2 Attachment(s)
Object of the Week - May 15th, 2016 - NGC 4933 - Arp 176
NGC 4933 (IC 4173, IC 4176) = Arp 176
R.A.: 13h03m58s
Dec.: -11°29'52" (2000)
Size: 2.6'
Mag: 12.1v (A), 14.2v (B), 16.1v (C)
Galaxy Triplet in Virgo
First one, who else, was F.W. Herschel, who describes "the" galaxy as "pretty bright, pretty large and irregular round" in 1784. Some confusion started by Bigourdan (1895) who misidentifies one of the galaxies as a star and cataloged two new IC numbers.
After high resolution photography identifies the "one" NGC number as a (in my mind very unusual) galaxy group, Arp gets in touch with the peculiar group and listed the object under number 176 as group: "narrow counter-tails". His notes add a "very condensed" for the companion galaxy NGC 4933A. Interesting fact is, that Vorontsov-Velyaminov missed the peculiar trio in his former catalogue.
Unfortunately scientific papers are very rare around this group. It seems that NGC 4933A and NGC 4933B are interacting and forms a merging pair while NGC 4933C although its same distance around 48Mpc forms an irregular non-merging companion. Beside the merging effects, three other details are interesting, especially in the visually context:
- NGC 4933B shows strong dark lanes to the NW,
- the inner structure forms a larger knot directly NE of the core of NGC 4933B which looks like a fourth galaxy through the telescope
- NGC 4933A shows a 0.5' tail to the SW
All details are displayed very good at the Carnegie-Irvine Galaxy Survey which was made through the 2.5m telescope at Las Campanas.
But what could be visible through what aperture? After stumbling over the nice trio with my 27" I started a quick and dirty session with other telescopes.
The view through a large telescope is stunning! Perhaps my best discovery last new moon. The trio was completely visible with the described knot and the tail of NGC 4933A. More difficult were the dark lanes. I only suspected the brighter lane as a harder edge NW of the core of NGC 4933B.
The 16" shows also all three galaxies. NGC 4933C was difficult but could be hold with averted vision. No sign of the dark lanes or the tail. Even my small 8" shows both NGC 4933A and NGC 4933B with direct vision as a nice pair of galaxies in contact. I noted "looks like Minkowski's Footprint through a larger telescope.
labeled DSS (15'x15' red)
Attachment 2102
sketch: 27", 419x-586x, Seeing III, NELM 6m5+
Attachment 2103
