The Life Cycle of Stars (Text Ref. Page 375-382)

Learning goals We are learning how stars are created or born. We are learning to identify the stages of a stars lifecycle.

The Life Cycle of a Star the life cycle of a star is determined by its mass

Birth & Early Life all stars begin from a nebula which is a massive cloud of interstellar gas and dust

Birth and early life parts of the nebula collapse on themselves creating a stronger gravitational force as gravity increases more gas and dust is pulled in eventually forming a protostar

Birth and early life a protostar is a massive concentration of gas and dust

Birth and early life as the mass and gravity increases, it becomes a tightly packed sphere of matter atoms in core become so tightly packed the pressure rises and nuclear fusion begins (H atoms fuse to form He atoms)

Birth & Early Life outward pressure from the core and the gravity pulling toward the centre of the star counteract star stabilizes at a particular size

Hertzsprung-Russell Diagram Hertzsprung-Russell Diagram plots absolute magnitude against star surface temperature

Main Sequence Phase 90% of stars fit in the main sequence on the Hertzsprung-Russell Diagram a star spends the majority of its life as a main sequence star undergoing nuclear fusion until its hydrogen is used up

Main Sequence Phase a star then becomes a red giant or a red super giant depending on its mass

Old Age a star with a mass equal to or less than the Sun becomes a Red Giant red giant: a large, red star at/or near the end of its life cycle

Old Age a star with a mass greater than the Sun becomes a red Supergiant

The Death of a Star A star that has the same or lesser mass than the sun becomes a white dwarf

Stars like the Sun white dwarf: a small, hot, dim star the white dwarf becomes dimmer and dimmer until the light goes out

The Death of a Star A star that has a bigger mass than the Sun becomes a supernova then either a neutron star or a black hole

Stars Bigger than the Sun supernova: a stellar explosion that occurs at the end of a massive star’s life

Stars Bigger than the Sun neutron stars: an extremely dense star made up of tightly packed neutrons results when a massive star collapses

Stars Bigger than the Sun black hole: an extremely dense quantity of matter in space from which no light or matter can escape

Learning goals We are learning how stars are created or born. We are learning to identify the stages of a stars lifecycle.

Homework Page 382 questions 3, 4, 8 , 10