BNGC 5. Snow White And Only One Dwarf

By Steve Mencinsky, 1993

The galaxy NGC 253 in sculptor, aka "The Silver Coin", is a superb object in any moderate or large telescope. Indeed, its shape can be discerned in a 50mm finderscope. It was this galaxy that convinced the author of the value of careful sketching through the eyepiece, one evening while observing with David Collis-Bird from Mt. White. David was engrossed in photographing some obscure ring galaxy so yours truly had some time to kill. The original drawing, which took well over half an hour to complete, shows many features that the author had never noticed on the poster, which had occupied his office wall for nearly a year! Unfortunately, like most pencil drawings, the photocopier does not do the sketch justice.

However, back to more immediate business. NGC 253 is one of a very, very select group of galaxies that boasts a companion dwarf galaxy visible to amateur telescopes. This galaxy is clearly visible on both the long and short exposure photographs in Burnhams (pp 1737 and 1738). In fact its non-stellar nature can even be deduced from these photographs by careful comparison with companion stars. David Malin's superb composite-colour photo confirms this, showing it to be completely different to the foreground stars. We may go on to speculate that perhaps this galaxy is similar in nature to the companion of NGC 6744 visible on the famous Collis-Bird photo?

Visually, the dwarf galaxy was at the threshold of the author's vision with the 17.5-inch telescope, and was well within the limit of direct vision of his new 18-inch telescope on the recent very dark night at Ilford. On the 48" Schmidt plates (which according to Rob McNaught go down to magnitude 21) there are no foreground stars nearby, so that if anything is glimpsed in the precise area it is indeed the dwarf galaxy.

The amoeba diagram left is only to show the location of the companion in comparison to NGC 253 and foreground stars. The dwarf galaxy itself is shown as the open circle. No attempt has been made to draw the wonderful detail visible in the main galaxy itself.

NGC 253: (J2000.0) 00h 46m -25° 26'