281 A Closer Look at Light

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28-1 A Closer Look at Light

• A.   What is Light?
• a. Light-A form of Electromagnetic Radiation,
  which is energy that travels in waves.
• b. List some examples of electromagnetic
  radiation
• c. How do they travel?
• How fast?
• d. What is the electromagnetic spectrum? See pg.
  613.

As a wave
300,000 km/s or 186,300 mph
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28-1 A Closer Look at Light

• B.   The Spectroscope
• a. Visible white light is made up various colors
  of different wavelengths.
• b. These are the colors of the rainbow. ROYGBIV
• c. What does a spectroscope do?

It separates white light into its various
wavelengths.
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28-1 A Closer Look at Light

• C.   Types of Visible Spectra
• a.   Three types of Spectra
•           i.  Continuous-is an unbroken band of
  colors, which shows that its source is emitting
  light of all visible wavelengths.
•           ii.  Emission-a series of unevenly
  spaced lines of different colors and brightness.
•              

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28-1 A Closer Look at Light

•            iii.  Absorption-a continuous spectrum
  crossed by dark lines.
• b.  A stars absorption spectrum indicates its
  composition.
•  

• www.classzone.com/books/earth_science/terc/content
  /visualizations/es2801/es2801page01.cfm?chapter_no
  28

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28-1 A Closer Look at Light

• D.   The Doppler Effect
• a. What is the Doppler effect?
• b. What causes this?
• c. It can indicate the direction of a stars
  movement.

The compression and stretching of waves
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28-1 A Closer Look at Light

• d. A star moving towards the earth creates a
  shorter wavelength (blue in color).
• e. A star moving away from the earth creates a
  longer wavelength (red shift).

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28-2 Stars and Their Characteristics

• A.   Early Observations
• a.   There are billions of stars in the sky.
  How far away is the closest star?
• b.   Constellations-Groupings of stars. Usually
  have ancient names. Human inventions. There are
  88 constellations in the night sky.
• c.    What are some examples?
• d.    What causes the motion of constellations
  in the night sky?
•  

Four light years
Big Dipper, Orion, Gemini.
Rotation of the Earth
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28-2 Stars and Their Characteristics

•  
• B.   Apparent Magnitude
• a.   It is the measure of how bright a star
  appears to be in the night sky.
• b.   The lower the magnitude number, the
  brighter the star is.
• c.   A first magnitude star is 100 times
  brighter than a sixth magnitude star.

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28-2 Stars and Their Characteristics

• C.   Distances to Stars
• a.   How far is an astronomical unit?
• b.   Light year-Distance a light wave travels in
  one year or 9.5 trillion km.
• c.   What is parallax? Draw diagram on page
  620.
• d. Parsec-Equal to 3.258 light years or
  3.086x1013
•  

150,000,000 km or the distance from the earth to
the sun
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28-2 Stars and Their Characteristics

• D.   Elements in Stars
• a.   A star is 69 Hydrogen and 29Helium.
  Heavier elements makes up the remaining 2.
• b.    Each star has a unique fingerprint. Why?

Because it is made up of different combinations
of gases and elements
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28-2 Stars and Their Characteristics

• E.   Mass, Size, and Temperature of Stars
• a.   Mass can only be inferred. What are some
  factors that can help to determine mass?
• b.   Stars come in a wide variety of sizes.
  Some are smaller than the earth and others are
  200 times larger than the sun.

Composition and Gravitational Influence
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28-2 Stars and Their Characteristics

• c.    Density also varies. One star near Sirius
  is so dense that one-teaspoon would weigh over a
  ton on earth.
• d.    Temperature and Color of Stars-A stars
  color varies depending on its surface
  temperature. See page 622.

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28-2 Stars and Their Characteristics

• F.   Luminosity and Absolute Magnitude
• a.   Luminosity-the actual brightness.
• b.   Apparent Magnitude-How the star actually
  appears.
• c.   Absolute Magnitude-a measure of how bright
  the star would be if all stars were at the same
  distance.

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28-2 Stars and Their Characteristics

• d.   Variable Stars-Show a regular variation of
  brightness over cycles.
• e.   Cephied Variables- Pulsating supergiants
  that have 5 day cycles (most of them).
• f. Eclipsing Binary-One star eclipses another.

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28-3 Life Cycles of Stars

• 1. Hertzsprung-Russell Diagram
• a.   Why are stars like people?
• b.  The more massive they are, the shorter
  there life will be.
• c.   Plots luminosity of stars against their
  surface
• temperature.
• d.  Where do 90 of all stars fall?

They come in different shapes, sizes, colors
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28-3 Life Cycles of Stars

• e.   They fuse hydrogen into helium.
• f.     Giant Stars-High luminosity, 10-100
  times bigger than the sun.
• g.  Super Giants-more than 100x bigger than the
  sun. High temperature, high luminosity.
• h.  White Dwarfs-Near the end of their life
  cycle. Once were red giants, now they are just
  the glowing core.

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28-3 Life Cycles of Stars

• 2. Birth of a Star
• a.   Nebula-Cloud of gas and dust that stars
  form from. What is it made up of?
• b.  What has to happen for fusion to begin?

99 Hydrogen 1 dust
Shock Wave GravityFriction increase in
Temperature
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28-3 Life Cycles of Stars

• 3. Death of a Star Like the Sun Massive Stars
• When does a star start to die?
• b. What creates a planetary nebula?
• See diagram on page 628-29.
• c. What does the explosion of a supernova
  produce?

When it runs out of Hydrogen
The blown off gases
Neutron Star or a Black hole
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28-4 Galaxies and the Universe

• Remnants of Massive Stars
• Neutron Star- 20 km in diameter, trillions of
  times more dense than the sun.
• Pulsar-Rapidly spinning neutron star that emits
  pulses of radiation.
• Black hole- Incredibly dense remnant of a star.
  Gravitational force is so strong that light
  cannot escape.
• What are Galaxies?

Systems containing billions of stars
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28-4 Galaxies and the Universe

• How old is the Universe?
• b. Galaxies-systems containing millions or even
  billions of stars. It is estimated that there
  are between 50 and 100 billion galaxies.
• Which galaxy do we belong to?
• d. What are the dimensions of our galaxy?

10-20 billion years
Milky Way
100,000 light years by 10,000 light years
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28-4 Galaxies and the Universe

• 5. Types of Galaxies
• Spiral Galaxies- Pinwheel in shape.
• b. Elliptical-Lens shaped with stars clustered
  around the center.
• c. Irregular-random arrangement of stars.
• d. Quasars-Extremely distant objects. Very
  luminous.
•  

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28-4 Galaxies and the Universe

• 6. Origin of the Universe
• What does the Big Bang Model Say?
• b. Evidence support the model is the universes
  expansion.
• c. What other supporting evidence is there?

The universe starting from a central microscopic
point
Redshifts