NGC 1532 — Galaxy in Eridanus

NGC 1532 is a large edge-on barred spiral in Eridanus, about 57 million light-years away, locked in a tidal interaction with the smaller, lenticular companion NGC 1531 sitting just to its northwest. The encounter has visibly warped NGC 1532's disk: its northern flank is bent upward and out of the plane while its southern side trails a tidal stream of stars and gas. The pair is one of the cleaner local examples of a major-disk galaxy mid-encounter with a smaller neighbour. At magnitude 9.9 with a striking 12-arcminute long edge-on profile, NGC 1532 is a fine telescopic target.

From a dark site, a 4-inch at moderate power shows an elongated bright streak with a soft halo. An 8-inch at 150-200x reveals the clearly asymmetric disk and the small bright companion NGC 1531 just north of the western end — the pair fits comfortably in the same eyepiece field. A 12-inch begins to bring out the warp and dust lanes along the southern edge. NGC 1532 sits at declination -33 degrees and skims low for northern observers; it is best from southern locations. Best observed October through February.

Discovered by James Dunlop on 29 October 1826 from Parramatta. The interaction with NGC 1531 was first systematically studied in the 1970s, and the system became a frequently cited example in early N-body simulations of galaxy encounters because of its clean geometry and relatively isolated environment.