Galaxies are sprawling space systems composed of dust, gas, and countless stars. The number of galaxies cannot be counted the observable universe alone may contain 100 billion. Some of these distant systems are similar to our own Milky Way galaxy, while others are quite different. Galaxies with less than a billion stars are considered "small galaxies." In our own galaxy, the sun is just one of about 100 billion stars. Galaxies are classified into three main types: spiral galaxies, elliptical galaxies, and irregular galaxies.
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Spiral GalaxiesSpiral galaxies, such as the Milky Way, consist of a flat disk with a bulging center and surrounding spiral arms. The galaxy's disk includes stars, planets, dust, and gas, all of which rotate around the galactic center in a regular manner.
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ELLIPTICAL galaxiesElliptical galaxies are shaped as their name suggests. They are generally round but stretch longer along one axis than along the other. They may be nearly circular or so elongated that they take on a cigar like appearance.
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Irregular galaxies Irregular galaxies appear misshapen and lack a distinct form, often because they are within the gravitational influence of other galaxies close by.
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