Download Stellar Evolution Slideshow

eagle nebula movie
H-R Diagram
(Oh yeah, you’re gonna see it again!)
Interstellar cloud of gas and dust – Birthplaces of stars!
Star Birth (Indie-RockSTARS like
our Sun)

Protostar – Stage 1. Gas and dust
collapses on itself by gravity,
balanced by outward gas pressure.
• Inward gas pressure trying to escape,
causing internal temp. & press. to rise

This causes nuclear fusion to begin!
Star Birth
Main Sequence
Fully developed star (like our sun)
-most of stars lifetime spent in this stage
Senior Citizen Stars

Later in life, stars
become Red Giants
• Star has converted
all Hydrogen into
Helium. Where is it
on H-R diagram?

Temp. drops, size
increases
Senior Citizen Stars

Variable Stars –
expand and
contract, grow
bright and fade.
• Over a period of 1 –
70 days

Quick for a star that
lasts ~10 billion
years!
Outer Shell Ejection


Later in life, a star will eject the
outer shell of Hydrogen, leaving the
Helium behind in the core.
This fast traveling Hydrogen gas is
called a Planetary nebula
IC-418
Eskimo Nebula
Ant nebula
NGC 7027
NGC 7662
Hourglass nebula
Helix nebula
Hi-ho, Hi-ho, It’s off to work….

After it’s shell is gone,
all that is left is a
layer of Helium, and a
core of denser
Carbon.
• Gravity pulls star
inwards

Results in very small,
very dense dying star,
a White Dwarf
• Low luminosity, low
temp.
R.I.P. Indie-RockSTAR


Eventually, White
Dwarf cools
further, turns red,
and dies.
It is now called a
Black (Brown)
Dwarf
Sun-like Life Cycle
Protostar
 Main Sequence
 Red Giant
 Variable Star
 Planetary Nebula (Ejection)
 White Dwarf
 Black Dwarf

What about Contract-RockSTARS?
(Massive stars)
Protostar
 Main Sequence
 Super Red Giant
 Variable Star
 Supernova
 Pulsar (Neutron Star)
 Black Hole

Supernova
Gigantic stellar explosion
 Carbon core temp. rises to 600
million K!

• That’s hot

Carbon fuses in the core, produces
Iron
• Fusion stops

Iron doesn’t fuse
Yeah…they’re pretty bright…
Crab Nebula

First noted by
Chinese
Astronomers in
1054
• A supernova
remnant!
We are all stardust….man..


Supernova ejection cloud travels
away quickly, and the intense heat,
pressure, electrons, etc. cause all the
heavier elements to form in the
universe.
So, really, we’re all formed from the
remains of stars!
• My head hurts now….
Pulsars (Neutron Stars)
After a star explodes, sometimes
only neutrons are left (Guess where
the name “Neutron Stars” came
from?)
 Also called Pulsars because they emit
radio waves with incredible
regularity.
 Appear to be rapidly rotating neutron
star

Pulsar
A slower pulsar
The crab pulsar
Yup, same one they saw in 1054!
Black Holes


Some REALLY big stars can
continue to collapse after
the pulsar stage to become
super dense areas of space
known as black holes
Simply a point in space
where gravity concentrates
a large mass into a very,
very small area
Black Holes


Surface of black holes, the point at
which no light can escape, is called
the Event Horizon
Spot in the center, in theory, is called
the Singularity
Black Holes
Schwarzschild Radius is the
theoretical radius at which a
spherical body becomes a black hole.
 R = 2GM/c^2

• G=gravitation constant M=mass
c=speed of light
Sun = 2 miles
 Earth = 1 cm (.4 inch)

Supernova recap

Supernova recap via Lite-Brite