Hercules Galaxy Cluster (ACO 2151)

History

The first member galaxies (NGC 6040, NGC 6041 and NGC 6042) had been discovered on 4 June 1869 by French astronomer Édouard Stephan using the the 31-inch Foucault reflector at Marseille observatory. ^[277]

From 6 to 27 June 1886 American astronomer Lewis Swift observed this part of the sky with the 16-inch Refractor at Warner Observatory, Rochester and ten more members of this galaxy cluster: NGC 6039, NGC 6043, NGC 6044, NGC 6045, NGC 6047, NGC 6050, NGC 6055, NGC 6056, NGC 6057 and NGC 6061. ^[277] NGC 6039 is a duplicate entry of NGC 6042: Swift decribed it as «eeeF, vS, R; sp. of 3 in a line; the other 2 being 2 of Stephan's; 3rd of 10». ^[679] The «sp» (south-preceding) in his description is most likely a typing error and should read «sf» (south-following). Then the description «south-following of 3 in a line» matches for NGC 6042, being the other two NGC 6040 and NGC 6041. ^{[196, 204]}

Between 1888 and 1892 Swift, Javelle and Bigourdan discovered further nebulae which were later added to Dreyer's «Index Catalogue». ^[314]

The Hercules Galaxy Cluster was first described by Harlow Shapley in 1933. ^[673] In 1958 George Ogden Abell published his catalogue «The Distribution of Rich Clusters of Galaxies» which contains 2712 clusters identified on the Palomar Observatory Sky Survey (POSS) photo plates. This cluster was listed with the number 2151 and mostly is identified as A 2151 or Abell 2151. ^[674] In 1989 this catalog was extended by Harold G. Corwin Jr. and Ronald P. Olowin with clusters of the southern hemisphere to total 4073 galaxy clusters. ^[675] To prevent identification confusion with Abell planetary nebulae, the galaxy cluster should be identified as ACO 2151, where ACO stands for Abell, Corvin, Olowin. ^[145]

Halton Arp divided his «Atlas of Peculiar Galaxies», published in 1966, into groups based on purely morphological criteria. From Hercules Galaxy Cluster he added four examples: Arp 71 (NGC 6045), Arp 122 (NGC 6040 + LEDA 59642), Arp 172 (IC 1178, IC 1181), Arp 272 (NGC 6050 + IC 1179). ^[199]

Arp 272 (NGC 6050 + IC 1179) — Arp 122 (NGC 6040 + LEDA 59642): Image taken with Hubble Space Telescope. © ESA/Hubble & NASA ^[685]

Physical Properties

The Hercules Galaxy Cluster contains more than 100 members, and spans about 1° section of the sky. Medium distance is about 156 Mpc and it is part of the larger Hercules Supercluster, whic itself belongs to the much larger Great Wall super-structure. Shown below are data of just the brightes members in the 30 arcmin closeup in the finder chart. For more details about the galaxy cluster, see ACO 2151 at CDS.

Revised+Historic NGC/IC Version 22/9, © 2022 Dr. Wolfgang Steinicke ^[277]
Name	RA	Dec	Type	bMag	vMag	B-V	SB	Dim	PA	z	D(z)	MD	Dreyer Description	Identification, Remarks
NGC 6039	16 04 39.5	+17 42 01	dup	14.9	14.0	0.9	13.3	0.8 × 0.7	65	0.034874	147.3		eeF, vS, R, sp of 3 in line	NGC 6042; MCG 3-41-79; CGCG 108-104; DRCG 34-63
NGC 6040 A	16 04 26.7	+17 45 00	Gx (SBc)	15.1	14.2	0.9	13.6	1.3 × 0.7	42	0.042079	177.7		vF, eS, F * close	GC 5799; UGC 10165; MCG 3-41-74; CGCG 108-96; Arp 122; VV 212; DRCG 34-67
NGC 6040 B	16 04 26.5	+17 44 31	Gx (S0)	14.9	14.0	0.9	13.4	0.8 × 0.8		0.040935	172.9		vF, eS, F * close	GC 5799; UGC 10165; MCG 3-41-73; CGCG 108-96; Arp 122; VV 212; DRCG 34-68
NGC 6041 A	16 04 35.8	+17 43 17	Gx (E-S0)	14.4	13.3	1.1	13.5	1.3 × 1.1	36	0.035151	148.4		F, S	GC 5800; UGC 10170; MCG 3-41-78; CGCG 108-101; VV 213; DRCG 34-64
NGC 6041 B	16 04 35.0	+17 43 02	Gx (E-S0)	16.6	15.6	1.0	13.4	0.4 × 0.3	88	0.034777	146.9		F, S	GC 5800; UGC 10170; MCG 3-41-78; CGCG 108-101; VV 213; DRCG 34-65
NGC 6042	16 04 39.5	+17 42 01	Gx (E-S0)	14.9	14.0	0.9	13.3	0.8 × 0.7	65	0.034874	147.3		vF, vS	GC 5801; NGC 6039; MCG 3-41-79; CGCG 108-104; DRCG 34-63
NGC 6043 A	16 05 01.5	+17 46 33	Gx (SB0)	15.3	14.3	1.0	12.8	0.7 × 0.4	55	0.033039	139.5		eeF, pS, lE, "4th of 10"	MCG 3-41-86; CGCG 108-109; DRCG 34-83
NGC 6043 B	16 05 00.7	+17 46 24	Gx (C)	16.2	15.2	1.0	12.4	0.3 × 0.3		0.030981	130.8		eeF, pS, lE, "4th of 10"	MCG 3-41-86; CGCG 108-109
NGC 6044	16 04 59.6	+17 52 13	Gx (S0)	15.3	14.3	1.0	13.0	0.6 × 0.6		0.033106	139.8		eeF, vS, R, vF * close p	IC 1172; MCG 3-41-84; CGCG 108-110; DRCG 34-93
NGC 6045 A	16 05 08.0	+17 45 29	Gx (SBc)	14.9	13.9	1.0	12.8	1.3 × 0.3	82	0.033310	140.7	145.50	eeF, vS, R, v diffic	UGC 10177; MCG 3-41-88; CGCG 108-112; DRCG 34-82; Arp 71; IRAS 16028+1753
NGC 6045 B	16 05 10.3	+17 45 30	Gx (S0)	16.5	15.5	1.0	12.6	0.4 × 0.2	160	0.031184	131.7		eeF, vS, R, v diffic	DRCG 34-81
NGC 6047	16 05 09.0	+17 43 47	Gx (E3)	14.6	13.5	1.1	13.4	1.1 × 0.8	90	0.031262	132.0	112.00	eF, R, pS, F * close n	MCG 3-41-87; CGCG 108-111; DRCG 34-62
NGC 6050 A	16 05 23.5	+17 45 26	Gx (SBc)	15.4	14.7	0.7	13.9	0.9 × 0.6	132	0.031928	134.8	151.50	eeF, S, R, v diffic	IC 1179A; UGC 10186; MCG 3-41-93; DRCG 34-156; CGCG 108-118; Arp 272; VV 220; KCPG 481B
NGC 6050 B	16 05 22.3	+17 45 16	Gx (SBc)	16.0	15.4	0.6	13.7	0.4 × 0.3	35	0.037116	156.7		eeF, S, R, v diffic	IC 1179B; UGC 10186; MCG 3-41-92; DRCG 34-155; CGCG 108-118; Arp 272; VV 220; KCPG 481A
NGC 6054	16 05 38.1	+17 46 03	Gx (SB0)	15.3	14.2	1.1	12.9	0.8 × 0.4	65	0.034010	143.6		eeF, pS, lE, F * sp	IC 1183; MCG 3-41-103; CGCG 108-128; DRCG 34-77
IC 1170	16 04 31.6	+17 43 17	Gx (E-S0)	15.9	14.9	1.0	12.2	0.4 × 0.2	88	0.032166	135.8		vF, vS, vSFN, 6041 f	CGCG 108-101; DRCG 34-66
IC 1178	16 05 33.0	+17 36 07	Gx (E-S0)	15.2	14.1	1.1	13.9	1 × 0.9	36	0.033687	142.2		eeF, pS, bet 2 st	UGC 10188; MCG 3-41-97; CGCG 108-120; DRCG 34-40; Arp 172; VV 194; NPM1G +17.0583
IC 1179 A	16 05 23.5	+17 45 26	dup	15.4	14.7	0.7	13.9	0.9 × 0.6	132	0.031928	134.8	151.50	eeF, pS, R [? 6054]	NGC 6050A; UGC 10186; MCG 3-41-93; DRCG 34-156; CGCG 108-118; Arp 272; KCPG 481B; VV 220
IC 1179 B	16 05 22.3	+17 45 16	dup	16.0	15.4	0.6	13.7	0.4 × 0.3	35	0.037116	156.7		eeF, pS, R [? 6054]	NGC 6050B; UGC 10186; MCG 3-41-92; DRCG 34-155; CGCG 108-118; Arp 272; KCPG 481A; VV 220
IC 1181	16 05 33.9	+17 35 37	Gx (SB0-a)	15.9	14.8	1.1	14.0	0.8 × 0.4	70	0.033066	139.6		eeF, S, R, ‘ 12th of 12 ’	UGC 10189; MCG 3-41-98; CGCG 108-120; VV 194; Arp 172; DRCG 34-39
IC 1182	16 05 36.7	+17 48 10	Gx (S0-a)	15.2	14.2	1.0	12.9	1 × 0.5	81	0.034157	144.2	163.00	vF, S, dif, lbM	UGC 10192; MCG 3-41-104; CGCG 108-126; DRCG 34-78; KUG 1603+179B; NPM1G +17.0584; MK 298
IC 1183	16 05 38.1	+17 46 03	dup	15.3	14.2	1.1	12.9	0.8 × 0.4	65	0.034010	143.6		vF, vS, stellar, * 11 sp 1'	NGC 6054; MCG 3-41-103; CGCG 108-128; DRCG 34-77
IC 1185	16 05 44.6	+17 43 02	Gx (Sab)	14.9	13.9	1.0	12.7	0.8 × 0.5	0	0.034764	146.8		* 13 with S neb	MCG 3-41-110; CGCG 108-134; NPM1G +17.0585; DRCG 34-59

Finder Chart

The Hercules Galaxy Cluster Abell 2151 is located in the constellation Hercules, right beside the head of Serpens. Point your telescope with the widest field of view between the 5.1 mag star r Herculii and binary star κ Herculii (5.0 mag and 6.2 mag, 27" separation). The center of the cluster lies west of the 6.7 mag star HD 144149 and roughly stretches in north-south direction. The galaxy cluster is in opposition to the sun on 23 May and can best be observed in the months of March to October.

Visual Observation

320 mm Aperture: The Hercules galaxy cluster Abell 2151 offered 9 galaxies. Parallel to the three stars arranged at right angles were the two double pairs NGC 6040 A+B and NGC 6041 A+B, along with IC1170, which is located to the left of the latter pair of galaxies, and NGC 6042. The IC 1170 is extremely faint and can only be glimpsed indirectly. Among the double pairs, NGC 6040 A+B is the most difficult pair. The three galaxies NGC 6043, NGC 6045, and NGC 6047 are located below a very wide double star pair. — 12.5" Ninja-Dobson F:4.5 / TV-Radian 8 mm, 181x, 0.33°, Glaubenberg, 7. 7. 2002, Eduard von Bergen