Worksheet titled "Galaxies Worksheet" featuring questions about galaxy types, shapes, and classifications, including images of spiral, elliptical, and irregular galaxies.

Galaxies Worksheet Solution and Explanation

#### 1. How many galaxies are there in the universe?
- Answer: The exact number of galaxies in the universe is not known, but estimates suggest there are over 2 trillion galaxies.

#### 2. Match the type of galaxy with its shape.
- Spiral galaxy: a. Bulge in middle and arms that spiral outward
- Elliptical galaxy: c. Looks like round or flattened ball
- Irregular galaxy: b. Does not have a regular shape

#### 5. A young galaxy with a giant black hole at the center is a(n) _______.
- Answer: Active galactic nucleus (AGN) or Quasar
- Explanation: Young galaxies with active supermassive black holes at their centers are often classified as quasars or active galactic nuclei due to the intense energy output from the black hole's accretion disk.

#### 6. The galaxy in which our solar system is located is called the _______.
- Answer: Milky Way Galaxy
- Explanation: Our solar system resides within the Milky Way Galaxy, a large barred spiral galaxy.

#### 7. What type of galaxy is the Milky Way?
- Answer: Barred Spiral Galaxy
- Explanation: The Milky Way has a central bar structure and spiral arms, classifying it as a barred spiral galaxy.

#### 8. Suppose astronomers discover a galaxy that contains only old stars. What type of galaxy is it likely to be?
- Answer: Elliptical Galaxy
- Explanation: Elliptical galaxies typically contain older stars and lack ongoing star formation, making them composed mostly of old stellar populations.

#### 9–16. Classify each galaxy.
- Image 9: Elliptical Galaxy
- Image 10: Spiral Galaxy
- Image 11: Irregular Galaxy
- Image 12: Spiral Galaxy
- Image 13: Elliptical Galaxy
- Image 14: Spiral Galaxy
- Image 15: Spiral Galaxy
- Image 16: Elliptical Galaxy

#### 17–24. Complete the chart.
| Shape | Age of Stars | Size | Number of Galaxies |
|---------------|--------------------|---------------|---------------------|
| Spiral | Younger stars | Medium to Large | Most common |
| Elliptical | Older stars | Small to Large | Less common |

- Explanation:
- Spiral Galaxies: Typically have younger stars due to ongoing star formation in their spiral arms. They are medium to large in size and are the most common type of galaxy.
- Elliptical Galaxies: Generally contain older stars because they have little to no ongoing star formation. They can vary in size from small to large but are less common than spiral galaxies.

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Final Answer Summary:

1. Over 2 trillion galaxies.
2.
- Spiral galaxy: a.
- Elliptical galaxy: c.
- Irregular galaxy: b.
5. Active galactic nucleus (AGN) or Quasar.
6. Milky Way Galaxy.
7. Barred Spiral Galaxy.
8. Elliptical Galaxy.
9–16. Classification:
- Image 9: Elliptical Galaxy
- Image 10: Spiral Galaxy
- Image 11: Irregular Galaxy
- Image 12: Spiral Galaxy
- Image 13: Elliptical Galaxy
- Image 14: Spiral Galaxy
- Image 15: Spiral Galaxy
- Image 16: Elliptical Galaxy
17–24. Chart:
- Spiral: Younger stars, Medium to Large, Most common
- Elliptical: Older stars, Small to Large, Less common

Final Boxed Answers:
\boxed{
\text{1. Over 2 trillion galaxies.}
\text{2. Spiral galaxy: a, Elliptical galaxy: c, Irregular galaxy: b.}
\text{5. Active galactic nucleus (AGN) or Quasar.}
\text{6. Milky Way Galaxy.}
\text{7. Barred Spiral Galaxy.}
\text{8. Elliptical Galaxy.}
\text{9–16. Classification: See above.}
\text{17–24. Chart: See above.}
}