1. The Life and Death of a Star

2. Explain all life cycle of the stars. Explain EMR. KEY WORDS LuminosityMain sequence NebulaRed dwarfNeutron Star Red giantWhite dwarfSupernova Red supergiantBlack hole

3. The life of a star takes place over billions of years. Stars start out as nebulae Nebula – huge cloud of dust and gases. Nebula slowly collapse in to a star at the core that begins to release energy as a main sequence star. Stars release energy by nuclear fusion Fusion – two atomic nuclei fuses to form one new nucleus releasing energy. Fission – nuclear reactions in which an atomic nucleus break apart into two or more nuclei releasing energy.

5. Small stars last longer (100 billion years) Large stars are brighter but shorter-lived (a few million years) Scientists have categorized stars according to their mass and temperature. Small main sequence stars – Red Dwarfs Very cool temperatures of their outer gases. Ends its “life span” by forming a cool, dim star called a white dwarf. Fades out until it no longer emits light energy.

6. Remember – we can’t see most red dwarfs – they’re light is too weak.

7. Medium-sized stars – like the Sun Runs out of lighter elements for fusion. Core collapses then swells to produce a red giant. Red giant may fade out as white dwarf (smaller). Red giant may explode as a supernova leaving behind a neutron star (larger). “Pulsar” neutron star

8. Large main sequence stars Extremely large energy for a short period of time. Fuses heavier elements (iron) after lighter ones. At end, swells to form a red supergiant. Core may collapse in supernova to form a neutron star. Core may collapse into a black hole (largest) Nothing can escape the gravity pull of a black hole.