One of the important discoveries of the present century is that the Universe expands. Two important parameters which define the dynamics of the Universe and can be obtained at the telescope are the rate of expansion zhqо
, and change of this rate with time qо
, It is difficult to derive a value for Hо
because accurate distances of farther galaxies are needed. This involves identifying the luminous objects, such as brightest stars, HII regions, globular cluster, supernova etc., in the Local Group galaxies as well as in the external galaxies. Once the absolute magnitudes of these objects are calibrated with the known distances of the Local Group galaxies, distances to the external galaxies can be derived.