Science 9: Unit E: Space Exploration

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Science 9 Unit E Space Exploration

• Topic 5 What Channel is That?

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Electromagnetic Radiation

• Light is one kind of electromagnetic radiation
  (EMR). Stars and other celestial objects give off
  all kinds of EMR the Sun sends out infrared
  radiation which warms the Earth, UV radiation
  which tans/burns our skin, and radio waves which
  we detect as static on our radios.

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History of Radio Astronomy

• Radio astronomy is the studying of radio waves
  given off by these celestial objects in order to
  learn more about them.
• In the 1930s telephone engineers noticed that
  there was a constant source of background radio
  radiation which interfered with their equipment.
  Karl Jansky built a radio antenna to study these
  signals and concluded that the signals came from
  outer space.
• Grote Reber, using a radio dish, discovered that
  certain areas in the sky gave off especially
  strong radio signals. Reber noted that the
  strongest radio signal came from the Sun,
  followed by Jupiter. He also noticed that outside
  the solar system, the strongest signal came from
  the center of the Milky Way Galaxy, full of
  stars. Objects that gave off especially strong
  signals were called Radio Objects.

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Radio Astronomy Contd

• Using radio waves to study celestial objects has
  one major disadvantage They dont produce as
  much detail as light. Our eyes cannot see radio
  waves so we lose information. A major advantage
  is that radio waves can travel farther because
  theyre larger and pass through dust clouds while
  light waves cannot.
• Computers now produce images showing the strength
  of radio signals weak signals are bluish while
  stronger signals get redder and finally white.

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Interferometry and the VLA

• Interferometry The use of many telescopes
  combined together so that the many radio signals
  could be combined by computer to produce a much
  more detailed single signal. The biggest example
  of radio interferometry is the Very Large Array
  (VLA) in New Mexico. This array has been used to
  study radio signals from alien sources. So far no
  luck.

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Very Long Baseline Interferometry (VLBI)

• Very Long Baseline Interferometry (VLBI) A much
  larger and newer example of interferometry that
  relies on radio telescopes connected wirelessly
  over a much larger distance, even the entire
  planet.