A star’s spectrum exhibits a Doppler shift if it is moving towards or away from us
Doppler shift: When a source of waves are approaching or receding, the observed wavelengths are changed.
Ex: A train rushing by, the pitch of the train’s whistle drops abruptly as it passes
Doppler Shift of Sound S = A moving source of sound such as a train whistle Observer 2 hears a higher pitch whistle, and the pitch drops suddenly when the source passes Observer 1 hears a lower pitch whistle than observe 2 For observer 2, the waves are pushed together
Absolute magnitude measures a star’s true brightness
Absolute magnitude is the magnitude that a star would have at a distance of 10 parsecs (32.6ly)
Sirius is the brightest star in our sky, which star, Sirius or Polaris, is truly the brightest? Star Polaris Sirius Apparent Magnitude +2.3 -1.5 Absolute Magnitude -4.6 +1.4 Distance 240 Parsecs 2.7 Parsecs