Chapter 30.1: Characteristics of Stars

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Chapter 30.1 Characteristics of Stars

• Star ball of gas that gives off a tremendous
  amount of energy in the form of heat and light.
• Our own Sun is considered an average star!

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Characteristics

1. Starlight- light given off by stars.
2. Composition- what elements make up the stars.
3. Temperature- how hot how cold?
4. Size Mass- how big how small?
5. Motion- actual motion vs. apparent.
6. Distance- how close how far away?
7. Brightness- apparent vs. absolute magnitude.

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Starlight

• -by analyzing the light stars emit, we can
  determine the stars composition (elements
  present) and temperature.

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Composition

• -Star composition is determined by analyzing the
  light being emitted. Equipment is called a
  spectrometer.
• -Since different elements absorb different
  wavelengths of light, elements can be determined.
• -Stars are made up of gas elements. (Hydrogen is
  the most common!)

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Temperature

• -temperature is determined by the stars color.
• -temp.s range from
• 2,800 to 50,000 oC.

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Size Mass

• -Some dwarf stars are as small
• as the Earth.
• -Our sun is a medium size star (1,390,000 km).
• -Some stars are 1,000 times larger than our sun.
• -Density affects massno relationship between
  size and mass.
• Example a star can be smaller than our sun,
  but have a greater massmeaning it is more dense!

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Motion

• 1. Actual motion- what we see with telescopes.
• 2. Apparent motion- This is motion visible to the
  unaided eye in a dark sky due to movement of
  Earth.
• Stars have three actual motions
• 1. rotate
• 2. revolve
• 3. move toward (blue shift) or away (red
  shift)
• from Earth

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Distance

• -Light Year 9.5x1012km Distance that light
  travels in one year.
• Example light from the sun takes 8 mins.
• to reach the Earth
• -Astronomical Unit (AU) - A unit of length used
  to measure distances in solar system.
• Example Sun to Earth 1 A.U.

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Brightness a.ka. Stellar Magnitude

• -Absolute Magnitude true brightness
• -Apparent Magnitude brightness of a star as it
• appears to us on Earth.
• Brightest stars have lowest numbers.
• (negative s)
• Dimmest stars have highest numbers.
• (positive s)