This truly peculiar planetary nebula is placed in the northeast corner of Musca that it shares with the constellations of Circinus and Centaurus. It can be easily found some 2.5°SWW of the brilliant double star Theta (θ) Muscae, or alternatively, 1.7°SSW from the brightest nearby star, m Centauri. Its nebulosity covers an area about 90 x 62 arcsec, with some of the deep optical images extending as much as 138 arcsec or 2.3 arcmin.

Deep within the southern skies and hidden away from most northern hemisphere observers, this remarkable PNe is one of the brightest and most interesting objects of its type, remaining one of the favourites for deep sky observers. Of all the planetaries in the sky, it certainty makes my Top Five and in my opinion, being likely fourth best of all of them. These are against the other main contenders of either;

1. The Helix Nebula (NGC 7293) in Aquarius
2. Dumbbell Nebula (M27) in Vulpecula
3. Eight-Burst Nebula (NGC 3132) in Vela
4. Ring Nebula (M57) in Lyra
5. Blue Planetary (NGC 3918) in Centaurus

Needless to say, of all the southern planetaries, NGC 5189 ranks near the top of my own must see objects! Commonly named the Sprial Planetary, mainly after its visual appearance, which indeed looks more like one of the peculiar morphological type of several loose spiral galaxies. I consider this object one of the most fascinating objects in the Heavens, perhaps because it is simply odd in shape, but more likely because of its uniqueness.

Much confusion remains throughout the literature on the true discoverer of this PNe. It is often stated that John Herschel was first to identify this “...very strange object[1], but it was really the southern deep-sky observer James Dunlop in 1826, one full decade earlier than Herschel. Even the renown southern amateur observer, E.J. Hartung “Astronomical Objects for Southern Telescopes” (AOST1)) has made this error. Dunlop twice observed NGC 5189 from his backyard in Hunter Street, Parramatta using his homemade 23cm. (9-inch) f/12 speculum Newtonian reflector. This is only one of two, or possibly three, southern planetaries that he genuinely identified. Although his described size is far too small, the rest of the information matches the object adequately for identification. He described this particular PNe as No.252 in his catalogue, in which he states; [2]

A very faint nebula, about 25′ diameter. It is very near a star of the 8th mag, and near the north following extremity of a crescent of very small stars.

Dunlop has positioning each deep-sky object he found using his ‘drift-netting’ methods and relying on transits of known stars along the local meridian to determine Right Ascension. Many of the position of these bright stars were also determined at Parramatta Observatory from the bright star survey completed in 1825. [3] In retrospect, this catalogue of deep-sky objects was the natural progression from the significant southern star catalogue first made at Parramatta, New South Wales earlier in this same decade - and merely two hundred metres further east from his home.

In 1835, almost exactly eight years later, John Herschel observed NGC 5189 using his 46cm (18-inch) f/13 speculum telescope. Looking at the catalogued observations of Dunlop, that Herschel had early presented on Dunlop’s behalf to the Royal Society in London, later found Dunlop’#8217s observed position was out by about 54′ - based on Dunlop&#8217s written position at 13h 20m 11s SPD (South Polar Distance) 24o 44′ equally RA 13h 20m 11s Dec -65o 16′ (Epoch 1827). As no other possible known nebulosity was located near Dunlop’s position, we can assume it is very likely this object. Subjectively, Herschel also concluded that NGC 5189 can only be this object, and its proximity being 1.0oN, makes it suspicious, so maybe just some a calculation error. Positions for NGC 5189 (See Table 1);

Table 1 : Positions of NGC 5189

Modern Position 13h 33m 32.39s -65o 58′ 17″ (2000)
Skiff’s Position 13h 33m 32.91s -65o 58′ 26.658″ (2000)
True Position 1828 13h 21m 31.36s -65o 58′ 38″ (1827)
Dunlop’s Position 13h 20m 11s -65o 16′ (1827)

Today, the problem of the exact position of the PN’s true centre continues, however, the best placement so far has been determined by Brian Skiff of Lowell Observatory, in his “Precise Positions for the NGC /IC Planetaries.” (1997), where he points out the problems with positioning; 4] ;

All published positions apply to stars or non-central places. The GSC [Guide Star Catalogue] object position is for the hub of the great bar... which is slightly north of [the] geometric centre. The nebula is quite symmetric however, so this maybe as good as one can do.”

History : An Emission or Planetary Nebula?

Another common error also appears in the “Strasbourg-ESO Catalogue of Galactic Planetaries.” Acker et. al. (1992), which wrongly claims that Williamina P. Fleming discovered NGC 5189 / PNG 307.2-0.34 in 1901, and this is duplicated in many amateur and professional sources. In 1889-99, Fleming was engaged in the search of planetaries by their signature spectra using specific standard photographic methods instigated by the Englishman Edward Pickering. Fleming’s reputation remains as a brilliant astronomical computer, who is often described by others as simply par excellence. In her astronomical career, she had gain some eminence by been involved in the early developments in the stellar spectral classification. [5] Examining each of the southern plates produced by the Harvard Outstation, at Agrippina in Peru, Fleming discovered fifty-nine nebulae, more than 310 variable stars and ten novae. Later, her work produced one of the first Wolf-Rayet star catalogue of 108 objects in 1912. [6,7] Curiously in 1898, finds her own description of NGC 5189 (Fleming 93) as “Planetary, stellar.” [8] However, the stated celestial coordinates are totally correct. Although it was already listed in the NGC, her observation essentially rediscovers the nebula as IC4274. This observation was eventually transposed into Dreyer’s second Index Catalogue. [9] Seeing how NGC 5189 could be viewed as stellar is difficult to understand, as even small spectroscopes show it is obviously nebulose. Perhaps the photographic image of this object was not a good exposure.

Little observation was conducted by anyone for another fifty years. Most of the more modern observations began in the 1950’s, and most included NGC 5189 in the newer photographic surveys; Ie. Colin Gum as Gum 47 (1955), Rodgers as RCW 76 (1960), and the important Karl G. Henize’s Southern PNe Catalogue or abbreviated as He2 in 1966. (Henize lists NGC 5189 as He2-94) When further observations were obtained, the object’s structure remained questionable. Some were still unconvinced of its PNe status. For example, E.J. Hartung states in AOST1 that it is “...a remarkable gaseous nebula”, but at the time it was still thought as a bright nebula and not a planetary. This confusion continues in the many modern atlases and books. Burnham’s Celestial Handbook Vol.2 (BCH2) also lists it as another bright emission nebula.

The beginning of the problems with the type of astronomical body likely started from the original NGC Catalogue published in 1888 by Dreyer. However, Burnham’s description is not exactly the same as Dreyer’s original NGC; “!, B, pl, pE”- Bright, pretty large, planetary emission, while the Revised NGC states it as “B, pl, Ce, bmcurvedaxis, 4' inf”- Bright, pretty large, compressed and extended, four stars involved, but gives none of the modern extensions. Sky Atlas 2000.0 still has it listed as an emission nebula, while Uranometria 2000.0 (U451) and the Sky Cat. 2000.0 Vol.2, has it listed correctly as the PNe. As late as the 1970’s, NGC 5189 remained as a controversial astronomical object. For the modern references, this non-PNe status persisted, mainly from Evans & Thackeray (1950), who stated “...probably not a planetary.”[10]

First to change this wrong viewpoint was Henize (1967) who described the classification as the “ice breaking”. This peculiar object is best classified as quasi-planetary. [11]

The planetary is contained within a brilliant starry field, and can be found, as Andrew Murrell says;

...by finding the two bright stars of about 4.5 mag on the eastern edges of the Coal Sack. Once your finder is centred on these stars you will notice a line of (three) 5th magnitude stars leading away to the southeast. The planetary lies about 20 arc minutes south on top of a 6.5 magnitude star.[12]

In apparent size, the photographic image extends some 3.1x2.2 arcmin and visually about 2.5x1.3 arcmin. Telescopically, some have described it as a boxlike object, but it to me appears more like images of cometary globules - so maybe it should be named the Boxed Cometary Planetary Nebula.

Some have even described it as the Little-Dumbbell, being similar in appearance to its more famous planetary cousin in the constellation of Vulpecula. The terminology is an unfortunate comparison because the PNe M76 in the northern constellation of Perseus is also the Little-Dumbbell. A more recent common name is the Spiral Planetary that has become in vogue because the resemblance to some distant spiral galaxy. Looking at Figure 1, the reason of this latter day name is obvious.

David Frew in AOST2 (1995) describes its features as;

“There is a knot of blueish light east, from which a bright curved bar passes axially west...” [13,14]

The bluish light of this spot is obvious in 20cm f/10 and even perhaps 15cm. In fact, I think all the visible nebulosity has a distinct greenish-blue tinge.

Some sources even claim, that the bright central ‘bar’ regions in dark skies are visible in 7.5cm, but I really doubt this. [15]> I tried this using the 20cm and the 12cm off-axis aperture stop, and I only just saw this faint bar along the axis along PA 60o-240o. Using the full aperture, I had no trouble seeing this bar. I even suspected the slightly curved bar on either end, just as David Frew mentions in the quote above. A 30cm reveals the spiral structure and perhaps some mottling throughout the bar. Andrew Murrell, one of the ASNSWI’s most experienced deep-sky observer, states that this shape poses some challenge for observers, and recommends that the nebulosity is best viewed with high power and a UHC filter - as only to further enhance the contrast. I do not have one of these, so I have to take his word for it. An O-III or Hα filter partly improves the internal structures quite well. AOST2 states that the spiral structure is revealed very easily. David Frew might like to elaborate on this? Apertures above 40cm begin to show significant details within the entire spiral structure, and the PNe disk becomes an indescribable collage of bright and faint spots throughout the nebulosity. Near the end of the central bar, even the bright patches seen in the HST image become apparent. This makes it look like the companion’s ‘sub-galaxies’, like those near Andromeda&8217;s M31. Its no wonder that the object can be confused with other similar shaped spiral galaxies.

Visually 10.0v magnitude, and about 10.5ph, it is classed by the Vorontsov and Velyaminov classification (1934) as Type V or 5 - An irregular form, similar in shape to emission nebulae.

Figure 2a and 2b show the appearance of NGC 5189 in 30cm telescopes. Magnitude limits for each field are about 13.5 and 14.2, respectively. The PNe in both images is also visible in 30cm using the O-III filter. The attached Figure x clearly shows the ring of stars surrounding NGC 5189.

Development of Structural Descriptions of NGC 5189

The quotes about this wonderful object are numerous, so I have selected a few to shows the slow development of this PNe real checkered history. It also reflects our understanding of PNe - especially commonly relating to southern planetaries.

a) J.F.W. Herschel saw NGC 5189 as; [16]

“A very strange object... A nebula of oval figure, but having a central and brighter axis, somewhat curved, and terminating in two masses brighter than the rest; diameter about 90-100 arcsec. It involves 3 stars, one of which with 320 power is double. The principal star is 10th mag; the others extremely, small; a multitude of other stars in field.’

b) W.W. Campbell and J.H. Moore (Pub. Lick Obs.; 13,17 (1918))

“Nebulous field about 1.3′ in length. Composed of three nebulae. NGC 5189, follow[ing] the other three, is about 20 arcsec in diameter, and slightly fainter than the spindle shaped nebulae in the centre.”

This description is interesting, and I assume that the extra nebulae are in likely the two spiral arms of the nebula.

c) Colin S. Gum, in his early 1960’s paper “A Survey of Southern Hα Regions.”; (Mem. R.A.S., LXVII) describes the 47th object in his catalogue as;

“Has been classified as a doubtful planetary nebula [Voronstov-Velyaminov, B.; J.Astron., Soviet Union, 40, (1934)] A photograph by Evans and Thackeray and a drawing by Shapley show a very complex diffuse and knotted structure with no recognisable exciting star. The surface brightness is very high. A peculiar object.”

d) E.J. Hartung (1968) in AOST2 calls it;

“A remarkable gaseous nebula... it lies in a beautiful star field and is bright, about 1.5′xl′ in PA 260o with irregular internal structure and three stars immersed. There is a knot of bluish light following, from which a bright curved bar passes axially west... 7.5cm [telescope] which also shows the irregular structure.”

The problems with the planetary nebulae nature of this object did continue until the mid-1970’s. Ie.

e) Rodgers, Campbell and Whiteoak [RCW Objects - naming NGC 5189; RCW 76]; A&A., 18 (1972)) Similar sources also claimed such confusion, which are assumed to originate from this RCW Catalogue;

“The whole system is enveloped in two lobes of tenuous, patchy material.”

f) Buta, R.J.; W.S. QJ, 66, 1 (1986) (Webb Society Quarterly Journal)

“This is a very fine object in the 24-inch telescope. I saw a large, irregular nebulae that bears a striking resemblance to an S-shaped barred spiral galaxy. The Âúbar is diffuse and splits on one sidee. The armsÂù are patchy and quite extensive, and they arch sharply off the ends of the bar. ...I assume that the catalogues are correct in referring to it as a galactic nebulosity. It looks more like a barred galaxy than some real galaxies I have seen!”

g) John Stanford says (ÂúObserving the Constellations: The Mitchell Beazley Guide to the Stars.Âù; Pub. Mitchell Beazley (1989))

“NGC 5189 is a peculiar nebula whose classification is in doubt. It has an internal structure and several stars are involved Hartung says there is a single prism image which is typical of planetary nebula[e], but other descriptions suggest it is more like a figure ‘8’ or a reflection nebula.”

h) Gregg.G.Thompson,Southern Astronomy; “Deep Sky”, p.38-39 Sept./Oct. (1988)

“One of the most spectacular planetary nebulae is NGC 5189. It is a bright and complex object with a unique form. It is bright enough to be seen in a 10cm. telescope and possibly even smaller apertures in a dark sky... in a 32cm aperture.. [it displays] a shape somewhat to a barred spiral galaxy. The brightest portion is the central star bar-like feature that has separations, bright spots and breaks that are too complex to describe verbally.”
“NGC 5189’s outer regions are faint and arc away to the north and the south. Some bright stars are scattered across the large planetary... measuring about 1.5′arc minutes. An O-III filter makes the object stand out at you even when observed from light-polluted skies... This planetary is estimated at some 1 300 light years distant.”

i) American amateur observer Kent Wallace, in a personal communication, observed this twice (21/01/99 and 07/03/99) and using his C8 form Western Australia, stating;

“...large bright disk. Good response to the O-III and UHC filters. No response to the Hβ Filter. At 100x [I] can see some faint stars involved with the PNe: At 200x the shape of this planetary is strange. Seems to be a central bar crossed on the top and a blob at the bottom.”

j) David Frew and David Malin in AOST2;

“...It lies in a beautiful star field and is bright, about 1.5′x1′ in PA 260o with irregular internal structure and three stars immersed There is a knot of bluish light east, from which a bright curved bar passes axially west; the appearance is strongly reminiscent of a barred spiral, hence its popular name, the Spiral planetary. The single prism image is very clear and may be seen with 7.5cm which also shows a spiral structure. An [O-III] filter gives a strong improvement...”

k) Les Dalrymple (Personal Communication (2000)) while observing from Engadine in Sydney at 12.05am on 19/01/1999 describes NGC 5189 as;

“A thoroughly amazing and intricate object. Difficult to describe shape and structure [is] too complex. Without UHC it appears in the midst of a diamond shaped asterism of 11th mag stars about 5′ x 2.5′ with the diamond in PA 20o. With the UHC it is involved with the western most of these stars. Appears irregular, kind of like a barred spiral eg which has a strong bar and weak stubby arms - sort of like the LMC. The bar is PA 30o, about 1.5′x2.0′ long and starts from a point just east of that west most 11th mag star and leading toward the north most member and getting about halfway there. Bar is irregular and mottled in brightness, and is brightest generally at the SSW end which is also broaden NNE end is a little narrower. At the NE end it seems to curl off toward the SE in PA 140o - stubby. At the other end there is a little extension which leads of from the bar generally West and is less bright and pronounced than its counterpart at the other end. A fairly large area around, roughly circular but slightly elongation in PA 30o is gossamer nebulous.
Central areas are bluish without the UHC. No central star. Thoroughly amazing. SE flank of the bar is probably slightly better defined than the NW.“

l) Alessandro Spina and Andrew James observed NGC 5189 on the 31st March 2000 (11pm) with 25cm Meade LX200. (Universe; 48, 5, p.10 May (2000))

“The first object, and likely the best, was the ‘Spiral Planetary NGC 5189’. Immediately the ‘S’-shape jumped out at us and improved with the O-III filter. Of the four stars embedded inside the object we could only see three. The reason we did not see the fourth star was probably due to the not so good transparency. This object equally impressed a number of onlookers.”
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