Properties of Stars

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Department
Astronomy & Astrophysics
Course
AST201H1
Professor
Michael Reid
Semester
Winter

Description
AST201H-­‐  Stars  and  Galaxies         Professor  Michael  Reid                                                                                                                            Lecture  Notes     February  5,  2013   Lecture  9:  Property  of  Stars   Luminosity  and  Apparent  Brightness   • Luminosity  –  the  amount  of  energy  something  produces  per  second     o Watt  –  amount  of  energy  per  second  (measuring  unit  for  luminosity)   o Describing  every  luminosity  of  the  star  in  terms  of  the  Sun’s   luminosity     • Luminosity  is  how  BRIGHT  something  is  intrinsically  which  is  different   from  the  term  brightness   § It  does  not  matter  whether  how  bright  it  appears  or  the   distance  of  the  star     § Fixed  property  regardless  of  what  the  observer  is  doing     • Apparent  brightness  –  how  bright  something  appears  to  you  –  distance   matters     Property  of  Stars   • Chemical  composition  –  the  wavelengths  at  the  which  its  spectrum  shows   absorption  lines   •   •   •   •   •   •   • Temperature  –  the  wavelength  at  which  its  blackbody  curve  peaks;  overall   colour                 AST201H-­‐  Stars  and  Galaxies         Professor  Michael  Reid                                                                                                                            Lecture  Notes                                       • Motion  along  line  of  sight  or  speed  –  the  Doppler  shift  of  its  spectral  lines     o Blueshift  or  redshift          
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