The Life and Death of a Star

1. The Life and Death of a Star

2. Explain all life cycle of the stars. • Explain EMR. KEY WORDS Luminosity Main sequence Nebula Red dwarf Neutron Star Red giant White dwarf Supernova Red supergiant Black 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. Scientists have categorized stars according to their mass and temperature. • Small stars last longer(100 billion years) • Large stars are brighter but shorter-lived • (a few million years) 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.