Astronomy Stars 09
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Astronomy Stars 09

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A Power Point done by Kristen Hannan and myself for an 8th Grade unti on astronomy

A Power Point done by Kristen Hannan and myself for an 8th Grade unti on astronomy

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Astronomy Stars 09 Astronomy Stars 09 Presentation Transcript

  • Astronomy Stars
  • What is a Star?
    • A large mass of gases
    • Most stars produce energy by nuclear fusion (converting Hydrogen to Helium)
  • Star Color
    • The spectrum (wavelengths of light produced by a star) is analyzed and the star is given a letter designation based on color and temperature
  • Star Color Range
    • O B A F G K M
    • Hotter---------------------------------------Cooler
    • Blue-White(OBAF) Yellow (G) Red(KM)
    • There are 10 divisions between spectral classes (each letter) 0-9 (ex: G0,G1,G2…….G9)
    • Our sun is a G2 star
  • Luminosity
    • =The actual brightness of a star
    • Depends on size and temperature
    • Distance from Earth is NOT a factor
    • Examples:
    • if 2 stars have the same temp, the larger star would be more luminous
    • If 2 stars were the same size but had different temps, the hotter star would be more luminous
  • Apparent Magnitude
    • = how bright a star appears to an observer on Earth
    • Depends on luminosity and distance
    • Brightest stars are 1 st magnitude; faintest stars (seen with naked eye) are 6 th magnitude
  • Absolute Magnitude
    • =the apparent magnitude of a star placed 32.6 light years from the sun
    • Astronomers use to compare brightness of different stars since all stars are different distances from Earth
    • Ex: Sun= 4.8 abs.mag (average star)
    • Rigel= -6.75 abs mag (very bright star)
  • Hertzsprung Russell Diagram (H-R Diagram)
    • A graph in which a star’s temperature is plotted against its absolute magnitude
    • Used to determine information about a star’s properties and life cycle
    • * see book p 626
  •  
  • Red Giants
    • Large, red stars that are cooler and more luminous than blue-white stars.
  • Supergiants
    • Large, low-density stars that are hundreds of times more luminous than red giants
    • *The largest of all stars
    • Ex: Betelgeuse (in Orion)
  • Dwarf Stars
    • Stars of absolute magnitude +1 or less
    • Most are red, yellow, blue (some white)
    • High density, hot, dim
  • Nebula
    • = A cloud of gas and dust where a star begins its life
  • Supernova
    • =The explosion of a large star
    • Millions of times brighter than the original star’s brightness