Stars, Galaxies, and the Universe

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Stars, Galaxies, and theUniverse

• Chapter 21.1 21.2

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Telescopes

• Electromagnetic Radiation
• - energy that can travel through space
• in the form of waves
• Electromagnetic Spectrum
• - the entire range of radiation

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Telescopes

• Telescopes are instruments that collect and focus
  light and other forms of electromagnetic
  radiation.
• Telescopes make distant objects appear larger and
  brighter

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Telescopes

• 3 kinds of telescopes
• - Optical telescopes
• 1) Refracting telescopes
• use convex lenses

The larger the lens, the stronger the telescope
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Largest Refracting Telescope

• The Great Paris Exhibition Telescope of 1900
• 1.25 m diameter

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Telescopes

• 2) Reflecting Telescopes
• - use concave mirrors

The larger the mirror, the stronger the telescope
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Largest Reflecting Telescope

• Large Binocular Telescope
• Mount Graham International Observatory, Arizona
• Two 8.4 m diameter
• Subaru Telescope
• Hawaii
• 8.2 m diameter

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Telescopes

• - Radio Telescopes devices used to detect
  radio waves from objects in space

The larger the dish, the stronger the telescope
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Telescopes

• Largest radio telescopes
• Arecibo, Puerto Rico
• 1,001 ft

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Telescopes

• Observatory a building that contains one or
  more telescopes
• Usually located on mountain tops or in space

Hubble space telescope is a reflecting (optical)
telescope
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• why do we study the stars?

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Characteristics of Stars

• Constellations
• imaginary patterns
• of stars in the sky

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Classifying Stars

• Stars are classified using color and temperature

Hottest
Coldest
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Classifying Stars

• Stars are classified using size

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Classifying Stars

• Stars are classified according to composition

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Brightness of Stars

• The brightness of a star depends on both its size
  and temperature
• A large star may look bright, even though it is
  relatively cool, because of its size
• A small star may look bright because it is hot

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Brightness of Stars

• Apparent Brightness- how bright a star appears
  from Earth

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Brightness of Stars

• Absolute Brightness- how bright a star would be
  at a standard distance

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Measuring Distances to Stars

• Light-year distance light travels in a year
• - used to express distance
• between stars
• -speed of light 300,000 km/s

1 light-year is about 9.5 million million
kilometers
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• how to measure extreme distances

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Measuring Distances to Stars

• Parallax the apparent change in position of an
  object when you look at it from different places

Parallax can be used to measure stars
that are only a few hundred light-years
away
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• What is Parallax? - YouTube

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Hertzsprung-Russell Diagram

• Plotting of stars on a graph based on temperature
  and absolute brightness
• Used to understand how stars change over time

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