Transcript Stellar Evolution

Warm up
• The sun is 4.6 billion years old – how can
it continue to produce so much heat and
light?
Nuclear reactions
• Create new atoms – different elements
• Fission – splitting or decay
• Fusion – merging, combines
H fusion
• 4 H nuclei collide in a series of steps
resulting in 1 He nuclei and ENERGY!!!
Energy transfer
• Conduction – energy by direct contact
• Convection –heat transfer due to density
differences
• Radiation – floats away from the source
• Energy gets from the sun by radiation
• So do radio waves, UV, infrared, etc
Structure of the Sun
• Solar flare – a bright temporary outburst
of light and energy associated with
sunspots
• Solar prominence – a large gaseous
eruption from the chromosphere
Warm up
• If there are so many stars producing light,
why is the night sky so dark?
Light
• See the source - the flame, the light bulb,
the sun
• See the reflection
• Earth’s atmosphere has lots of stuff to
bounce off of
• Space doesn’t
Electromagnetic spectrum
• Radio waves, microwaves, infrared waves,
visible light, X-rays, and gamma rays are
all part of the electromagnetic spectrum.
• Help us know elements in stars
• Provide more information about stellar
activity
Composition
• Each element has a unique emission
spectrum
• Matching game
What objects can you see during
the day, night or both
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Moon
Sun
Stars
Planets
Which of these do you see every
night/day, every year, only once
Warm up
• What ways do stars differ from each
other?
• How is the Sun like other stars?
• How is the Sun unique?
How did the solar system start
• Like any other star, from a nebula etc
Stellar Evolution
(The series of changes matter goes
through in a star’s formation, life &
death.)
First random, spread out matter
Then a supernova explosion starts
things moving/compressing
Gravity will keep pulling things
together, generating heat & light
Nebula
• Places where stars form
• Protostars – hot, glowing points of light,
gravity is still compressing, rotation
• (Planetary systems may start forming)
• Forces include gravity (compression),
rotation, magnetism, pressure pulling apart
• Heat trapped inside
• 10 x 106 K Hydrogen FUSION BEGINS
Nebula
Main Sequence
• H fusion continues at
a steady rate
• On the H-R diagram
• As H runs out, He
fusion begins, leaves
main sequence
sun
• 4.5 billion years old (life as a main
sequence star)
• Middle aged
• 4.5 billion years left in the current form
Red giant
• Core collapsing, He fusion, He consumed, gravity pulling
tighter, Carbon, etc
• Shell expanding, heat from new nuclear reaction driving
shell away, shell goes further, cooling
• The elements that form are dependent on the original
mass of the star
• The rate that fusion occurs is dependent on the original
mass of the star
• The internal & external temperatures are dependent on
the original mass of the star
• What happens next is dependent on the original mass of
the star
Sun Size
• Shell keeps expanding until gravity can’t
hold on any longer
• Core keeps collapsing, fusion stops, still is
hot & glowing
• Core has become White Dwarf
• Continues to cool and dim
Planetary Nebula
• Note the remnant core (white dwarf)
surrounded by the expanding shell.
More massive
• Red Giant swells to supergiant
• If swells & contracts fast enough –
supernova explosion
• Remnant white dwarf will keep collapsing,
if there’s enough mass.
• Collapses to a Neutron Star
• Keeps collapsing if there’s enough mass
• Collapses to a Black Hole
Doppler Effect
• Shift away – Red shift
• Shift towards – blue shift
• Edwin Hubble – discovered most galaxies
are moving away from us.
• Universe is expanding, it must have been
much smaller
Big Bang Theory
• A superpowerful explosion of energy
and matter 15 billion years ago
• Just prior to BB all matter and
energy was concentrated into an
infinitesimally small ball
• After Big Bang, energy and matter
began to cool, gravity pulls matter
into particles, stars, galaxies begin to
form
• (H eventually formed)
• Planet –solar system – Milky Way – Local
Group - Universe
Galaxies
• Spiral
• Andromeda
• Ellipitcal
• Irregular
Motion
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Rotation of Earth on Axis
Earth orbits Sun
Sun orbits center of Milky Way Galaxies are also moving
Test format
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Multiple choice
Short answer
Long answer
paragraph
Diagram High vs low mass stars
• Neb – proto-MS-RG- PN - WD-BD
• Neb- proto-MS-RG-SG-SN-WD-NS –BH
– May stop at WD or NS or BH, depending on
the mass of the remnant core
• Diagram High vs low mass stars
• How far and what is the closest star (Sun
and other)
• Stellar evolution
• Compare life span of High and low mass
star
• What is a star
• Difference between a star and a planet –
stars produce light/planets reflect light
• In a star, what is needed to create a
neutron star?
• How do scientists use spectrums?
• What are absorption/ emission
spectrum?
• What do we need to start a star
forming?
– Dust, gas (matter) & energy (shock wave)
Warm up
• Why is it so hard to find Black Holes?