Download Stellar Evolution

Stellar Evolution
The Birth, Life, and Death of Stars
The Universe
• Everything
– All matter,
space, and
time
• The Universe
is 13.72
billion years
old
Cosmology
• The study of the
origin of the
Universe
• An average sized Star
• About 4.5 billion years old
The Sun
What is a Solar System?
• A star and everything that revolves around it
• Our Solar System is about ___ years old
A light-year
• A unit of
distance, not
time
• The distance
light travels
in one year
• 6 Trillion
miles
Distance to Sun
• 93 million
miles
• 8.3 lightminutes
Proxima Centauri
• The closest
star to our
sun
• About 4 lightyears away
Galaxies
• Stars are not
evenly
distributed in
space.
• They are in
groups called
Galaxies.
Types and Sizes of Galaxies
• Types: Elliptical, Spiral, Irregular
• Two sizes
– Giant
– Dwarf
•
• 100,000 light years across
• Has Hundreds of billions of stars
The
Milky
Way
Galaxy
Galaxy
Clusters
•A Group of
Galaxies
•Local Group
•2 mly across
•3 large &
about 2
dozen dwarf
•Andromeda
2.2 mly
Galaxy
Superclusters
• A cluster of
clusters
• The Local
(Virgo)
Supercluster
• 100 clusters
• 100 mly across
Nearest Superclusters
Galaxy Superclusters
The Visible Universe
How big is the Universe?
• The visible universe
is 28 billion light
years in diameter.
• Why is that all that
is visible?
• The entire universe
may be much
bigger
How
many
Galaxies
are
there?
• Hundreds
of billions
• Each has
hundreds
of billions
of stars
Edwin Hubble
• 1920’s
• Discovered
other galaxies
• Discovered
the Universe
is expanding
The Expanding Universe
• The Red
Shift
• Doppler
effect
The Doppler Effect
The Big Bang
• Tremendous
explosion
started the
expansion of
the universe
• All of the matter
and energy of
the universe
was contained
at one point
Characteristics of Stars
Star Properties and Classification
•
•
•
•
Color
Temperature
Age
Apparent
brightness
• Distance
from Earth
Star Brightness
• Apparent Magnitude
– How bright it looks
from Earth
• Absolute Magnitude
– How much light it
actually produces
Apparent Magnitude (Brightness)
• Depends
on actual
brightness
(luminosity)
and
distance
away
Hertzsprung-Russell (H-R)
Diagram
Compares a star’s Temperature (color) and its …
• Absolute
Magnitude
(Brightness
)
Hertzsprung-Russell (H-R) Diagram
Hertzsprung-Russell (H-R) Diagram
• Things to Know
• Color depends on temperature
– Blue, White, Yellow, Orange, Red
• The higher the Temperature the Brighter the
Star (if in the main sequence)
– White Dwarfs and Red Giants are exceptions
• The Sun is in the main sequence (90% of stars)
Star Relative Size
• The Sun is an averaged sized star
Stellar Evolution
The Formation and Life Cycle of
Stars
Star
Formation
• Originate in
gas clouds in
space called
Nebula
• Mostly
Hydrogen
• Gravity pulls
it together
Nebula
• The contraction
heats the gases
• When it gets hot
enough (27
million degrees)
nuclear fusion
starts
Nuclear Fusion
•Hydrogen nuclei are fused to make helium
• The
reaction
produce
s heat
energy,
which
causes
more
fusion
How big is a Nebula?
• The
Orion
Nebula
is about
2.5 light
years
across
Old Age
• When the hydrogen
runs low
• Contractions make
more heat
• Causes nuclear fusion
to make heavier
elements
• Expansion results in a
Red Giant
White Dwarf
• When energy is used, it shrinks to make a white dwarf
Supernovas
• Collapses abruptly
then explodes
• Billions of times
brighter
• Creates heavier
elements
• Occurs only in very
massive stars
After a Supernova
• The outer
layers are
blasted into
space to create
a new nebula
(starts the
cycle over)
• The core
collapses to
form a neutron
star
Neutron Star
• Left over
after a
supernova
• 1 teaspoon
weighs
billions of
tons
Black Holes
• A star
so
dense,
even
light
can
not
escape
Formation of Heavier Elements
• Elements
heavier than
hydrogen are
formed by
nuclear fusion
in Stars
• Elements
heavier then
iron form
during a
Supernova
The End