Life Cycle of a Star

Life Cycle of a Star like the Sun Mass is similar to the sun

Nebula Protostar Main Sequence Red giant White dwarf Planetary nebula Black dwarf Life Cycle of a Star like our Sun (Mass like our Sun)

Nebula Large area of gas and dust where stars are born Mainly hydrogen and helium Many light years across May eventually begin to collapse due to gravity

Protostar Nebula collapses Gases heat up due to friction and compression of gases No nuclear fusion

Main sequence star Star like our sun Fusion reaction – hydrogen is converted to helium and energy Star in balance – energy (gas pressure) is in balance with gravity Longest star stage Most stable

Gravity Energy (gas pressure) Energy and Gravity in balance in Main Sequence Star

Sun – Typical Main Sequence Star

Red Giant Stage Hydrogen fusion stops Core collapses and helium fusion starts (helium converted to carbon) Star expands and cools 10 times as big as the sun

A red giant during its collapse will often shed its outer gases in what is called a planetary nebula

White Dwarf Helium fusion stops and red giant collapses Small, dense, hot star remains No fusion but remains hot for millions of years

Nova A white dwarf will often go through a series of explosions called a nova Explosion will cause the star to be several thousand times brighter

Black dwarf End of stars with a mass similar to the sun

Follow-up Questions What is the difference between a protostar and a main sequence star? What are 3 ways a white dwarf is different than the sun? What are the forces that keep a star in balance? Which star has a longer life span, a red one or a blue one?

Life Cycle of a Star with a mass bigger than the sun

Main sequence Super Giant Supernova Neutron star Black hole The end to the very biggest stars (very biggest stars)

Super Giant Fusion goes beyond the helium fusion stage Up to1000 times bigger than the sun

Supernova Explosion of a Super Giant star Occurs after fusion stops and the star collapses on itself

Neutron Star Incredibly dense ball of neutrons About 10 miles across A spoonful would weigh 100 million tons Pulsar – a neutron star that emits two beams of radiation Can only be detected with a radio telescope

Pulsar On Pulsar off

Black Hole Huge stars collapse into an object with an infinite density Gravity is so great that not even light can escape Astronomers look for intense x-ray sources

Follow-up Questions What is the main characteristic that determines the end of stars? Why won’t the sun become a black hole? If we can not see a black hole, then how do astronomers know that they are out there.