Insert: Beyond our Solar System

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Insert Beyond our Solar System
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Deployment of the Hubble Space Telescope in Earth
orbit, April 24, 1990
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The 300-meter radio telescope at Arecibo, Puerto
Rico
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Hertzsprung-Russell diagram

• Shows the relation between stellar
• Brightness (absolute magnitude) and
• Temperature
• Diagram is made by plotting (graphing) each
  star's
• Luminosity (brightness) and
• Temperature

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Hertzsprung-Russell diagram

• Parts of an H-R diagram
• Main-sequence stars
• 90 of all stars
• Band through the center of the H-R diagram
• Sun is in the main-sequence
• Giants (or red giants)
• Very luminous
• Large
• Very large giants are called supergiants
• Only a few percent of all stars

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Hertzsprung-Russell diagram

• Parts of an H-R diagram
• White dwarfs
• Fainter than main-sequence stars
• Small (approximate the size of Earth)
• Lower-central area on the H-R diagram
• Not all are white in color
• Perhaps 10 of all stars

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Hertzsprung-Russell diagram
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The Orion Nebula is a well-known emission nebula
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A faint blue reflection nebula in the Pleiades
star cluster
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Stellar evolution

• Two opposing forces in a star are
• Gravity contracts
• Thermal nuclear energy expands
• Stages
• Birth
• Main-sequence stage
• 90 of a star's life is in the main-sequence
• Red giant stage
• Burnout and death
• white dwarf, neutron star, or a black hole

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Evolutionary stages
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Stellar evolution
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Stellar remnants

• White dwarf
• Small and Dense
• Spoonful weighs several tons
• Neutron star
• Gravitational force collapses atoms
• Electrons combine with protons to produce
  neutrons
• Pea size sample weighs 100 million tons
• First one discovered in early 1970s Crab nebula
  (remnant of an A.D. 1054 supernova)

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Crab Nebula in the constellation Taurus
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Stellar remnants

• Black hole
• More dense than a neutron star
• Intense surface gravity lets no light escape
• As matter is pulled into it
• Becomes very hot
• Emits x-rays
• Likely candidate is Cygnus X-1, a strong x-ray
  source

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Binary Pair with a Red Giant and a Black Hole
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Galaxies

• Other galaxies
• Existence was first proposed in mid-1700s by
  Immanuel Kant
• Four basic types of galaxies
• Spiral galaxy
• Arms extending from nucleus
• About 30 of all galaxies
• e.g., Milky Way

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Face-on view of the Milk Way Galaxy
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Edge-on view of the Milk Way Galaxy
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Great Galaxy, a spiral galaxy, in the
constellation Andromeda
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Galaxies

• Other galaxies
• Four basic types of galaxies
• Barred spiral galaxy
• Elliptical galaxy
• Irregular galaxy

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The study of light

• Doppler effect
• The apparent change in wavelength of radiation
  caused by the relative motions of the source and
  observer
• Used to determine
• Direction of motion
• Increasing distance wavelength is longer
  ("stretches")
• Decreasing distance makes wavelength shorter
  ("compresses")

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The Doppler effect
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Red shifts

• Doppler effect
• Change in the wavelength of light emitted by an
  object due to its motion
• Movement away stretches the wavelength
• Light appears redder
• Movement toward squeezes the wavelength
• Light shifted toward the blue
• Expanding universe
• Most galaxies exhibit a red Doppler shift

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Raisin bread analogy of an expanding universe
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Big Bang theory

• Accounts for galaxies moving away from us
• Universe was once confined to a "ball" that was
• Supermassive
• Dense
• Hot

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Big Bang theory

• Big Bang marks the inception of the universe
• Occurred about 15 billion years ago
• All matter and space was created
• Matter is moving outward
• Fate of the universe
• Two possibilities
• Universe will last forever
• Outward expansion sill stop and gravitational
  contraction will follow

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Big Bang theory

• Fate of the universe
• Final fate depends on the average density of the
  universe
• If the density is more than the critical density,
  then the universe would contract
• Current estimates point to less then the critical
  density and predict an ever-expanding, or open,
  universe

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End of Chapter 16