Distance to the Virgo cluster galaxy M100 from Hubble Space Telescope observations of Cepheids

Accurate distances to galaxies are critical for determining the present expansion rate of the Universe or Hubble constant (H₀). An important step in resolving the current uncertainty in H₀ is the measurement of the distance to the Virgo cluster of galaxies. New observations using the Hubble Space Telescope yield a distance of 17.1 +/- 1.8 Mpc to the Virgo cluster galaxy M100. This distance leads to a value of H₀ = 80 +/- 17 km s^-1 Mpc^-1. A comparable value of H₀ is also derived from the Coma cluster using independent estimates of its distance ratio relative to the Virgo cluster.