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Stellar Evolution
Stellar Evolution
NGC 3603
circumstellar disks around young stars
blue super-giant with
its ring and bipolar outflow
marks the end of the life cycle.
progressing to aging,
massive stars in a
young starburst cluster
Bok globules and giant gaseous pillars
(evidence of embryonic stars),
STAGE 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 Nebula
M16
Horse Head Nebula
Veil Nebula
Trifid Nebula
Thackeray's Globules in IC 2944
Omega or Swan Nebula
Ghost 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 Sequence
 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 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 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 Nebula
Stingray nebula (Hen-1357), the youngest
known planetary nebula.
The "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 stars??

Stars with masses 10 100 times greater than
the sun can produce a
huge explosion called
a SUPERNOVA
SN1987A
What happens after the
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)
Classifying Stars
Hertzsprung-Russell (HR) Diagram
Plots temp. v. luminosity
Most stars are main sequence