Three Steps to the Hubble Constant (IMAGE)

Johns Hopkins University

Three Steps to the Hubble Constant

Caption

This illustration shows the three basic steps astronomers use to calculate how fast the universe expands over time, a value called the Hubble constant. All the steps involve building a strong "cosmic distance ladder," by starting with measuring accurate distances to nearby galaxies and then moving to galaxies farther and farther away. This "ladder" is a series of measurements of different kinds of astronomical objects with an intrinsic brightness that researchers can use to calculate distances.

Credit

NASA, ESA, and A. Feild (STScI)

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