THE UNIVERSE

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THE UNIVERSE
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Distant Stars

• Our closest neighbor
• Proxima Centauri
• Distance 4.3 lightyears

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Properties of the Stars

• Star observation involves collecting and
  analyzing radiation coming from the stars
• Measurable properties
• Distance
• Brightness
• Color
• Temperature
• Mass

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Stellar Distance

• Indirect measurement stellar parallax

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Stellar Brightness Magnitude (m)

• Apparent magnitude
• Size
• Temperature
• Distance
• Hipparchus m1 m6
• Smaller magnitudes are brighter
• Magnitude is a logarithmic scale
• ?m 5 ? 1 100
• ?m 1 ? 1 2.5

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Stellar Brightness Magnitude (m)

• Absolute magnitude
• Calculated at a standard distance of 32.6 ly

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Hertzsprung-Russel Diagram

• Relationship between true brightness and
  temperature of stars
• 90 main sequence stars
• The hottest stars are the brightest
• Luminosity related to brightness

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Stellar Evolution

• Star birth
• Dark, cool interstellar clouds
• Gaseous clouds
• 92 hydrogen
• 7 helium
• lt 1 heavier elements

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The End
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• Galaxies
• http//hubblesite.org/explore_astronomy/cosmic_col
  lision/
• Black Holes
• hubblesite.org/explore_astronomy/black_holes/
• Telescopes
• hubblesite.org/explore_astronomy/piercing_the_sky/