Skip to Main Content  Lifting the veil on Hubble's Constant  Pin
it  Lifting the Veil on Hubble's Constant  Today's HST
measurements shed new light on the history and fate of the
Cosmos  with apologies to King LearMay 25, 1999: In Julius
Caesar William Shakespeare wrote "But I am constant as the
Northern Star, of whose true and resting quality there is no
fellow in the firmament." However, had he known about cosmology,
he'd have probably chosen a better comparison than Polaris,
which is actually a variable star.  Stars like Polaris, called
Cepheid variables, have a wonderful property (wonderful to
astronomers, that is). The rate at which they pulsate is simply
related to their luminosity. So, by observing the apparent
brightness of a Cepheid and its period of variability it is
straightforward to estimate its distance. Because astronomers
can measure the distance to Cepheids -- and, thus, to the
galaxies they inhabit -- these peculiar stars hold the key to
many important questions in Cosmology.  At today's NAS