• Astronomers measure the brightness of stars at a standard distance using the?absolute?magnitude scale
• This is because a really bright star far away will look the same as a dim star nearby, so it is difficult to measure the brightness directly
• This scale runs back to front:
  • The?brighter?the star, the?smaller?the magnitude
  • The?dimmer?the star, the?larger?the magnitude

   

• The brightness of a star depends on two main factors:
  • How much light the star emits
  • How far away the star is (more distant stars are usually fainter than nearby stars)

   

Examples of the apparent magnitude of different bodies in the Solar System

• The absolute magnitude of stars is a measure of?how bright?they would be if they were all the?same distance?away from Earth
  • More specifically, if it was 10 parsecs (32.6 light-years or 3.04 × 10¹⁴?km) away from the Earth

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