1. Stars Presented by: Diana Sforza

2. What is a star? A star is a ball of gas held together by its own gravity.

3. Stars are made up of huge clouds of dust and gas collapse under gravitational forces, forming protostars. These young stars undergo further collapse, forming main sequence stars. Stars expand as they grow old. As the core runs out of hydrogen and then helium, the core contacts and the outer layers expand, cool, and become less bright

5. When a star reaches 27,000,000°F, Nuclear Fusion begins Nuclear Fusion is an atomic reaction in which many nuclei (the centers of atoms) combine together to make a larger one

6. A star goes through a phase called the Main Sequence. In there, there is a central band of stars which are formed after the stars energy is converted from Hydrogen to Helium.

7. The sun… …is a star

8. Other stars and their distance from the earth in light years Sirius8.6 Canopus74 Capella41 Rigel900 Vega25 Deneb1,500 Proxima Centauri4.3

9. Life span of a star A star stays in main sequence for about 10 billion years. After that, the hydrogen fuel is depleted and the star begins to die.

10. A star is part of a galaxy What is a galaxy??? A galaxy is a huge group of stars, dust, gas, and other celestial bodies bound together by gravitational forces.

11. They can be spiral. They can be elliptical. They can be irregularly shaped.

12. Milky Way Galaxy

13. Stars also make CONSTELLATIONS A constellation is a group of stars that, when seen from Earth, form a pattern. The stars in the sky are divided into 88 constellations.

14. WHY DO STARS TWINKLE? Stars twinkle when we see them from the Earth's surface because we are viewing them through thick layers of turbulent (moving) air in the Earth's atmosphere. For more information visit… Star Classification - Zoom Astronomy