Hubble Space Telescope image of the spiral system NGC 4603, which lies more than 100 million light-years away in the constellation Centaurus (The Centaur). Credit: ESA / Hubble & NASA, J. Maund
This image shows a close-up portrait of the magnificent spiral system NGC 4603, which lies more than 100 million light-years away in the constellation Centaurus (The Centaur). Bright bands of blue young stars form the arms of this galaxy, which curl from the meandering core. The intricate reddish-brown filaments that thread through the spiral arms are known as dust webs and consist of dense dust clouds that obscure the diffuse starlight of the galaxy.
This galaxy is a familiar subject for Hubble. In the last years of the twentieth century, NGC 4063 was closely and closely watched for signs of a peculiar class of stars, known as Cepheid variables. These stars have a luminosity that is closely linked to the period in which they darken and illuminate, so that astronomers can accurately measure how far they are from Earth. Distance measurements of Cepheid variables are the key to measuring the farthest distances in the Universe, and were one of the factors used by Georges Lemaître and Edwin Hubble to show that the Universe is expanding.