EvolutioEvolution of n of

StarsStars

Main Factor Main Factor of Life Cycleof Life Cycle

•Beginning mass

NebulaeNebulae•Huge clouds of dust and gas

ProtostarProtostar•Hot, contracting cloud of dust and gases

•When the temp. reaches 10,000,000 °C, a star is born

Medium-Medium-sized Starssized Stars

•Most common star type

•Our sun

Red GiantRed Giant•Most of the hydrogen is used up

•Outer shell begins to expand

•As it expands, it cools and becomes red

•Core gets hotter – up to 200,000,000 °C – where helium is fused into carbon

•Gas drifts off forming a planetary nebula

White DwarfWhite Dwarf•Extremely dense•White hot

Massive Massive StarsStars

•Start like medium-sized stars

•Become supergiants after red giant stage

•Temp can reach 600,000,000 °C

•Carbon atoms fuse and eventually form iron

SupernovaSupernova•Tremendous explosion

•Heat can reach 1,000,000,000 °C

•Iron atoms fuse to form heavier elements

•Can light up our sky

Neutron Neutron StarsStars

•Often less than 16 km in diameter

•Spin very rapidly

•Energy is given off in narrow beams

•Pulsars – appear to give off pulses of energy

Black HolesBlack Holes•Incredibly massive stars

•Gravity becomes so strong that even light cannot escape