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IC 1805 (1,754 of 18,648)

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Heart Nebula

IC 1805, Cl Melotte 15, Cl Collinder 26, Raab 11, COCD 33, LBN 654, Sh 2-190, Ced 7, Heart Nebula

RA: 02h 32m 42s
Dec: +61° 27′ 24″

Con: Cassiopeia
Ch: MSA:46, U2:17, SA:1

Ref: SIMBAD, DAML02, Archinal&Hynes (2003)

(reference key)

Type: open cluster, 23mn

Mag: B=7.03, V=6.5

Size: 20′
PA: ?

Image gallery

Photos  (1)

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History and Accurate Positions for the NGC/IC Objects (Corwin 2004)

IC 1805. Barnard's RA is off by about 50 seconds of time (this seemed to happen a lot with his observations; see e.g. IC 1802). Still, the cluster, immersed in a huge nebula, is too obvious to be missed. Barnard called it "compressed", so I've taken it to be the small cluster centered to the east of HD 15558. Brian Skiff puts the HD star closer to the center, and so takes the cluster to include many more of the surrounding stars. In this case, the group that I include is just the core of the cluster. I suspect Brian is right.

Also see IC 1831 for another possible object in the area.

Remarks

The object is associated with the Cas OB6 association.

Because of its appearance on astrophotos, it has the nickname "Heart Nebula", possibly coined by Matt BenDaniel, US astrophotographer. Nearby IC 1848 is nicknamed the "Soul Nebula".

Historical observations

Barnard, E.E

Described by Barnard as a cluster, compressed, with extremely large nebulosity extending east. The bright emission nebula associated with this open cluster is about 1 square degree in size.

Published comments

Melotte, P.J. (1915)

A catalogue of star clusters shown on Franklin-Adams chart plates. Mem.R.A.S., 60(5), 175-186.

Melotte 15: A very loose cluster. Somewhat similar to NGC 1027 but stars not so numerous and generally brighter.

Diam 20

Raab, S. (1922) "A research on open clusters"

Melotte 15: Based on F-A plates: "An irr. but well-defined cl. Most of the * are lying close together at the centre from which several offshoots branch off in irregualr form."

Doig, P. (1926)

"A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.

Melotte 15: "Very loose cluster, irregular but well defined; with diffuse nebulosity." He gives the approx. diameter as 23 arcmin.

Trumpler, R.J. (1928)

(Lick Obs Bulletin, Vol 14, No. 420) gives the diameter as 20' and the class as 4 3 m. He adds that there is nebulosity involved with the cluster.

Cederblad, S. (1946) [VII/231]

Ced 7 (IC 1805)

Position (1900): RA 2 24.5, Dec + 61 2

Star: Cl (Mp=6.0, , SpT=B0?)

Spectrum of nebula: emission spectrum (observed)

Classification: Nebulous cluster (milky neb cover the clusters, eg NGC 1976)

Size: 50'x44'

Notes: "IC 1805. Disc. Barnard. (93 Pl 1 Pl 2, 194, 216, 482, 486, 571, 630 Pl 26 Pl 27, 726 No 27, 753). R. Nebulous cluster containing the BD stars: +60 496-502, 504-509, 511-513. +60 502 = HD 15558. +60 504 = HD 15570. +60 507 = HD 15629. The spectra of these stars are stated to be "perhaps B0". There is a conspicuous condensation at +60 507."

Lynds, B.T. (1965)

(Astrophysical Journal Supplement, No 105, 1965) in her Catalogue of Bright Nebulae notes that this nebula is moderately bright, more prominent on the red POSS plate and has a maximum size of 60' x 60'.

Photo index

by Jim Lucyk: Sky&Tel. 1/70 p4 (red-light POSS print), Vehrenberg's Atlas of Galactic Neb-1 p15, 17. Astronomy mag. 11/85 p51, Deep Sky #7 Su84 p24, Deep Sky #17 Wi86 p17, Vehrenberg's Atlas of DS Splendors (3ed) p41, Vehrenberg's Atlas of Galactic Neb-1 p15, 17, The Astrograph 4-5/88 p68,69.

Vehrenberg's Atlas of DS Splendors (3ed) p41

Modern observations

Neilson, David (1992)

Neilson (Oakland, California, USA), writes in The Webb Society Nebulae and Clusters Section Report No. 10, July 1992: "Curious nebula with faint condensation surrounding Melotte 15 open cluster (12.8-inch)."

Tom Lorenzin

Melotte 15:, in the electronic version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "6.5M; 20' diameter; 20-plus 7M members; surrounded by nebulosity I.1805, mostly to ESE; large, faint OPN CL N1027 1 degree E and a little N; DIF NEB I.1795 (10' diameter) soft and splotchy and 1 degree to NW; large nebulosity complex I.1848 2.5 degrees ESE; use N-filter for these emission nebulae; reference photo at VADSS-41."

Brian Skiff

Mellotte 15/gn I1805 [~N960]

7cm - lg mod br cl @ 30x showing fairly f neb. 50x: 20' diam w/40 *s, brtst is m7 in center. outliers merge smoothly w/bkgrnd. broad concen mostly except close to br cen *, where it is sharp. BS, 26Nov1992, Anderson Mesa.

8cm - consp cl of 25 *s well res in vf haze @ 20x. BS, 17Oct1982, nderson Mesa.

15cm - lg rel poor but well concen cl surrounding m7,10 dbl in center. cl distinctive even @ 30x. 25' diam w/75 *s @ 80x. the haziness of the neb is vwk w/o UHC at any power. at 30x w/UHC, the loop from I1795/N896 goes nrly S to oc Ma 6 then E and sl N, curling suddenly around to E side of Mel 15, where there's a pretty big blob that extends right over cl itself (doesn't look like scattered cl *light, but maybe). this blob centered 1/3 way from Mel 15 to N1027. BS, 11Dec1990, Anderson Mesa.

25cm - lg, loose. ten br *s and as many f members. 20' diam. no neb seen.

30cm - br. m8.5 & 9 *s overflow 22' fld to 25' diam. surrounding a * nr center is a cl of fntr ones; 25 *s in 5' area. not much for 30cm.

Contemporary observations

Tom Bryant

2010 10 21 21:27:54

Observing site: Little Tycho Observatory

Telescope: C-8

[2h 32m 42s, 61 27m 0s] A wide grouping of around 8 9mv stars with about 20 11... fainter ones. Many of these stars appear double. A nice star field.

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