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RA: 12h 43m 58.17s
Dec: +32° 10′ 9″
Con: Canes Venatici
Ch: MSA:653, U2:108, SA:7
Type: galaxy pair, Im
Mag: B=10.6, V=?
Size: 18.62′ x 3.09′
Select a photo and click the button to view
Synonyms: H I-176
Discovered in 1787 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "Two. The southern [NGC 4656] cB, E, mbM. The northern [NGC 4657] pB, E, sp-nf; Both join and form the letter S."
Dreyer notes that according to Lord Rosse, NGC 4656 and NGC 4657 are connected by faint nebulosity.
Burnham calls it a 11.0 mag peculiar irregular galaxy in Canes Venatici, measuring 19.5' x 2.0', which is pretty bright, large, very much elongated, appearing as an irregular bar with curved ends.
(Sulentic and Tifft 1973) notes that this is a 11.0 mag galaxy. Their coded description reads EL,HISBCT,VKN, DIF EXT SP.
Sandage, A. & Tammann, G. A. (1975) Steps toward the Hubble constant. V - The Hubble constant from nearby galaxies and the regularity of the local velocity field. ApJ, 196, 313-328. [1975ApJ...196..313S]
(1975, Astrophysical Journal, 196, 313-328) includes this galaxy in the Canes Venatici II Cloud. Members include NGC 3675, NGC 4051, NGC 4485, NGC 4490, NGC 4627, NGC 4631, NGC 4656 & NGC 4657.
This galaxy appears on page 40 of "The Hubble Atlas of Galaxies" by Allan Sandage (1961, Washington, DC).
: Sky&Tel. 2/79 p191, Astronomy mag. 5/85 p78, Deep Sky #2 Sp83 p8, Deep Sky #4 Fa83 p34, Deep Sky #22 Sp88 p13, Burnhams V1 p379, Hubble Atl.of Gal. (Sandage 1961) p40.
de Vaucouleurs, G. (1975) Nearby groups of galaxies. In: Kuiper, G. (ed) Stars and Stellar Systems. Volume 9: Galaxies and the Universe. Chapter 14, p557.
This is part of the complex region described as the Canes Venatici (M94) cluster by van den Bergh and as the UMa II group by Sersic. ... a dozen bright objects (NGC 3769 3769A 3949 4051 4088 4111 4143 4242 4485 4490 4625 4618), mainly late-type spirals and irregulars (NGC 4111 and 4143 are lenticulars) form an elliptical core area measuring 15° x 8° ... the overall dimensios of the cloud are increased to 22° x 12° is several probable or possibly outlying members such as NGC 3675 4627 4631 4656/4657 4800 and the dwarf systems NGC 4025 4288 are included.
"nebula, much elongated at 35°, irregular, several nuclei"
Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Hartung notes that it is "not suitable to small apertures. 30cm has shown me a fairly bright centre 1' x 0.5' with a faint pointed ray northfollowing curved at the brighter tip; the southfollowing extension is difficult to see."
Houston notes that the bright NGC 4631 can be used "to locate its dimmer neighbor NGC 4656 about half a degree south-east. It is an amazing sight, an irregular narrow streak almost 20' long and only 2' wide. It is not easy, but on a good night my 4-inch shows it at 100x. Under clear Kansas skies I found it bright in a 10-inch."
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "N4656 = 11M; 14' x 2.5' extent; very large, NE-SW-oriented slash with curved end to SW; little center brightness; NE part brightest; interacting with IRR GAL N4657; see photo at HAG-40; 30' SE of SP GAL N4631; the "Mice" are 25' to SE; !good supernova prospect!."
Subject: Re: NGC 4656/4657
From: Tom Polakis (email@example.com)
Date: Thu, 04 Jun 1998 22:40:56 -0700
] Does anybody know the story behind NGC 4656 and NGC 4657 in CVn?
] Thanks for any help, Tony Flanders, Cambridge, MA
David Knisely is correct that it is one object. The notes in the UGC (1974) refer to it as two interacting systems, but a more recent paper from 1983 (AJ 88,602) which presents surface photometry says that NGC 4656 and 4657 appear to be parts of the same galaxy. The authors make comparisons between the galaxy and NGC 55 and the Small Magellanic Cloud. NGC 4656/7 has very similar luminosity and size as the SMC, although it is tidally distorted. There are obvious signs of interaction with nearby NGC 4631 in radio wavelengths, but they didn't show up optically in this study.
On the amateur side, I like to call this galaxy "The Hockey Stick" -- especially this time of year!
6cm - barely vis 10' SW of m10 *.
7cm - vis as second much fntr spindle in fld w/N4631 @ 30x. broad brtning
along length, wkly mottled. BS, 26Apr1993, Anderson Mesa.
15cm - 8'x1' in pa35. mottled. somewhat brtr center, more pronounced than in
25cm - 12'x1'.
30cm - pa50, 9'x1'.2 incl the appendage -57. SW end exceedingly f, but has a
not-so-faint patch at its end. the core is blobby w/two parts. the bridge
btwn -56 and -57 is of higher sfcbr and smoother. -57 curves off NErn end
in about pa90. it has two brtr patches in it, the Wrn one lgr/brtr than
Instrument:12"Dobsonian Reflector Telescope.
Sky Condition:The fainter parts of the Milky Way are barely visible.
Transparency of the Sky:Haziness only visible on the horizon.
Seeing:Atmosphere stable with little interference.
Chart Number:No.5(Extract taken out of "Atlas of the Night Sky").
Size:26mm Eyepiece:Field Of View:57'/4=14.2'.
20mm Eyepiece:Field Of View:50'/3.5=14.2'.
Size in Arc Minutes:14.2'.
Brightness Profile:Low Surface Brightness.
Challenge Rating:A fantastic sight under crisp clear dark skies under a very large telescope.
This galaxy is well observed as a large irregular galaxy with
well defined structure.This galaxy's shape takes the form of a hockey-stick or humingbird.This galaxy's strange appearance is easily noticeable with dark dust lanes.Close to this galaxy,I have found some darker areas within the vicinity of this galaxy while this galaxy does not have a central nucleus.On the outskirts of this galaxy uneven brightness is observed on the outskirts of this galaxy.
Observing site: Little Bennett Regional Park
[12h 44m 0s, 32° 10m 0s] A very nice, if faint, edge on. About 10' long. B:I/pec. WikiSky: edge on with twisted ends.
The Messier objects
The Bennett objects
The Caldwell list
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