HertzsprungRussell Diagrams Astronomy An HR Diagram Based on
Hertzsprung-Russell Diagrams Astronomy
An H-R Diagram Based on Hipparcos Data
A Modern Version of the H-R Diagram
• GENERAL INFO: • Plot of luminosity vs. temp or by absolute magnitude vs. spectral class • 90% of stars are in a band called the main sequence (our sun is in middle) • Other 10% are in upper right and lower left
• Blue giants- • upper left part of main sequence • BIG, luminous, hot • Examples: Rigel
• Red dwarfs- • lower right portion of main sequence • little, faint, cool • Examples: Barnard’s star
• White dwarfs- • lower left group OFF of the main sequence • little, faint, hot • Examples: Sirius B
• Red Giants- • upper right portion OFF the main sequence • big, luminous, cool • Examples: Arcturus, Aldeberan
• Red Supergiants- • same as red giants, just bigger • Examples: Betelgeuse, Antares
The Mass-Luminosity Relation for Main Sequence Stars
• A star’s position on the main sequence is determined by its MASS. • Most massive stars are most luminous • largest mass of a stable star is ~100 x sun • faintest red dwarfs are 1/10 sun’s mass • brown dwarf: too small to be a star (almost like Jupiter)
Most stars are… a) Red giants b) White dwarfs c) Red dwarfs d) Blue giants e) Main sequence stars
E • Blue giants? • Red giants? • White dwarfs? • The sun? • Red dwarfs?
E • Blue giants are… • Hot or cool? • Big or small? • Bright or faint?
E • Red giants are… • Hot or cool? • Big or small? • Bright or faint?
E • White dwarfs are… • Hot or cool? • Big or small? • Bright or faint?
E • Our sun is… • Hot or cool? • Big or small? • Bright or faint?
E • Red dwarfs are… • Hot or cool? • Big or small? • Bright or faint?
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