Transcript The Hertzsprung – Russell Diagram

The Hertzsprung – Russell
Diagram
The HR diagram
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Developed by Einar Hertzsprung and
Henry Russell
Relationship between absolute mag.
and the temperature of stars
A star’s position on the diagram tells
about size, color, and temp.
Also is an evolutionary guide of a
star’s life
Positioning on the HR Diagram
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Main sequence stars
– Upper left corner to lower right corner
 90% of stars are located along the
main sequence
 Upper left – blue/blue-white, large
mass, bright, hot
 Lower right – red, small, dim, cool
 Sun is located in the middle of the
main sequence
Positioning (con’t)
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Red Giants and Super Giants
– Above and to the right of the main seq.
 Very bright, red in color, very large,
cool in temperature
 Brightness of stars are due to their
enormous size
Positioning (con’t)
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White Dwarfs
– Below the main seq. and centered
 Not actually white
 Very small (Earth size), dim, small
mass
Stellar Evolution and The HR
Diagram
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The position of a star indicates where
it is along its evolution
Sequence depends on star’s mass
2 types of evolutionary sequences
– Sun size and smaller
– 10x the Sun’s mass
Stellar Evol. and the HR diag.
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(con’t)
Sun sized star’s
1. Interstellar cloud
2. Protostar – nuclear fusion begins here
3. Main sequence – 90% of life time
4. Red Giant –large, cooler
5. Yellow Giant- often variable in brightness
6. 2nd Red Giant – larger than 1st red giant
7. White Dwarf
Stellar Evol. and the HR diag.
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(con’t)
10x the Sun’s Mass
1. Interstellar cloud
2. Protostar- nuclear fusion begins here
3. Massive Main Sequence Star- larger
and brighter than the Sun
4. Pulsating Yellow
5. Super Red Giant
6. Supernova – Explosion, new nebula
formed
7. Black hole or Neutron Star