stellar evolution. ngc 3603 bok globules and giant gaseous pillars (evidence of embryonic stars),...

Stellar EvolutionStellar Evolution

Stellar EvolutionNGC 3603

Bok globules and giant gaseous pillars (evidence of embryonic stars),

circumstellar disks around young stars

progressing to aging, massive stars in a young starburst cluster

blue super-giant with its ring and bipolar outflowmarks the end of the life cycle.

STAGE ONESTAGE ONE

Stars begin as a NEBULA - a dark cloud of gas and dust

Made mostly of hydrogen and helium with small amounts of heavier elements

Eagle NebulaM16

Horse Head Nebula Horse Head Nebula

Veil Nebula Trifid Nebula

Thackeray's Globules in IC 2944

Omega or Swan Nebula

Ghost Head NebulaGhost Head Nebula

The nebula begins to contract and gravitational attraction increases

It continues shrinking and starts to spin.

Eventually it forms a flat disk with a PROTOSTAR in the middle

Planetary Disks Forming

STAGE TWO - Main STAGE TWO - Main SequenceSequence

Longest part Energy is produced as fusion take place in

the core of the star The energy from fusion balances the force

of gravity and makes it a very stable stage

Stage ThreeStage Three

Happens when almost all of the hydrogen atoms have fused into helium atoms

The core contracts due to the force of gravity

This increases the temp and causes the helium to fuse into carbon

This gives off a lot of energy and the star swells up to a giant or supergiant star

Stage FourStage Four

Helium fusion ends The star loses its outer

gases and reveals a core

An expanding shell of gases shed by this dying star forms a PLANETARY NEBULA

Ant Nebula

Helix NebulaHelix Nebula

Stingray nebula (Hen-1357), the youngest Stingray nebula (Hen-1357), the youngest known planetary nebula. known planetary nebula.

The "Spirograph" NebulaThe "Spirograph" Nebula

Cat’s Eye Nebula

The star collapses inward and forms a hot dense core of matter called a WHITE DWARF

Some white dwarfs may explode into a NOVA while they are cooling

What about really BIG What about really BIG stars??stars??

Stars with masses 10 -100 times greater than the sun can produce a huge explosion called a SUPERNOVA

SN1987A

What happens after the What happens after the explosion?explosion?

The core may contract into a very small, dense ball of neutrons called a NEUTRON STAR –

               If it rotates it is called a PULSAR

Really large stars contract with greater force and become a BLACK HOLE

Centaurus A (Hidden Black Hole)Centaurus A (Hidden Black Hole)

Classifying StarsClassifying Stars

Hertzsprung-Russell (HR) Diagram

Plots temp. v. luminosity

Most stars are main sequence