Caldwell 72

This galaxy is similar to, but smaller than, the Large Magellanic Cloud.

Distance

6.5 million light-years

Apparent Magnitude

7.8

constellation

Sculptor

object type

Irregular/Dwarf Spiral Galaxy

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.

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)

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. 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.

At lower left, a ground-based image of Caldwell 72 (NGC 55) from the European Southern Observatory (ESO) includes a box showing the region near the galaxy’s core that’s captured in Hubble’s Advanced Camera for Surveys (ACS) image.Credits: Ground-based image: European Southern Observatory; Hubble ACS image: 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)

Ground-based image: European Southern Observatory; Hubble ACS image: 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)

At top right, a ground-based image of Caldwell 72 (NGC 55) from the European Southern Observatory (ESO) includes an outline of an interesting part of the galaxy imaged by Hubble’s Wide Field and Planetary Camera 2 (WFPC2), shown at lower left.

Ground-based image: European Southern Observatory; Hubble WFPC2 image: NASA, ESA, and J. Dalcanton (University of Washington); Processing: Gladys Kober (NASA/Catholic University of America)

The mosaic at the bottom captures countless stars in an outer portion of the disk of Caldwell 72 (NGC 55). It was created from multiple observations taken in visible and infrared light by Hubble’s Wide Field and Planetary Camera 2 (WFPC2). The ground-based image of the galaxy from the European Southern Observatory (ESO), at top right, shows the part of the galaxy captured in the Hubble mosaic.

Ground-based image: European Southern Observatory; Hubble image: NASA, ESA, and J. Dalcanton (University of Washington); Processing: Gladys Kober (NASA/Catholic University of America)

This star chart for Caldwell 72 represents the view from mid-southern latitudes for the given month and time.

Image courtesy of Stellarium

Glossary

Apparent Magnitude - The brightness of an astronomical object as seen from Earth, influenced by the object's distance from Earth, its absolute magnitude, and even gas and dust that lie between the object and Earth.

Dwarf Galaxy - A small, faint galaxy with only millions to a few billion stars.

Irregular Galaxy - A galaxy that lacks a defined shape or structure.

Satellite Galaxy - A galaxy that is gravitationally bound to a larger galaxy, much like how the planets in our solar system are gravitationally bound to the Sun.

Spiral Galaxy - A galaxy characterized by its spiral structure, with star-filled arms that extend out from the center of the galaxy and host regions of star formation.

Explore Hubble's Caldwell Catalog

The following pages contain some of Hubble’s best images of Caldwell objects.

Stars with four diffraction spikes dot the scene against a black backdrop.

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