Absolute Magnitude

• What does absolute magnitude measure in a star?

  The inherent brightness of a star
• What factors affect the apparent brightness of a star?

  Its luminosity and distance from Earth

  
• What does it mean if two stars have the same apparent magnitude?

  They may not emit the same light
• Why is absolute magnitude useful?

  It allows comparison at the same distance
• How is absolute magnitude defined?

  Brightness at 10 parsecs from Earth

  
• How do most stars appear at 10 parsecs?

  They appear brighter than from Earth
• What is the relationship between apparent and absolute magnitudes?

  They are measured on the same logarithmic scale
• How do absolute magnitudes compare to apparent magnitudes?

  Absolute magnitudes are often more negative
• What is the formula relating apparent magnitude, absolute magnitude, and distance?

  m − M = 5 log(d/10)

  
• What does the distance modulus represent?

  The difference between apparent and absolute magnitude
• What does a negative distance modulus indicate?

  The star is closer than 10 parsecs

  
• What does a positive distance modulus indicate?

  The star is further than 10 parsecs

  
• How do you determine the brightest star on the absolute magnitude scale from a table?

  • Compare apparent magnitudes
  • Identify the furthest star
  • The furthest star is the brightest

  
• How do you determine the dimmest star on the absolute magnitude scale from a table?

  • Compare apparent magnitudes
  • Identify the closest star
  • The closest star is the dimmest

  
• How do you convert light-years to parsecs?

  Divide by 3.26
• What is the absolute magnitude of Algenib?

  $-2.55$
• What are the examiner tips for comparing magnitudes?

  • Use specific language: 'brighter' or 'dimmer'
  • Avoid terms like 'bigger' or 'smaller'
  • Be comfortable with logarithmic calculations
• What is the conversion factor from parsecs to light-years?

  1 parsec = 3.26 light-years
• Why is it important to specify 'brighter' or 'dimmer' when discussing magnitudes?

  To avoid confusion in interpretation
• How does the distance of a star affect its apparent magnitude?

  Further stars appear dimmer than closer stars