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
• 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
• Ellipitcal
• Irregular
Motion
• Rotation of Earth on Axis
• Earth orbits Sun
• Sun orbits center of Milky Way -
• Galaxies are also moving
Test format
• 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?