1. Chapter 30 The Sun and Other Stars
Matter in our Universe

2. Chapter 30-1 How are stars formed?
Chapter 18-1 Vocabulary
Star- ball of gases that radiates light and heat.
Nebula- cloud of gas and dust in space.
Protostar- dense material in the center of a nebula that is about to become a star.
Star cluster- large group of stars that travel together through space.
*Our Sun is a star within our galaxy. There are billions of stars within our galaxy.
*There are billions of galaxies within the universe.
*Between stars and galaxies there are vast regions of empty space.
*Most of the stars in our galaxy are very distant. Many galaxies that exist are even further away.
*The size of a star usually dictates its outcome.
* Stars come in different colors, sizes, temperatures, brightness and composition.

3. Chapter 30-1
*Composition of a star consist of many different elements. Most stars are made up of hydrogen and helium. The most common is hydrogen. Other elements; sodium, calcium and iron.

4. Chapter 30-1Formation of Stars
Nebula’s are referred to as nurseries for stars.
* As the dust and gases contract causing the nebula to spin, this spinning dust and gas flattens into a disk.
*Materials in the center of the disk begin to form a protostar. As the nebula continues to contract, temperature and pressure build. This protostar eventually undergoes a nuclear reaction called “fusion”. This fusion gives off energy in the form of heat and light.

5. Chapter 30-1 Stars Double Stars and Star Clusters
Binary Star- pairs of stars that travel through space together and revolve around each other.
Star Clusters- many stars that move through space in large groups. These clusters come in various shapes; globular, round.

6. Chapter 18-2 Spectroscopy
Vocabulary
Spectrum- pattern of different colors of light coming from an object.
Spectrograph- device that measures the spectrum of an object.
Spectroscopy- study of light coming from objects in space.
*white light contains all wavelengths of visible light. Spectrum is the wavelength of that light broken down into individual wavelengths.

7. Chapter 18-2 Spectroscopy
Color and Composition
* A spectrum reveals the chemical make-up of a star. Scientist can study the spectral analysis of a stars light to determine the composition of a star.

8. Chapter 18-2 Color and Temperature
* The surface temperature of a star is related to its color.
*Blue stars are the hottest. (29,000°C – 40,000°C).
*Yellow stars are average temperature stars. (6,000°C).
*Red stars are the coolest. (2,100°C – 3,200°C).

9. Chapter 30-2 Magnitude of a Star
Brightness of a Star
Magnitude- way to measure a stars brightness.
* A stars brightness (magnitude) depends on; temperature, size and distance from the Earth.
* The hotter the brighter, the bigger it is the brighter it is, the closer it is to Earth the brighter it is.
Apparent Magnitude- The brightness of a star as seen from the Earth.
* Stars are placed on scale with the brightest stars (1st magnitude stars) receiving a low value and dimmer stars (4th magnitude stars) receiving a high value.
Absolute Magnitude- Describes the brightness of stars if all stars were brought to a distance of 32.6 light years from the Sun and compared.
* Stars with a low value are very bright (luminous). Stars with a high value are less bright.

10. Chapter 18-4 Classification of Stars
Star Classification
Main Sequence Stars- star that falls within a long, narrow, diagonal band across the Hertzsprung-Russell diagram.
* the Hertzsprug-Russell diagram or (H-R diagram) shows a relationship between a stars; surface temperature, color and absolute magnitude.
* simply stated; the brightness of most stars increases as the temperature increases.

11. Chapter 18-4 Other Stars (Anomalous Stars)
* Stars that do not fit into the main sequence category.
Red Giants- large, bright star that is fairly cool.
* appear in the upper right corner of the H-R diagram.
Supergiants- Stars that are very large, very bright (low absolute magnitudes) with relatively low temperatures.
*appear in the extreme right corner of the H-R diagram.
White Dwarf- very small, hot star.
*these stars are very hot with high absolute magnitudes and can be found in the lower left corner to center portion of the H-R diagrams. They can be blue or white.

12. Chapter 18-5 Stellar Life Cycle
Life Cycle of a Star
*Stars change over time.
* A stars life cycle takes millions of years.
* Stars change their mass into energy. Light and heat. This process is called fusion.
Protostar to Giant
* Stars are formed from a nebula. Gravity pulls the dust and gas together forming a protostar. If the protostar becomes hot enough, nuclear reactions begin to take place. Fusion changes hydrogen into helium. Large amounts of energy are produced.

13. Chapter 18-5 Protostar to Giant
* As hydrogen changes into helium the star continues to produce energy.
* When the process ends, small stars stop producing energy; stop shinning, contract to become white dwarfs.
* Larger stars will start new nuclear reactions that turn helium into carbon.
* This reaction expands the star and makes it cooler. It now becomes a red giant.

14. Chapter 18-5 Death of a Star *Depends on the size of the star.
Nova- explosion where the outer layers of a star are blown off.
Supernova- violent explosion where a star is blown apart.
Death of a Star
*Depends on the size of the star.
* Medium sized stars lose mass and begin to contract. (white dwarf)
* As a white dwarf cools and fades away, it now becomes a black dwarf.
* Sometimes the cool white dwarf will blow off its outer layer in a bright explosion called a nova.
* Massive sized stars expand and blow away their outer layers in a violent explosion. This process is called a supernova.
* Sometimes after the star blows away its outer layer, a small portion of very dense matter is left at the core to create a neutron star or black hole.

15. Chapter 18-5

16. Chapter 18-6 Earth’s Sun Structure of the Sun Sun’s Core
Core- Center of the Sun.
Photosphere- Inner layer of the Sun’s atmosphere.
Chromosphere- Layer of the Sun’s atmosphere above the photosphere.
Corona- outer layer of the Sun’s atmosphere.
* The Sun is an average star in size, mass and temperature.
* The Sun’s diameter is 1,400,000 km (Earth- 13,000 km).
* Made mostly of gases.
Sun’s Core
* The Sun’s core is located in the center of the Sun, accounts for 10% of its diameter, is where most of the Sun’s energy is formed and is extremely hot (15,000,000°C).
Sun’s Atmosphere (Makes up most of the Sun’s volume)
* Photosphere (light sphere)
* Visible layer of the Sun that gives off light.
* Chromosphere (color sphere) gives off a weak red glow.
* Corona (outermost layer) Extends for about 1,000,000 km from the Sun.
* Reaches a temperature of 1,500,000°C.

17. Chapter 18-6 Earth’s Sun
Diagrams of the Sun

18. Chapter 18-7 Surface of the Sun
Sunspots
Sunspots- dark, cool area on the Sun’s surface.
* Some areas on the Sun’s surface are cooler than other areas and don’t shine as brightly as the areas around them.
* Sunspots move in groups across the Sun’s surface as a result of the Sun’s rotation.
Prominence- stream of gas that shoots high above the Sun’s surface.
* Streams of flaming gas from the Sun’s surface.
* Huge arches, thousands of kilometers high that usually form in the chromosphere or photosphere.

19. Chapter 18-7 Surface of the Sun
Solar Flares- Eruption of electrically charged particles from the surface of the Sun.
* Build up of energy near sunspots that is released as a flare or sudden burst of energy. Electrically charged particles that are short term occurrences.
* Solar flares contain large amounts of energy that can disrupt communication satellites and create the auroras.

20. Chapter 18-8 How does the Sun produce energy
Solar Energy
* The Sun gives off energy in many forms, including heat and light.
* The Sun’s energy comes from nuclear reactions.
* This happens when the nuclei of atoms are changed.
Nucleus- center, or core of an atom.
Nuclear Fusion
Fusion- reaction in which atomic nuclei combine to form larger nuclei.
* The Sun is about 71% hydrogen and 27% helium.
* The temperature of the Sun’s center is about 15,000,000°C. At these temperature hydrogen atoms combine or fuse.

21. Chapter 18-8 Sun’s Energy Matter and Energy
* Albert Einstein helped explain how the Sun produces energy. Einstein said that matter can be changed into energy.
* The historical equation explains how a small amount of matter can be changed into a large amount of energy.
* E= energy, m=mass, c=speed of light
* Fusion energy is a possible future source of energy. Hydrogen found in the oceans, can be converted into helium, which releases large amounts of energy.

22. Chapter 18-9 Constellations
Star Patterns
Constellations- group of stars that form a pattern in the sky.
* Constellations are used to locate stars. There are about 88 constellations.
* Constellations are different in the Northern Hemisphere vs. Southern Hemisphere.
* Orion the Hunter- can be seen in the Northern Hemisphere from Nov.-Mar. Bright stars that can be found in Orion; Betelgeuse, Rigel.
* Ursa Major (Big Bear)- found in the Northern Sky, forms the big dipper.
* Ursa Minor (Little Bear)- found in the Northern Sky, forms the little dipper. The Star Polaris (North Star) can be found in this group.

23. Chapter 18-10 What are Galaxies
Galaxies- huge collection of stars, gas and dust that travels through space.
*Galaxies are building blocks of the Universe. There are billions of galaxies.
* Galaxies are classified by their shape.
* Galaxies are in motion
Elliptical Galaxy- galaxy shaped like a football.
* The stars in an elliptical galaxy are usually older. These galaxies are larger than irregular galaxies but smaller than spiral galaxies.
Irregular Galaxy- galaxy with no specific shape.
* Smaller and fainter galaxies. Most common type of galaxy.
Spiral Galaxy- galaxy shaped like a flattened disk with spiral arms.
* Usually have one or more spiral arms.
* The Sun belongs to a spiral galaxy called the Milky Way Galaxy.
* The Milky Way Galaxy belongs to a group of galaxies called the local group.
* The Milky Way Galaxy spans about 100,000 LY.
* The Sun is in one of the arms of the Milky Way Galaxy.
Galactic Neighbors
* Most galaxies are millions of light years from the Earth.
* The closest galaxies to Earth is the Magellanic clouds, which is an irregular galaxy some 160,000 LY.

24. Chapter Galaxies
Galaxies

25. Chapter 18-11The Universe Formation of the Universe
* The universe is everything, all forms of matter including the Sun. It is everything that exist in space, even space itself.
* It would take a space craft traveling at the speed light (300,000km/sec) about 10 billion years to cross space that astronomers can see with their telescopes.
Big Bang- explosion that began the universe billion years ago.
* About billion years ago, all the matter in the universe was contained in a pin size ball, that was very hot and dense. A huge explosion occurred causing the matter to be released.
* As the universe expanded from this point, it cooled, atoms and molecules formed and matter as we know it today eventually formed. (See reading)
Black Holes and Quasars
Black Hole- massive star that has collapsed and whose gravity is so powerful that it pulls in all matter including light.
* All the matter in a black hole is squeezed into an infinitely tiny point.
* Black holes are found at the center of galaxies.
* Can be millions of times heavier than stars.

26. Chapter the Universe
Quasars- Continuous burst of brilliant light and enormous energy from a massive black hole.
* Formed when matter falls into these black holes producing tremendous amounts of light and energy.
* Quasars are brighter than light coming from 1,000 galaxies.
Colliding Galaxies
* The whole universe is in motion.
* When galaxies collide they sometimes combine. This combining creates massive galaxies.