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Cepheids are the pillar of the extragalactic distance scale, but their reach in distance is not sufficient to calibrate H_0. Yet HST has provided Cepheid distances to eight galaxies which have produced SNe Ia. The latter are used as nearly perfect standard candles to carry the distance scale to 30,000 km/s, giving H_0 = 58 +/- 5. This determination finds support in other methods but its range in distance and its weight is unparalleled.

生成讲解博客的中文版本

生成AI智能校验的中文版本