The Stars

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The Stars

• Chapter 14

Great Idea The Sun and other stars use nuclear
fusion reactions to convert mass into energy.
Eventually, when a stars nuclear fuel is
depleted, the star must burn out.
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Chapter Outline

• The Nature of Stars
• The Anatomy of Stars
• The Variety of Stars
• The Life Cycles of Stars

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The Nature of Stars
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The Nature of Stars

• Astronomy
• Oldest science
• Star
• Fusion reactor in space
• Ball of gas
• All stars have a beginning and an ending

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Measuring the Stars with Telescopes and Satellites

• Electromagnetic radiation
• Measurement of photons
• Wavelength
• Intensity
• Direction
• Variation

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Telescopes
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Orbiting Observatories

• Great Observatories Program
• Hubble Space Telescope
• Spitzer Infrared Telescope
• Chandra X-Ray Observatory

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The Anatomy of Stars
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The Structure of the Sun

• Structure
• Stellar core
• Convection zone
• Photosphere
• Chromosphere
• Corona
• Solar Wind
• Stream of particles

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The Suns Energy Source Fusion

• Suns Energy Source
• Historical
• Current
• hydrogen
• Fusion
• 3-steps-hydrogen burning
• P P ? D e neutrino energy
• D P ? 3He photon energy
• 3He 3He? 4He 2protons photon energy
• Life expectancy
• 11 billion years

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The Variety of Stars

• Differences
• Color
• Brightness
• Distance
• Absolute brightness
• Energy output
• luminosity
• Apparent brightness
• Behavior
• Total mass
• age

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The Astronomical Distance Scale

• Time
• Light-years
• Measurement
• Triangulation
• Cepheid variable

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The Hertzsprung-Russel Diagram

• Star Groupings
• Main-sequence stars
• Red giants
• White dwarfs

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The Life Cycles of Stars
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The Birth of Stars

• Nebular Hypothesis
• Laplace

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The Main Sequence and the Death of Stars

• Stars much less massive than the sun
• Brown dwarf
• Glows 100 billion years
• No change in size, temperature, energy output

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The Main Sequence and the Death of Stars

• Stars about the mass of the sun
• Hydrogen burning at faster rate
• Move off main sequence
• Helium burning
• Red giant
• Begin collapse
• White dwarf

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The Main Sequence and the Death of Stars

• Very Large Stars
• Successive collapses and burnings
• Iron core
• Catastrophic collapse
• supernova

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Neutron Stars and Pulsars

• Neutron Star
• Dense and small
• High rotation rate
• Little light
• Pulsar
• Special neutron star
• Electromagnetic radiation
• End state of supernova

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Black Holes

• Black Hole
• Result of collapse large star
• Nothing escapes from surface
• Cannot see them
• See impact on other stars
• Detect x-rays, gamma rays