Galaxies Essay

                                                                                                                                                                                                                     The Galaxy                                                                                                             By Rick Costello                                                                                                                                                                                                          Our galaxy, is a group of stars that we named the Milky Way Galaxy. There are in our galaxy 100-400 billion stars.  Our star the Sun, is one star in our galaxy of 100-400 billion stars that revolve around the center of the galaxy once every 225 million years like a giant hurricane of stars. The Milky Way Galaxy is similar to a hurricane in that clouds forming spiral arms, rotate around the center or the eye of the hurricane. Our galaxy is very similar except instead of having spiral arms made of clouds of water vapor as a hurricane’s, our galaxy has spiral arms made of atoms of dusts gases, and stars, hundreds of billions of stars.

  When the Big Bang occurred, it created a huge blast of radiation which formed a tremendous amount of heat in the quickly expanding Universe. This heat and radiation formed Quarks and Gluons which later combined to form neutrons, protons throughout the early Universe. As the temperature cooled, it reach a temperature that forced the neutrons and protons to combine with each other to form nuclei.  400,000 years later, as the universe continued to cool, it reached a temperature that forced the nuclei to combine with an electron. When these combined they made the first elements in this Universe, hydrogen atoms. The Universe was filled with Hydrogen atoms. 

   The hydrogen gases all over the early Universe were pulled in separate groups forming enormous separate volumes of hydrogen atoms. These were the beginnings of the 500 billion separate galaxies in the Universe.  The atoms of hydrogen within these volumes then began colliding to form the stars in the galaxies.  Throughout it’s life, our galaxy will produce trillions of stars.  Stars live their lives then throw their matter into space in their death and new stars are formed from these gases.  In our time, our galaxy presently has between 100 and 400 billion stars and our galaxy is one galaxy in the Universe with 300 billion other galaxies.

 In this early Universe about 13 billion,700 million years ago, these atoms of hydrogen floating about started banging into each other and sticking to each other and began to grow larger and larger. The larger they got the effects of gravity started to take effect and the larger objects began to draw more atoms into them and they grew larger and larger. It can take as short as a few hundred thousand years for the balls of hydrogen gas to gather enough mass for the weight of the gases at the center to create such an enormous pressure that builds the temperature up high enough for it to force the hydrogen atoms to combine with each other forming a new element, helium. Each time 2 hydrogen atoms combine, it creates a photon of light and the star shines. Our star the Sun each second, converts 400,000 tons of hydrogen into the element helium.  The nuclear furnace in the interior of stars burn a few hundred million years for the giant stars, to over 60 billion years for the smaller red dwarf stars. The Sun is a middle of the road star and will burn in it’s present stage for 10 billion years.  So far the Sun is about half way through these 10 billion years. The Sun and our planets, moon’s, asteroids and comets are about 41/2 billion years old.                          

  The amount of stars in the whole Universe, in all 300 billion separate galaxies is an astounding number. Just for your imagination, imagine sitting on a beach and reaching down and picking up a handful of sand.  Imagine letting the the individual grains of sand trickle out as slow as you can, 10 or 20 at a time. Now imagine counting each individual grain of sand in your hand. Then imagine the number if you counted every grain of sand on the whole beach.  There are more stars in the Universe than individual grains of sand on every beach on our planet Earth.

   We live on the planet Earth, which revolves around the closest star to us the Sun.  The Sun is one star in this galaxy, a galaxy with 100 to 400 billion other stars.  Our galaxy is one galaxy in the Universe that contains hundreds of billions of other galaxies. 

  A light year is a measure of distance equal to just under 6 trillion miles   (5.9 trillion miles).  In one year light travels 6 trillion miles, hence a light year. Our galaxy is round and flat, kind of like a CD or an old 33 speed record with a bulge at the center, a collection of old stars circling the center of the galaxy around a black hole at the very center with the mass of 300 Sun’s.  Our galaxy has a diameter of 150,000 light years and is       30,000 light years thick. For the mileage of the diameter of the galaxy, multiply 6,000,000,000,000 m/l.yr. x 150,000 l.yrs.  It’s a lot of miles to the other side of the galaxy.  The closest star to us is 4.2 light years away. There are a lot of stars in this galaxy but this is also a huge galaxy. If you could stand on another planet anywhere in the galaxy, the stars in that night sky would appear just as far as they do in our night sky.  From our view there are great distances between the stars.  For distances in the Universe, these stars are but a stones throw.

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.


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


The rotating disk of gas that gives the galaxy its spiral shape

Centaurus A

A constellation in the Southern Hemisphere


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.

Word Count: 1093

0 thoughts on “Galaxies Essay”


Leave a Comment

Your email address will not be published. Required fields are marked *