Word: cepheid
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Dates: during 1994-1994
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...know the rate of expansion. Formally known as the Hubble constant, this expansion factor is calculated by measuring the distance from our galaxy to other galaxies (something difficult to do) and determining how fast that distance is increasing (an easier task). Scientists look for particular kinds of stars, called Cepheid variables, because they know the inherent brightness of these stars. The fainter they appear here on earth, the farther away they are, and the distance can be roughly calculated. As researchers find Cepheids farther and farther away, calculations of the Hubble constant become more and more accurate...