Q:

Discovering Space: The Galaxies of the Universe?

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Quick Answer

A galaxy is a collection of stars, several billion of them, and their solar systems. A galaxy also consists of gas and dust. The planet Earth's solar system is part of the Milky Way galaxy.

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Full Answer

How Many Galaxies Exist in the Universe?
Some scientist believe that over 100 billion galaxies exist in the universe, as stated by the National Aeronautics and Space Administration. Other scientists would go further, saying there could be 200 billion galaxies.

In 2004, the Hubble Ultra Deep Field was created. A composite of two Hubble deep-space cameras, it showed 10,000 galaxies in a million-second exposure. This exposure covered only a small portion of the Fornax constellation. In 2012, with an upgraded telescope, 5,500 galaxies were discovered. As technology improves, more and more galaxies are expected to be discovered.

Despite all of the galaxies discovered thus far, there have been changes in what the Hubble Telescope has viewed over the years. This is because galaxies collide and become one. After data were analyzed, it was discovered that 10 times more galaxies existed in the early universe that have since merged into larger galaxies, according to Christopher Conselice of the University of Nottingham, UK

Not all galaxies look the same. Galaxy shapes are classified three different ways:

  • A spiral galaxy looks like a pinwheel, with long curved arms. The Milky Way Galaxy is a spiral galaxy.
  • An elliptical galaxy is oval shaped and is smooth in appearance.
  • Irregular galaxies are made up of various shapes that look like blobs fused together.
    • The Instruments That Discover Galaxies
      NASA launched the Hubble Space Telescope into space in 1990. Since then it has been updated several times. The latest shuttle mission to do updates on the Hubble Telescope occurred in 2009.

      With each update, the Hubble Telescope is able to see further into the universe. The latest technology, which allows the telescope to see deeper than ever before, has been labeled extreme Deep Field, or also known as XDF.

      No matter what type of instrument is used to discover galaxies, the same formula is used to calculate the number. This formula is based on Albert Einstein's theory of relativity. The number of galaxies is determined by taking the ratio of sky pictured by the telescope to the whole universe, and this gives a calculation of the number of galaxies.

      Some Facts About the Milky Way Galaxy
      The Earth's galactic home, the Milky Way is made up of many different facets. Some of the more obvious things that make up the galaxy are Earth, the sun and over a billion stars.

      The galaxy is made up of dust and gases and is held together by gravity. If a person were to view the Milky Way from above, the very center dot that can be seen is a supermassive black hole. This black hole has a very strong pull of gravity and is the largest type of black hole.

      This spiral-shaped galaxy has four arms, one of which, called the Orion Arm, holds the solar system and the sun. When measuring the Milky Way galaxy from the tip of one arm all the way across to the opposite arm, it is 100,000 light years across.

      The Milky Way is always on the move. It is constantly rotating in space and the arms move along with it. In fact, the solar system moves along with it at a speed of about 515,000 miles per hour.

      Learn more about Stellar Astronomy
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