Measuring Galaxy Distances

Science

How do astronomers know how far away a galaxy billions of light-years away really is? Discover the cosmic distance ladder — the brilliant chain of techniques that builds from measuring nearby stars to probing the farthest reaches of the observable universe.

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10
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5–10 min
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Q1 Question 1 of 10

What is the cosmic distance ladder?

Q2 Question 2 of 10

What is a Cepheid variable star, and why is it useful for measuring distances?

Q3 Question 3 of 10

What did Edwin Hubble prove in 1923-1924 using Cepheid variable stars?

Q4 Question 4 of 10

Who discovered the period-luminosity relationship for Cepheid variable stars?

Q5 Question 5 of 10

Why are Type Ia supernovae called standard candles?

Q6 Question 6 of 10

What is the Tully-Fisher relation?

Q7 Question 7 of 10

What does the Hubble constant H0 of approximately 70 km/s/Mpc mean?

Q8 Question 8 of 10

What is the Hubble tension?

Q9 Question 9 of 10

Why does redshift become a useful distance indicator for very distant galaxies?

Q10 Question 10 of 10

Who first measured the recession velocities of many galaxies before Hubble combined them with distances?