Essay, Research Paper: Galaxies

When you look at a distant galaxy, you are not only seeing into space, but far into the past as well. The light from one of the galaxies we see today actually started its journey toward Earth more than two – million years ago.
The discovery of galaxies [1] began in the early 1400’s by Polish astronomers and continues to be studied today. Knowing as we do today that the universe is amenable to investigation, and that telescopes can examine millions of galaxies at distances of millions of light – years. [2] Though they shine with light of many billions of suns, most galaxies are so distant that they look faint. There are only three galaxies visible to the naked eye from the surface of the earth. These are the two Magellanic Clouds, which lie in the southern skies and the Andromeda Galaxy, whose tenuous glow was aptly described by a seventeenth – century observer.
The form and variety of galaxies differ in size and mass. Normal galaxies or, often-called spiral galaxies are mostly large. The general anatomy can be described in three ways: a central region or elliptical (based on the shape and centered upon the nucleus), and a spherical corona or halo, composed primarily of old dwarf stars [3] and a globular cluster [4]. Spiral galaxies are probably formed from giant clouds of rapidly spinning hydrogen gases. Some of the gases pulled to the center by gravity and condensed into stars. The rotating disk of gases and stars form arms [5] and that is what gives the galaxy its spiral shape.
Elliptical galaxies far outnumber the spiral galaxies. An elliptical galaxy looks like a squashed ball. The Centaurus A [6] is an elliptical galaxy. It is one of the brightest and largest galaxies known, with three times as many stars as our galaxy. Scientist think that the center of this galaxy is experiencing giant explosions of million of stars hurling out clouds of hot gas. The central region is hidden by a dark band made of dust and gas.
Our sun and its planets lie in the environs of the Milky Way Galaxy. The Milky Way is formed by billions of stars. It is something that resembles a path or river result due to the fact that like any other normal spiral galaxies it is flattened in form. The light of The Milky Way is more intense in one direction, toward the constellation [7] Sagittarius in the southern skies of Earth. Dark rifts meander through the Milky Way. We now know that dark cloud of dust and gas that blocks the light from the stars that lie beyond them.
The structure of the Milky Way is a flattened disk that we know now to be the disk of our galaxy. Its appearance from our vantage point is that of a broad river of light stretching across the sky and glowing with the combined lights of myriad stars. The Milky Way lies toward the center of our galaxy. Our sun is more than halfway of our galaxy, so the richest star fields from our vantage points are those we see when we look back towards the center.
The Local Group is the nearest galaxies to us. They are called the Magellanic Clouds. They are called Magellanic by virtue of them having been introduced to the western civilization by the crew of Ferdinand Magellan. Their discovery made it possible to establish the clouds that were too distant to be part of our galaxy. The large Magellanic Cloud is about 150,000 light years, the small Magellanic Cloud is about 250,000 light years from the sun. Less than 100,00 light years separate, the two clouds.
The orbit of the Magellanic Clouds lie well within the gravitational field of our galaxy and orbits it as satellites. This arrangement of small galaxies playing court to large one is common in the universe. The spiral like the Milky Way plays host of several satellites. The orbit of the Magellanic Clouds are larger than others. The large cloud have about fifteen billion stars and the small has about five billion. The orbits of the Magellanic Cloud are marked by an enormous river of cold hydrogen gases, the Magellanic Stream. [8]
The Andromeda galaxy and the Milky Way constitute an example of one of nature most grandiose creation, that is a pair of spiral galaxies. The Andromeda is the largest of the pair and has about twice the mass of the Milky Way. They rotate in complementary (one clockwise and the other is rotating counterclockwise) directions. This characteristics of their relationship, found in many other pairs of spirals lends support to the hypothesis that the two galaxies formed at or around the same time.
Similarities between the two galaxies are abundant. Both are at a central region composed mostly of old stars and expansive flat disk populated by tens of billions of stars of widely assorted ages and chemical compositions cause dust – laden spiral arms. Each galaxy is attended by two prominent satellite galaxies plus less prominent satellites. The plane of each galaxy is inclined to the other at almost the same angle.
With the discoveries that are made each day, this will bring us closer to knowing more about our great, mysterious galaxy. The future holds many answers to ours question about our galaxy. How many galaxies are out there? Scientist suggest there are more than five billions galaxies. Perhaps there are other universes out there, maybe even different life - forms. The discoveries in our universe will never stop.
Galaxies
Any of numerous large – scale aggregates of stars, gas, and dust that constitute the universe containing an average of 100 billion solar masses and ranging in diameter from 1500 to 300,00 light years.
Light Years
The distance that light travels in a vacuum in one year, approximately 9.46 trillion kilometers or 5.88 trillion miles.
Dwarf Stars
A star, such as the sun, having relatively low mass, small size and average or below average luminosity.
Globular Cluster a system of star generally smaller in size than a galaxy, that is more or less globular in conformation
Arms
The rotating disk of gas that gives the galaxy its spiral shape
Centaurus A
A constellation in the Southern Hemisphere
Constellation
A orbitrary formation of stars perceived as a figure or design especially one of the eighty-eight recognized groups named after characters from classical mythology and various common animals and objects.
Magellanic Stream
Orbit of the Magellanic Clouds that are marked by an enormous river of cold hydrogen gas.


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