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RA: 11h 15m 7s
Dec: −61° 15′ 42″
Ch: MSA:991, U2:449, SA:25
Ref: Archinal&Hynes (2003)
Type: open cluster, 23mn
Mag: B=?, V=9.1
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This interesting object was discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "A red star, 10th magnitude, the centre of an excessively condensed group of stars 15..18th mag, with a nebulosity extending over 2' diameter." On a second occasion he "Viewed the nebula ... which is a very remarkable object. The centre, when examined with powers 240 and 320, decidedly not a star, and the nebula about it all resolved. Perhaps it is a globular cluster very suddenly very very much brighter to the middle."
Hinks, A. R. (1911) On the galactic distribution of gaseous nebulae and of star clusters. MNRAS, 71(8), 693-701.
List 6: "NGC numbers of clusters classed as globular, not in Bailey's catalogue"
Bailey, S.I. A catalogue of bright clusters and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.
Trumpler (Lick Obs Bul, Vol 14, No. 420) gives the diameter as 2' and the class as 1 3 m.
Charlier, C V L (1931) "Stellar clusters and related celestial phaenomena", Lund Annals 2, 14, No. 19. Charlier examined prints from the Franklink-Adams atlas; "Table 6 gives a list of those objects in Bailey's catalogue for which the globular character is uncertain or not probable..."
NGC 3603 Remarks: "pB, hazy *"
A Preliminary Survey of Nebulosities and Associated B-Stars in Carina.
Gum, C.S. (1955) A survey of southern HII regions. Mem.RAS, 67. [1955MmRAS..67..155G]
The nebulosity was described by Colin S. GumA Survey of Southern H II Regions published in the RAS Memoirs, Vol. LXVII. He identifies his No. 38a with the grouping NGC 3576, 3579, 3581, 3582, 3584 and 3586. Gum 38b is NGC 3603, and he writes: "Two objects linked together with nebulosity (overall dimensions 45' x 15'). Each is of complex structure." He gives the size of NGC 3603 as 12' x 10' and notes that it is associated with the 9.2 mag star HD 97950. The combined grouping of Gum 38a + b are also known as RCW 57, which is commented with "Appears obscuration-bounded and contains bright crescent shaped region 50' x 20'."
"Cat. of Open Cl. south of -45° Decl.", Mem. 17 Mnt Stromlo Obs.
Sher, D. (1965?) Structure of the Milky Way in Carina. Q.J.R.A.S., 6(3/4), 299.
"NGC 3603 is a cluster of stars less than 1' in diameter surrounded by nebulosty. The cluster itself is small enough to have often been mistaken for a star since its discovery by Sir John Herschel in 1834."
("UBV photometry of star clusters in the Magellanic Clouds", Astronomical Journal, Vol. 73, 1968) find that the integrated V magnitude through a 30'' diaphragm is 8.95. They classify it as an open cluster. They remark "Sher finds V=9.19 from observations on two nights through a 20'' diaphragm."
(Sulentic and Tifft 1973) notes that this is a 10.5 mag open cluster.
by Jim Lucyk: Deep Sky #4 Fa83 p6, Deep Sky #14 Sp86 p38, Deep Sky #11 Su85 p38.
"The distance and neutral environment of the massive stellar cluster Westerlund 1". A&A, 468, 993-1000; arXiv:0704.3073
Call it "a massive Galactic cluster"
& RCW 57
Sher and others: core *s V > 12.5.
15cm - extremely compact knot around m9 sub*ar nuc. UHC works better on neb @ 80x than [OIII], lies mostly S of cl, flattened on N side. 195x: cl 1' diam w/about a dozen m13.5+ *s mostly E of unres sub*ar nuc. cl haze has hisfcbr---lots of *s here. BS, 22Feb1990, LCO.
Hartung notes: "This curious hazy object nearly 2' across seems to be partly gaseous as judged by the prism; there is a central star with many fainter ones clustering round it in the haze, and four-inch will show it."
A 10-inch f/5 at 30x shows this object as dominated by a bright star. Averted vision shows the area immediately surrounding the star as nebulous. It doesn't look like a small globular cluster, because the contrast in brightness between the nebulous envelope and bright centre is too great.
The Messier objects
The Bennett objects
The Caldwell list
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