mei 282013

May 28, 2013

NGC 1531 and NGC 1532, interacting galaxies in Eridanus

NGC 1531 and NGC 1532, a pair of interacting galaxies in Eridanus

Image Credit & Copyright: Robert Gendler, Jan-Erik Ovaldsen, Allan Hornstrup, IDA; Image Processing: Robert Gendler (

NGC 1531 and NGC 1532 are a pair of interacting galaxies located about 55 million light-years away from Earth in the southern constellation of Eridanus (the River). They are outlying members of the Fornax Cluster of galaxies.

NGC 1531 – the small background galaxy with a bright core that lies just above the center of its companion – is a lenticular dwarf galaxy of about 20,000 light-years across. It is receding from us at approximately 1169 kilometers per second.

NGC 1532, the large foreground galaxy laced with dust lanes, is a nearly edge-on, deformed barred spiral galaxy of about 180 thousand light-years across which is receding from us at about 1040 kilometers per second. It may possess several dwarf companion galaxies, but is clearly interacting with NGC 1531.

These galaxies lie so close together that each feels the influence of the other’s gravity. As a result NGC 1532 became distorted: one of its spiral arms is warped and plumes of dust and gas are visible above its disk. The interaction has also triggered bursts of star formation in both galaxies. Especially in NGC 1532 a whole new generation of massive stars has been born, visible as the purple objects in the spiral arms.

In addition, material may have been transferred to NGC 1531, which shows an S-shaped dust lane crossing its center. Over time the gravitational interaction of the two galaxies will tear the smaller galaxy apart and merge its remains with the larger one.

This image was made using the 1.5-metre Danish telescope at the ESO La Silla Observatory, Chile, 2008. It is based on data obtained through three different color filters.

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