.A CEPHEID DISTANCE TO THE FORNAX CLUSTER AND THE LOCAL EXPANSION RATE OF THE UNIVERSE

The Hubble Space Telescope is being used to measure accurate Cepheid distances to nearby galaxies with the ultimate aim of determining the Hubble constant, Ho. For the first time, it has become feasible to use Cepheid variables to derive a distance to a galaxy in the southern hemisphere cluster of Fornax. Based on the discovery of 37 Cepheids in the Fornax galaxy NGC 1365, a distance to this galaxy of 18.6A0.6 Mpc (statistical error only) is obtained. This distance leads to a value of Ho = 70+ 7(random) +18(systematic) km/sec/Mpc in good agreement with estimates of the Hubble constant further afield. The determination of an accurate value of the Hubble constant requires the measurement of accurate galaxy distances and velocities. Both the Virgo and Fornax clusters of galaxies are close enough to be studied in considerable detail; on the other hand, they are sufficiently distant that the bulk of their measure