1. 8.8 A and B Components the Universe and the Sun
The student is expected to describe components of the universe, including stars, nebulae, and galaxies, and use models such as the Hertzsprung-Russell Diagram for classification.
AND
recognize that the Sun is a medium-sized star near the edge of a spiral- shaped galaxy of stars, and that the Sun is many thousands of times closer to Earth than any other star.

2. The Universe
The universe is all of space, time, matter, and energy that exist.

3. Components of the Universe-Galaxies
Billions of galaxies in the universe
Each galaxy contains billions of stars, dust, and gas.
Stars, gas and dust are held together in a galaxy by the force of gravity.
3 types of galaxies are spiral, elliptical, and irregular.

4. Milky Way Galaxy
Our solar system consists of the Sun, its planets, moons, and other celestial objects.
Our Sun is located in an outer arm of the Milky Way, which is a spiral galaxy.

5. Stars
A star is a large ball of gas that generates its own energy and is held together by its own gravity.
Stars fuse hydrogen gas into helium, releasing massive amounts of heat and light in the process.
Some are extremely hot; others are cooler. Some emit great amounts of energy; others emit less energy.
Stars may be young, middle-aged, old, or dying.
Some are very luminous (bright); others are dimmer.
Their colors range from blue and white to yellow and red

6. Stars
The stars in the universe are not all the same. Some are very large, whereas others are relatively small.
Some are extremely hot; others are cooler. Some emit great amounts of energy; others emit less energy.
Stars may be young, middle-aged, old, or dying.
They may be composed primarily of hydrogen, or they may contain mostly helium and heavier elements.
Some are very bright; others are dimmer.
Their colors range from blue and white to yellow and red.

7. Hertzsprung-Russell Diagram- a way to classify stars according to their luminosity, temperature, and color

8. H-R Diagram
Stars in the main sequence make up the vast majority of stars in the universe. In general, the hotter a star is on the main sequence, the brighter and bluer it is.
As stars age, they fall outside the main sequence and become giants or supergiants, depending on their mass.
As less-massive stars die, they become relatively tiny white dwarfs.
More massive stars die by exploding into a powerful supernova.

9. Life Cycle of Stars
Hot clouds of gaseous elements and compounds called nebulae serve as nurseries for stars.
As these nebulae spin, they slowly condense, raising their temperature and forming protostars, or beginning stars.

10. Life Cycle of Stars
Fill out the graphic organizer for the Life Cycle of Stars and glue into your notebook.
Note that the small/medium stars have a different cycle from massive stars, but they both begin as protostars in nebulae.

11. Practice with Hertzsprung Russell
Use the H-R diagram to answer the questions on the HR Worksheet.
Then answer the fundamental questions.

12. The Sun
Sun is a medium-sized star located near the edge of the Milky Way
The Sun appears brighter than any other star because it is many thousands of times closer to Earth than any other star.
The Sun is a yellow main sequence star.
According to the H-R diagram, the Sun’s surface temperature is between 5000K and 7500K
The Sun is the central gravitational point in our solar system

13. The Sun
It takes about 8.3 minutes for light from the Sun to travel the approximately 150 million kilometer distance between the Sun and Earth.
Light from all other stars takes much longer to reach Earth because the Sun is many thousands of times closer to Earth than any other star.

14. Fundamental Questions:
What are the components of the universe?
What are the components of a galaxy?
What are the 3 main types of galaxies and what is the name of our galaxy?
Where are we located within the Milky Way?

15. Fundamental Questions:
What are nebulae and why are they important to the life cycle of a star?
What is the first stage of any star’s life cycle?
Describe the life cycle for a small/medium star.

16. Fundamental Questions
Describe the life cycle of a large star.
What gaseous element fuels a star through nuclear fusion, and what type of gas does it become?
What 3 characteristics are used to classify stars on the H-R diagram?
What have scientists learned about stars by classifying them on the H-R diagram?

17. Fundamental Questions
The Sun is a medium sized, main sequence star. Describe its location on the H-R diagram in terms of luminosity, temperature, and color.
Why does the Sun appear brighter to us than all other stars?
How long does it take for the light emitted from the Sun to reach the Earth?