Caldwell 72, also known as NGC 55, is a galaxy located 6.5 million light-years from Earth in the constellation Sculptor. It was discovered by Scottish astronomer James Dunlop in 1826, when he resided in Australia. Caldwell 72 is best observed in the Southern Hemisphere during the spring, although it can also be viewed from southern parts of the Northern Hemisphere in the autumn. The galaxy has an apparent magnitude of 7.8 and can be spotted with a pair of binoculars under dark skies.

Caldwell 72 is classified as a Magellanic-type galaxy. The classification is named after the Large Magellanic Cloud, a satellite of our Milky Way galaxy. Galaxies of this type have a single spiral arm and are an intermediate class between irregular galaxies and dwarf spiral galaxies. Morphologically, Caldwell 72 very closely resembles the Large Magellanic Cloud, but is smaller and has an edge-on orientation.

This image, showing a central part of Caldwell 72, is a composite of visible and infrared observations made by Hubble’s Advanced Camera for Surveys. The observations were taken to help astronomers understand how the distribution of the galaxy’s relatively small structures, such as dust clouds, affect how the light from the galaxy is dimmed as it passes through this intervening matter. Because light from the galaxy is partially obscured by the dust along our line of sight, it is important that we understand its small-scale distribution.

Credit: NASA, ESA, R. de Jong (Leibniz-Institut fur Astrophysik Potsdam [AIP]), and G. Illingworth (University of California – Santa Cruz); Processing: Gladys Kober (NASA/Catholic University of America)