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Hertzsprung-Russell Diagram
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Star Classification Stars can be classified in three ways:
1. Size – How massive the star is 2. Temperature – A stars color reveals its temperature. Red stars have a cooler temperature, and blue stars have a warmer temperature. 3. Brightness/Magnitude – The amount of light a star gives off depends on its size and temperature.
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H-R Diagram Compares the temperature, color and luminosity (brightness) of stars on a graph. The temperature is the surface temperature of the star The brightness of the star is its absolute magnitude
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APPARENT MAGNITUDE VS. ABSOLUTE MAGNITUDE
Measure of the amount of a star’s light received on Earth Apparent magnitude Measure of the amount of light a star actually gives off Absolute magnitude
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Color indicates temperature
STAR PROPERTIES Color indicates temperature Hot stars are Blue Cool stars are Red Medium temperature stars are Yellow
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Explaining the H-R Diagram
Temperature: horizontal (bottom) axis. hotter at left cooler toward right
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Explaining the H-R Diagram
Brightness: vertical (left side) axis. brightest stars near top dim stars near bottom
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Explaining the H-R Diagram
A star’s position on the diagram will change as it moves from its “birth” to its “death”.
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leftover centers of old stars
White dwarfs small, hot stars leftover centers of old stars
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Red-Giants When star runs out of energy, the center shrinks and the outer part expands outward. It will grow very large and cool.
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Supergiants Very massive cool giant star
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Main Sequence Stretches diagonal from the top left to the right bottom Our sun is an average main sequence star
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Blue Supergiants Very massive blue stars Quickly use up energy and turn into Giants or Supergiants
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Red Dwarfs Low-mass stars Oldest stars in galaxy
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Explaining the H-R Diagram
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