspSpacescience reviews,&nbsp166(1-4),1-35.

Schönfelder, V. (Ed.). (2013).&nbspTheUniverse in gamma rays.Springer Science &amp Business Media.

Smolin, L. (2013).&nbspTimereborn: From the crisis in physics to the future of the universe.Houghton Mifflin Harcourt. (2015). How old is the universe? Retrieved on 12November 2015 from

Steele, R. E., David, C. N., &ampTechnau, U. (2011). A genomic view of 500 million years of cnidarianevolution.&nbspTrendsin genetics,&nbsp27(1),7-13.

Taylor, J. E., Massey, R. J.,Leauthaud, A., George, M. R., Rhodes, J., Kitching, T. D., &ampTanaka, M. (2012). Measuring the Geometry of the Universe from WeakGravitational Lensing behind Galaxy Groups in the HST COSMOSsurvey.&nbspTheAstrophysical Journal,&nbsp749(2),127. (n.d). The universe. [Image]. Retrieved 12November 2015 from

Trouille, L. E., Coble, K.,Cochran, G. L., Bailey, J. M., Camarillo, C. T., Nickerson, M. D., &ampCominsky, L. R. (2013). Investigating Student Ideas about CosmologyIII: Big Bang Theory, Expansion, Age, and History of the Universe.Astronomy EducationReview,&nbsp12(1).