13: Characteristics of Stars

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1-3 Characteristics of Stars
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I. Five Sizes of Stars

• A. Neutron Stars Algol
• B. White Dwarfs Van Maanens star, Sirius,
  Vega
• C. Medium-Sized Sun, Sirius, Alpha Centauri A
• D. Giant Stars Aldebaran, Alpha Centauri B
• E. Supergiants Rigel, Betelgeuse, Proxima
  Centauri

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II. Composition of Stars

• Astronomers use a spectroscope
• 1. Elements produce a characteristic set of
  colors when passed through a spectroscope
  (spectral fingerprints).

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Composition of Stars (cont.)

• Almost all stars have the same composition.
• 1. Hydrogen and Helium
• a. 96 to 99 of stars
• 2. Neon, Oxygen, Carbon, Nitrogen

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III. Surface Temperature of Stars

• Blue 35,000 ºC (Algol)
• White 10,000 ºC (Sirius)
• Yellow 6,000 ºC (Sun) (A.C.A)
• Red-Orange 5,000 ºC (A.C.B)
• Red 3,000 ºC (Proxima Centauri)

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IV. Brightness of a Star

• Depends on size, surface temperature, and
  distance from Earth
• 1. Apparent magnitude Brightness of a
• star as it appears from Earth
• 2. Absolute magnitude Amount of light
• a star actually gives off
• 3. Cepheid Pulsating star

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V. H-R Diagram

• Shows the relationship between absolute
• magnitude and surface temperature

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VI. Measuring Star Distance

• Parallax Method a method used to measure
• the distance to stars.

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VII. Why Stars Shine

• Nuclear Fusion Hydrogen atoms are fused to form
  helium atoms.
• 1. Releases heat and light
• a. X-ray, ultraviolet, infrared,
  visible