Describe how astronomers determined first, that our galaxy is a spiral, and then, how they figured out its a barred spiral.

Choose one of the following topics to discuss.

1. Describe how astronomers determined first, that our galaxy is a spiral, and then, how they figured out its a barred spiral.

2. Describe the Hubble Tuning Fork diagram and how its used in astronomy.

3. Explain how astronomers know that the majority of the matter in our Milky Way galaxy is composed of dark matter.

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