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Stars Characteristics

Stars Characteristics. What are the characteristics of a star?. Stars differ in… Mass Size Temperature Color Luminosity. Mass and Composition. A star is a massive ball of glowing gases, mainly hydrogen and helium.

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Stars Characteristics

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  1. Stars Characteristics

  2. What are the characteristics of a star? Stars differ in… • Mass • Size • Temperature • Color • Luminosity

  3. Mass and Composition • A star is a massive ball of glowing gases, mainly hydrogen and helium. • Bigger stars have more mass, greater gravity and are hotter than smaller stars.

  4. Star Size • Large Stars: Giants or Super Giants • Medium Stars: Main Sequence (the Sun) • Small Stars: White Dwarf or Neutron

  5. Star Energy • The enormous pressure and heat in a star’s core converts matter into energy. • This reaction is called nuclearfusion • In nuclear fusion, hydrogen atoms fuse to form helium atoms. • During each step of the process, mass is lost and energy is released.

  6. Star Energy cont. • The energy released causes the star (Sun) to shine and gives the star its high temperature.

  7. Star Temperature • Stars in the sky show tinges of different colors which reveal the stars’ temperatures. • Blue: hottest • Yellow: medium temperature • Red: coolest

  8. Classification of Stars

  9. Star Luminosity/Brightness • The brightness of a star depends upon the distance and its luminosity. • Apparent Brightness/Magnitude: a star’s brightness as seen from Earth. • Absolute Brightness/Luminosity: the actual brightness of the star.

  10. Stop and Think If person A has a pen flashlight and person B has a mega flashlight and both were standing at the front of the classroom, which light would appear brighter? If person A (pen light) stood in the classroom and person B (mega light) stood at the baseball fields across the street, which light would appear brighter? You cannot tell by looking in the sky how bright a star truly is. The farther away the star is, the less bright it will appear.

  11. The Hertzsprung-Russell Diagram • An H-R diagram plots stars according to their luminosity and temperature.

  12. Location of Stars on an H-R Diagram The main sequence is a major grouping of stars in the H-R Diagram

  13. Star MassPosition on H-R depends on mass • The larger the amount of mass in a star, the more luminous it is. • Giants: more mass, more luminous • Dwarfs: less mass, less luminous • During its lifetime a star will evolve on the H-R diagram depending on its mass.

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