Andromeda galaxy (photo: Mironovfoto).A galaxy is the largest object in the universe. It is made up of billions of stars, dust and gas. The pull of gravity holds a galaxy together. The earth is located within the Milky Way galaxy.

Photo: Andromeda Galaxy (Creative Commons: Mironovfoto).

Types of Galaxies

There are hundreds of billions of galaxies in the universe. One estimate is that there are 500 billion galaxies in the universe. A galaxy is a very large object. The smallest galaxy may have about 10 million stars. The largest galaxy may contain over a trillion stars.

Our solar system is located in the Milky Way galaxy. There about 400 billion stars in the Milky Way galaxy. It is considered a middle sized galaxy.

Galaxies are classified by their shape. The Milky Way is a spiral galaxy. There are three basic types of galaxies:

  • the spiral galaxies,
  • the elliptical galaxies, and
  • the irregular galaxies.

Origin of a Galaxy

Right after the Big Bang, the universe was uniform. At first, the universe was only gas. There were no galaxies at that time. Then, the universe slowly began to cool down. Gases began to condense into areas filled with dark matter. Gases such as hydrogen and helium began to form in these areas.

Slowly, these gases began to combine into stars. Large groups of stars made the first galaxy. The first galaxies began to appear when the universe was about 500 million years old.

Improving Your Reading and Thinking Skills

Think for a few moments. Try to recall the major ideas in this article. When you are done, click the box below for a list of main ideas.


How did you do? With practice, you should be able to identify many of the major ideas. You may even discover some important ideas that aren’t listed.


What Our Milky Way Galaxy Looked Like 11 Billion Years Ago.


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9 comments on "Galaxy: the Largest Object in the Universe"

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Ronand Abella

Ang mga bitwin ay meron sa galaxy.Ito nag papaliwanag sa mga tao na sa gabing raw.Ang mga ito ay nag papakita ng maramingmga bitwin sa ating mundo.

Ronand Abella

The earth can be located in a milky way.Milky way is considered a middle sized galaxy because of the stars it had 400 billion stars.The smallest galaxy has only 10 billions of stars.The oldest galaxy had over trillion of stars.

Webster Gabiana

Ang natutunan ko ay mga bitwin ay subra marami.

Webster Gabiana

I learned is are many star that shapes .
I learned is the earth located in the galaxy.
I learned that about the galaxy now i knew.

Webster Gabiana

Ang na tutunan ko ay mga na galaxy.