The standard candle method

If we know the intrinsic brightness of an object in space - that is, how bright an object really is - then we can estimate its distance from how bright it appears to us from Earth.

  • One type of standard candle is a 'Cepheid variable'. Cepheid variables are a type of star that has a consistent relationship between their intrinsic brightness and how fast they pulsate. (If it pulsates at x speed, you know its intrinsic brightness is y.)
  • Supernovae is another kind of standard candle and allows astronomers to calculate to the standard candle's home galaxy.



How do we calculate distances to other galaxies?

The 'Hubble-Lemaître' law is more useful for calculating distant galaxies. The law shows that the further the galaxy is from Earth, the faster it moves away from us - the consequence of the Universe expanding.

The galaxy's speed is measured by analysing the shift in the galaxy's light towards the red end of its light spectrum. Once the speed is known, astronomers can work out its distance.


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