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Fraction of the Universe

Understanding types of galaxies

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Galaxy

• A galaxy is a huge group of single stars, star systems, star clusters, dust, and gas bound together by gravity.

• Galaxies are larger than solar systems.– Our Milky Way galaxy is about 100,000 times the

size of our solar system.– Distances between galaxies are also very large…

light years.

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Types of Galaxies

• Spiral galaxy• Barred-spiral galaxy• Elliptical galaxy• Irregular galaxy– Take a moment to discuss these terms with your

neighbor. Why do you think these galaxies are given these titles?

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Spiral Galaxy

• Looks like a pinwheel or satellite image of a hurricane

• Large bulge in the center and arms that spiral outward– arms contain gas, dust, and many bright young

stars– most new stars form in the arms

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Barred-Spiral Galaxy

• Similar to spiral galaxy• Just what the name implies• Has a bar running through the center• Contains a band of bright stars emerging from

the center and running across the middle of the entire galaxy

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Elliptical Galaxy

• Looks like a round or flattened ball• Contains billions of stars, but little gas and

dust• Stars are no longer forming• Contain only old stars

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Irregular Galaxy

• Has no specific shape or organization• Smaller galaxies• Contain young stars and a lot of gas and dust• Able to form new stars

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Can you identify galaxies?

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Questions?

• What are some things that you would like to know about galaxies?

• Write your question on a post it note and place it on the board.

• After posting your question, you can take a quick break so that we can regroup.