Images of a Galaxy in the Fornax Cluster of Galaxies

This color image from the Hubble Space Telescope shows a region in NGC 1365, a barred spiral galaxy located in a cluster of galaxies called Fornax. A barred spiral galaxy is characterized by a "bar" of stars, dust and gas across its center. The black and white photograph from a ground-based telescope shows the entire galaxy, which is visible from the Southern Hemisphere. Members of the Key Project team, who have been measuring the distance to the Fornax cluster, have estimated it to be 60 million light-years from Earth. The team arrived at their preliminary estimate by using Cepheids, bright, young stars that are used as milepost markers to calculate distances to nearby galaxies. The line of small blue dots in the color image shows the formation of stars in the galaxy's spiral arms, making them ideal targets for the discovery of Cepheids. The group has discovered about 50 Cepheids in the galaxy. The team also has used the Fornax cluster to calibrate and compare many secondary distance methods. Cepheids are accurate distance markers for nearby galaxies, but astronomers need secondary methods to measure distances to faraway galaxies. An accurate value for the Hubble Constant is dependent on reliable secondary distance methods.