Object of the Week, December 12, 2021 – NGC 750/751 = Arp 166 - Triangulum
Object of the Week, December 12, 2021 – NGC 750/751 = Arp 166 - Triangulum
R.A.: 01h57m32.8s
Dec.: +33°12'34"
Size: 1.5'x 1.4'; Magnitude: 12.9
NGC 750 and NGC 751 are interacting elliptical galaxies about 225 million light-years away in Triangulum that are well-placed for observing this month. The pair is listed as Arp 166 in the Atlas of Peculiar Galaxies (in the category Galaxies with diffuse filaments). It is interesting to note that Herschel discovered NGC 750 on September 12, 1784, and he did not resolve it as a pair, but rather as a single object… so it took another 66 years before the Irish astronomer Bindon Stoney was able to find NGC 751 hiding in the glare of its brighter big brother on October 11, 1850, using Lord Rosse's 72" telescope.
In my 25” f/5 Obsession dob I can see the cores of each galaxy lined up almost exactly north and south with NGC 750 being the northern component, and they are surrounded by what appears to be a common haze of nebulous galactic material, looking pretty much like most other amorphous elliptical galaxies, that is, without any structure or character to speak of. I would guess that the cores are about 20” apart. Wiki tells me there is a tidal tail but I saw no sign of it!
There are a number of other galaxies in the area to explore, which is why I decided to write about Arp 166 in the first place… I should have said NGC 750/751 and friends!
NGC 761 is about 11’ NNE of NGC 750, a barred lenticular galaxy, mag 14.4, a barred lenticular galaxy, small, elongated, and faint but easy enough to see.
NGC 739 is about 9’ NW of NGC 750, and is another lenticular galaxy, even smaller than NGC 761 and even dimmer at mag 15… but still available with direct vision on a good night. There was apparently some discrepancy about the position of this guy and Steve Gottlieb has details in his great NGC notes… https://www.astronomy-mall.com/Adven...(11-30-17).htm
NGC 736 is about 14.5’ SW of NGC 750 and is almost a twin to NGC 750, being an elliptical galaxy a little brighter at mag 12.1, but he has (4) NGC galaxies close by that should all be in the same field of view with moderate magnification. NGC 740 is the brightest companion about 3.4’ SE, mag 14.8, NGC 738 is the closest and dimmest companion about 1.5’ NE mag 15.9, and NGC 733 is about 3.5’ WNW, at about mag 16… and with some ID issues, which are once again are addressed by Steve G. in his notes.
If you reference the chart you will see that there are still more galaxies in this area, so go ahead and see how many of them you can detect!
As an added bonus there is a nice double star about 4.5' SE of NGC 750, ADS 1562, mags 9.4and 9.9 with a separation of 1.7", an easy split on a night of good seeing.
As always, give it a go and let us know.
Last edited by Paul Alsing; December 15th, 2021 at 02:57 AM.
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