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eta Carinae Nebula

Lacaille III.5, Lacaille III.6, Dunlop 309, NGC 3372, Ced 109, Gum 33, RCW 53, Caldwell 92, eta Carinae Nebula, h 3295, GC 2197

RA: 10h 44m 19s
Dec: −59° 53′ 21″

Con: Carina
Ch: MSA:992, U2:427, SA:25

Ref: SIMBAD

(reference key)

Type: bright nebula (HII region)

Mag: B=?, V=?

Size: ?
PA: ?

Image gallery

Sketches  (7)

Select a sketch and click the button to view

Photos  (28)

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Remarks

The giant Eta Carinae nebula is some 300 light years across, twenty times the size of the Orion Nebula. Although it is 9000 light years away, it stretches across two degrees of sky.

The nebula takes the form of three enormous fan-shaped areas with dark lanes between. In the telescope, the main area containing Eta itself is brightest, and the dark lanes set it off with very definite borders. The distinctively shaped Keyhole Nebula is the most famous dark zone seen near Eta, and is more prominent to the eye than in long-exposure photos.

Wide-field photo, good for visual comparison, in Astronomy, 1993, June, p 83.

Online resource

Eta Carinae: General Information, the 2003 spectroscopic event, and the HST Treasury Project

A website maintained by the eta Car research group, University of Minnesota.

http://etacar.umn.edu/

"This site includes technical information for both professional and advanced non-professional astronomers. However, material here may be of interest to others as well -- especially scientists, science writers, and amateur astronomers. Here you can find references, data, links, images and figures, updates and more."

Historical observations

Lacaille (1755)

It was discovered by Lacaille and included in his 1755 catalogue as Class III Nos. 5 & 6. In his half-an-inch 8x telescope he saw it as "many faint scattered stars in circle 15-20 minutes diameter filled with nebulosity."

John Herschel (1847) Cape Observations

Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. In his great work "Results of Astronomical Observations made during the years 1834,5,6,7,8, at the Cape of Good Hope; being the completion of a telescopic survey of the whole surface of the visible heavens, commenced in 1825, by Sir John F. W. Herschel, Bart., K.H. ... " published in 1847 he writes about "Eta Argus and the great Nebula surrounding it. There is perhaps no other sidereal object which unites more points of interest than this. Its situation is very remarkable, being in the midst of one of those rich and brilliant masses, a succession of which curiously contrasted with dark adjacent spaces (called by the old navigators coal-sacks), constitute the milky way in that portion of its course which lies between the Centaur and the main body of Argo. In all this region the stars of the milky way are well separated, and, except within the limits of the nebula, on a perfectly dark ground, and on an average, or larger magnitudes than in most other regions." Herschel then gives the results of several star counts or "star gages" conducted over an area of 47 square degrees, and concludes that: "the amazing number of 147,500 stars must have passed under review. In the midst of this vast stratum of stars occurs the bright star Eta Argus, an object in itself of no ordinary interest on account of the singular changes in its lustre has undergone within the period of authentic astronomy." He then relates a short history of Eta's magnitude as seen by observers before him, starting with Halley in 1677 and ending with Taylor's observation in 1833 which recorded it as second magnitude. "When first observed by myself in 1834, it appeared as a very large star of the second magnitude, or a very small one of the first, and so it remained without apparent increase or change up to nearly the end of 1837, in November of which year it was noticed of its usual brightness, or at least without exciting any suspicion of a change ... It was on the 16th December 1837 that ... my astonishment was excited by the appearance of a new candidate for distinction among the very brightest stars of the first magnitude, in a part of the heavens with which being perfectly familiar, I was certain that no such brilliant object had before been seen. After a momentary hesitation, the natural consequence of a phenomenon so utterly unexpected, and referring to a map for its configurations with the other conspicuous stars in the neighbourhood, I became satisfied of its identity with my old acquaintance Eta Argus. Its light was however nearly tripled. While yet low it equalled Rigel, and when it had attained some altitude was decidedly greater. It was far superior to Achernar. Fomalhaut and Alpha Gruis were at the time not quite so high, and Alpha Crucis much lower, but all were fine and clear, and Eta Argus would not bear to be lowered to their standard. It very decidedly surpassed Procyon, which was about the same altitude, and was far superior to Aldebaran ... From this time its light continued to increase. On the 28th December it was far superior to Rigel, and could only be compared with Alpha Centauri which it equalled, having the advantage of altitude, but fell somewhat short of it as the altitudes approached equality. The maximum of brightness seems to have been obtained about the 2nd January 1838 ... it was judged to be very nearly matched indeed with Alpha Centauri ... After this its light began to fade ... On the 20th, it was 'visibly diminished - now much less than Alpha Centauri, and not much greater than Rigel. The change is palpable.'" He continues to discuss the course of the outburst, and notes that "a strange field of speculation is opened by this phenomenon." He ends the discussion with the observation that: "in the beginning of 1838, the brightness of this star was so great as materially to interfere with the observations of that part of the nebula surrounding it which is situated in its immediate vicinity, and, in particular, almost to obliterate that extremely curious oval or lacuna which forms to conspicious a feature in the figure of the nebula annexed, and of which, had I not previously secured a correct representation, I should then scarcely have been able to have done so to my own satisfaction. The accurate representation of this nebula with its included stars has proved a work of very great difficulty and labour, owing to its great extent, its complicated convolutions, and the multitude of stars scattered over it. To say that I have spent several months in the delineation of he nebula, the micrometrical measurement of the co-ordinates of the skeleton stars, the filling in, mapping down, and reading off of the skeletons when prepared, the subsequent reduction and digestion into a catallogue, of the stars so determined, and the execution, final revision, and correction of the drawing and engraving, would, I am sure, be no exaggeration. Frequently, while working at the telescope on these skeletons, a sensation of despair would arise of ever being able to transfer to paper, with even tolerable correctness, their endless details. However, by breaking it up into parts, and executing each part separately, it has been accomplished ..." This account gives us a rare glimpse of Herschel the man and sets an example for all deepsky observers. Herschels magnificent sketch spans almost exactly a square degree of sky: "Of this about four-sevenths are occupied by the nebulous branchings and their included vacuities, and this portion only I have thought it requisite to triangulate and catalogue. The number of stars within this area whose places have been determined is 1,203 ... " In the introduction to his discussion of the nebulosity, he comments: "It would manifestly be impossible by verbal description to give any just idea of the capricious forms and irregular gradations of light affected by the different branches and appendages of this nebula. In this respect the figure must speak for itself." Of the surrounding sky in which the nebula is situated, he writes: "Nor is it easy for language to convey a full impression of the beauty and sublimity of the spectacle it offers when viewed in a sweep, ushered in as it is by so glorious and innumerable a procession of stars, to which it forms a sort of climax, justifying expressions which, though I find them written in my journal in the excitement of the moment, would be though extravagent if transferred to these pages. In fact, it is impossible for any one with the least spark of astronomical enthusiasm about him to pass soberly in review, with a powerful telescope and in a fine night, that portion of the southern sky which is comprised between 6h and 13h of RA, and from 146 to 149 NPD [-56 to -59 Declination], such are the variety and interest of the objects he will encounter, and such the dazzling richness of the starry ground on which they are represented to his gaze." A footnote reads: "The first three hours of the zone thus marked out are remarkable for their fine double stars. Among the nebulae which occur from 9h to 12h we have .. the beautiful planetary nebula [NGC 2867], a perfect planet in appearance, with an attendant satellite; the falcated nebula [NGC 3199]; Eta Argus with its nebula; the superb cluster [NGC 3532]; the blue [Herschel's italics] planetary nebula [NGC 3918], a most exquisite and unique object ; and the beautiful cluster of various coloured stars about Kappa Crucis [NGC 4755]." Hershel incorrectly deduces that the nebulosity lies "at an immeasurable distance behind that stratum [Milky Way]", since "this nebula does not show any appearance of resolvability into stars ... [and] has therefore nothing in common with the milky way, on the ground of which we see it projected." Of the appearance of the nebulous complex, he writes: "There are, however, certain features to which it is necessary to refer more particularly in illustration of our figure ... The whole extent of the nebulosity to the south is somewhat greater than can be included in the figure, but it grows so faint beyond the oval vacuity in the upper part that I have not considered it necessary to trace it beyond that limit. Nor am I quite sure that the south following portion of the area of the figure in which no nebula is represented is in reality absolutely free from it. The interior of the oval above mentioned is perfectly so. It is also nearly devoid of stars, four minute ones ... only having been perceived in it." Herschel was concerned with the possibility of change taking place in the nebula, and wrote: "Great attention has been paid to exactness in the situations of the minute stars ... which mark out the form of this oval with respect to its borders. The two large stars .. on its south following side are fairly immersed in the nebula, as are also [a star] on its south preceding, and [two stars] at its northern extremity. Close to the great star A, is situated that singular lemniscate-oval vacuity which forms so strange a feature of this nebula. Its area is not entirely devoid of light. A thin nebulous veil seems as if extended over its northern loop on the preceding side. Four stars .. are placed precisely on its edge, and will serve as excellent detectors of change in its form, should any occur..." The rest of his discourse relates to the measurement and construction of the system of skeleton stars he employed to accurately draw the nebula.

Dunlop, James (1827)

James Dunlop observed it from Paramatta, New South Wales, and included it as No. 309 in his catalogue of 1827. Using a 9-inch f/12 telescope to observe it, he wrote: "(Eta Roboris Caroli, Bode) is a bright star of the 3rd magnitude, surrounded by a multitude of small stars, and pretty strong nebulosity; very similar in its nature to that in Orion, but not so bright ... I can count twelve or fourteen extremely minute stars surrounding Eta in the space of about 1'; several of them appear close to the disk: there is a pretty bright small star about the 10th magnitude N.f. the Eta, and distant about 1'. The nebulosity is pretty strongly marked; that on the south side is very unequal in brightness, and the different portions of the nebulosity are completely detached, as represented in the figure. There is much nebulosity in this place, and very much extensive nebulosity throughout the Robur Caroli, which is also very rich in small stars." Dunlop observed it 13 times.

Herschel, L. & Herschel, J. W. F. (1869)

Herschel, L. & Herschel, J. W. F. (1869) The Great Nebula around eta Argus. M.N.R.A.S., 29, 82-88.

Burton, C. E. (1875)

On the Southern Nebulae 30 (Bode) Doradus, and the Nebula about eta Argus. MNRAS, 36, 69.

Published comments

Photo index

Photo Index by Jim Lucyk: Astronomy mag. 2/86 p102, Burnhams V1 p469, 470, Ast.Obj.for South.Tel. (Hartung, 1984), Sky&Tel. 4/73 (centerfold), Sky&Tel. 4/79 p355, Sky&Tel. 4/81 p285, Sky&Tel. 4/84 p305, Sky&Tel. 6/70 p369, Sky&Tel. 6/76 p378, Sky&Tel. 7/77 p23, Sky&Tel. 10/83 p305, Astronomy mag. 6/75 p12, 13, Astronomy mag. 12/79 p70, Vehrenberg's Atlas of DS Splendors (3ed) p102, 103.

Bailey, S.I. (1908)

"!!! nebula, B, irregular, rich in *s; Great Nebula about eta Carinae, central portion"

Bailey, S.I. (1908) A catalogue of bright stars and nebulae. Ann.Harv.Coll.Obs., 60(8), 199.

Remarks, p.217: "The spectrum of the nebula surrounding eta Carinae is gaseous. this is one of the largest and finest of the nebulae. the whole region is also very rich in stars."

Innes, R.T.A. (1914)

Innes, R.T.A. (1914) The magnitude of Eta Argus, 1914, and discovery of a close companion to it. MNRAS, 74(8), 697-698.

Innes, R.T.A. (1914)

Region around Eta Argo. Union Obs. Circ., No 18, 123-125.

[1914CiUO...18..123I]

Doig, P. (1925)

Journal BAA, 36(3), Dec, p91

Great nebula occupying a psace in the sky about 5 times the area of the Moon. Russell (Sydney) described it as 'a very fine speciment of a nebulous cluster with a central condensation associated with dark strucvtures and radiating streams of stars ... in most cases accompanied by narrow black channels in the general nebulosity which run parallel to and alongside of the star streams.' Sir John Herschel had also earlier pointed to the distubution of the involved stars alng the edges of the dark spaces in the nebula. The star Eta Argus is situated on the eastern border of the 'Keyhole' marking. A trident-shaped or swan-like luminous part south of eta, which appears to have been very bright and conspicuous about 1834-8 when Sir John Herschel executed a careful drawing of the nebula, had disappeared or become very faint by 1871 when Russell could not see it wiht the 11-inch Sydney refractor. A comparison of Herschel's drawing and modernhotos show substantial agreement but for this particular feature; and it seems possible that its disappearance or (more probably) fading may be associated with the change in the light of eta from about 1st mag to 7th mag.

Doig, P. (1925)

Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part III. Southern Objects. M.N.R.A.S., 36(3), 91.

Doig, P. (1926)

Doig, P. (1926) "A Catalogue of Estimated Parallaxes of 112 Nebulae, Open clusters and Star Groups", Vol 36 (4), p 107-115.

"nova with nebulous stars and bright and dark nebulosity."

Bok, B.J. (1932)

Bok, B.J. (1932) A study of the eta Carinae region. Harvard Reprint 77. [original reprint]

Shapley, H. & Paraskevopoulos, J.S. (1940)

Galactic and Extragalactic Studies, III. Photographs of thirty southern nebulae and clusters. Proc. N.A.S., 26, 31-36.

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

Ced 109a (NGC 3372)

Position (1900): RA 10 41.2, Dec - 59 8

Star: Cl (Mp=5.0:, SpT=O, B)

Spectrum of nebula: emission spectrum (observed)

Classification: Nebulous cluster (Nebulous envelop of intricate structure, eg. NGC 2175)

Size: 120'x120'

Notes: "Ced 109 The {eta} Carinae region. Ced 109 a = NGC 3372 = GC 2197 = h 3295 = Dunlop 309 = Lacaille III 6. Disc. 1755.(30, 122, 123, 174, 175, 177, 191, 194, 216, 228, 365, 366, 382, 482, 486, 520, 560, 561, 575, 635, 636, 666, 682). R. This is the "Key-hole nebula". See further Bok's monograph (123)."

Thackeray, A.D. (1949)

Thackeray, A. D. (1949) "Nebulosity surrounding Eta Carinae" No. 848, February, p 31-33.

(Radcliffe Observatory, Pretoria. 1948 September 26)

The star eta Carinae is doubly renowned for its prominent position in Herschel's 'Keyhole Nebula' [Bok. A Study pf the Eta Carinae Region, Groningen, 1932; Harvard Reprint 77] and for its peculiar variability like an extremely slow nova which was one of the brightest stars in the sky from 1843 to 1856. Today it is still about the 8th magnitude, having shown littel change in the past 50 years ... This note describes preliminary obervations of th region in July 1948 with the newly-installed 74-inch reflector of the Radcliffe Observatory, Pretoria; since that date that star has been too low for useful observation.

Visual observation at the Newtonian focus with a power of 360 or less rewards the observer with a magnificent spectacle. The general nebular backgropund has the blsuih-green tinge characteristic of the Orion type, doubtless due to the 'nebulium' lines. But in the immediate neighburhood of the star, and extending 5'' of arc either side of it in position angles 130� and 310� there is a brilliant nebulous mass with a strong red tinge (believed to be mainly due to H-alpha) in the form of a truncated wedge; it has been not unfairly described as like a 'red spade-beard'. The narrow end of the wedge (p.a. 310�) brightens near the rim and thus appears like a portion of a shell about 1''.5 wide. The broad end (about 4''.5 wide) shows a similar brightening but at its sides, not at the exterior rim; these sides have approximate position angles 105� and 145�. This inner portion shows well on a 5-second exposure on Ilford Rapid Process Panchromatic plates without filter, and the brightening in pa 105� and 145� is distinct on a 10-second exposure on Ilford Astra VIII through Wratten filer 25 which transmits H-alpha. The measures quoted were made from the photographs.

The accompanying composite sketch is taken from these and other photographs extendign up to a 3-minute exposure on Ilford HP3. The outlines of the various nebulosities and star images were traced out from projected images of the original negatives enlarged 30 times and it is thus possible to reproduce on a singel diagram muc more detail, covering a iwde range of density, than can be seen on any one photograph. With increasing exposure, the inner 'spade beard' nebula diffuses out into a patch about 50% larger elongated in the same direction; this is shown in the diagram by a dashed curve. Then comes a rapid falling off in intensity.Farther out appears an elliptical shell again elongated in the same general direction (130� and 310�). This has two pronounced condensations of brightening (pa 150� and 240�); although the nuclei of these do not lie far from the strong diffraction rays from the central star (caused by the supports of the Newtonian mirror) their reality is rendered extremely probable by the extension of the second, and brighter, from pa 225� to 270�. This second shell cannot be traced on available photographs between pa 330�, where it is farthest from Eta (17'') and 30�, where it is nearest (''). Near each of these two extremeties appears a faint condensation which may be stellar. This outer shell has not been seen visually.

Measures of stellar components of eta Carinae have been made ..."

+ sketch.

Hoffleit, D. (1953)

1953AnHar.119...37H

A Preliminary Survey of Nebulosities and Associated B-Stars in Carina.

Sher, D. (1965)

Sher, D. (1965?) Structure of the Milky Way in Carina. Q.J.R.A.S., 6(3/4), 299.

p 308: "NGC 3372 etc. NGC 3372 is a large emission region and strong discrete thermal radio source with an apparent diameter of about 2 degrees. Several slucetrs of stars are seen against the nebula and at least one of them, Tr16, is known to contain O stars ... The distance of NGC 3372 has been estiamted many times over the years. B J Bok studied the preferential concentration of early type stars in the direction of the nebula at various distances and found this to be most marked at 1.1kpc which he then assumed to be the distance of the nebula as well. Becker and his group have found distances of 1.66kpc and 1.50kpc for the three clusters Tr14, 15 and 16 - all seen against the nebula - by measn of a conventional three-colour photographic photometry ..

The star eta Carinae - an erratic variable of great amplitude - appears to lie within NGC 3372 in the cluster Tr 16, and, consquently, NGC 3372 has often been called the 'Eta Carinae nebula'. The discovery of a small grouping of 'nebulae' within 10 arcsec of eta Carinae rather confuses the nomenclature, but references to either nebula are usually easily separated by their context. ...

Certainly there is nothing in the results obtaind so far to suggest that eta Carinae is not itself at the same distance as the nebula NGC 3372 and the associated clusters and early type stars, but this is all that can be said at present."

Sulentic & Tifft (1973)

(Sulentic and Tifft 1973) notes that this is a diffuse nebula.

Malin, D. (1987)

Malin, D. (1987) The splendor of eta Carinae. Sky&Telescope, Jan, 14.

Smith, N. et al. (2003)

Mass and kinetic energy of the Homunculus Nebula around eta Carinae. AJ, 125, 1458-1466.

[2003AJ....125.1458S]

"We examine thermal infrared images of eta Car at wavelengths from 4.8 to 25 microm. obtained with the MIRAC3 camera system at the Magellan Observatory, and we conclude that eta Car's circumstellar Homunculus Nebula contains much more mass (> about 12 M_solar) and kinetic energy (10E49.6 - 10E50 ergs) than had previously been recognized. � our images suggest ... that roughly 10 M_solar or more resides ... in the rapidly expanding polar lobes of the Homunculus, know to be ejected during eta Car's "Great Eruption" in the 19th century."

Section 5. Implications for the Great Eruption.

"The analysis above indicates that the Homunculus contains roughly 0.125 M_solar of dust. With a conservative estimate of the gas-to-dust ratio of approx 100 (it could be a factor of 2 higher) we estimate that the total mass contained in the Homunculus is at least 12.5 M_solar. Some of this mass may be located in the putative equatorial torus. We have shown that the bright clumps in the torus are warm, and they contribute a small fraction to the total mass, but some cooler material may still be shielded and hidden in the equatorial debris. � it may be possible that 10%-20% of the total mass in the Homunculus may be hidden in the equatorial torus or in the low-latitude regions of the side walls of the polar lobes (as much as 2.5 M_solar). Therefore it is likely that at least 10 M_solar of material resides in the thick caps of the polar lobes.

"This previously unrecognized large mass of material in the polar lobes places valuable constraints on the physics of the Great Eruption, because we know from proper motion measurements that the polar lobes were ejected during that event. There are important consequences for two fundamental parameters of the eruption:

"1. The mass-loss rate. � If the Great Eruption lasted about 20 yr, then the time-average mass-loss rate during the event was > about 0.5 M_solar per year (it could have been as high as 1 M_solar per year since our assumed gas-to-dust ratio is conservative). This is higher than the value of about 0.1 M_solar per year that is usually quoted. Most of the mass loss was directed toward the poles, which poses an interesting theoretical question beyond the scope of this paper. �

"2. The kinetic energy in the ejecta. � The polar lobes are expanding at roughly 650 km/s, given their projected size in images and the age of the Homunculus. With a large mass of greater than about 10 M_solar, the polar lobes also carry a great deal of kinetic energy. The mechanical energy imparted to the ejecta during the Great Eruption was therefore on the order of 10E49.6 - 10E50 ergs, much higher than previously assumed. The mechanical energy in the expanding Homunculus is greater than the total amount of luminous energy presumed to be radiated by eta Car during the 20 yr duration of the Great Eruption event, which was approx 10E49.5 ergs."

The authors note that for eta Carinae's present-day wind, the ratio of wind momentum to the photon momentum ("performance number") is comparable to that found in the powerful radiatively driven winds of Wolf-Rayet stars. However, "for conditions during eta Car's Great Eruption we find the performance number > 1000. Performance numbers as high as 10 can result from purely line-driven winds but such extremely efficient momentum transfer with performance number = 1000 is unlikely� Perhaps some of eta Car's luminous output during the eruption is unaccounted for, but it is hard to accept that it has been underestimated by a factor of 10. Thus, rather than a transfer of momentum by radiation pressure in a wind, the high value of the performance number implies a more direct transfer of energy in an explosion (or perhaps pulsation-driven mass loss). For comparison, performance numbers near 1000 are typical for Type II supernovae. (Zwicky's 1964 description of the Great Eruption as a 'Type V supernova' may have been somewhat appropriate after all, even though eta Car survived its outburst.) In any case, the new estimated mass and kinetic energy of the Homunculus indicate that the Great Eruption was more powerful than is usually assumed. In fact, the energy quoted here is an underestimate, since we have not included kinetic energy of additional fast-moving ejecta outside the Homunculus, some of which originated in the same event. It is intriguing that the underlying cause of such a powerful event remains unknown, despite detailed observational study and more recently examples of similar extragalactic eruptions."

Walter, R., Farnier, C. and Leyder, J.-C. (2010)

arXiv: 1008.2533v1

Located at a distance of 2.3 kpc, eta Carinae is one of the most massive (80�120 M_solar) and brightest stellar system in the Galaxy and features the strongest mass loss rate known. As, in addition, its colliding wind region is relatively wide, eta Carinae is a primary candidate for gamma-ray detection.

The 'Great Eruption' of 1843 saw eta Carinae become the second-brightest object in the sky; it was followed by another noteworthy flare in 1890. The Homunculus is the name given to the extended bipolar nebula observed around eta Carinae: it was crafted by the colossal amount of matter (10�20 M_solar) that was ejected during the Great Eruption. The second burst led to the ejection of approx. 1 M_solar, creating the so-called little homunculus. eta Carinae keeps emitting matter thanks to its powerful stellar winds: the mass-loss rate is believed to be 0.0001 to 0.001 M_solar per year.

Even if not all questions are settled, strong evidence suggests that eta Carinae is a binary system. For instance, radio, millimeter, optical, near-infrared and X-ray observations, obtained over the last decades, have unveiled the existence of a period of approx. 2022.7 +/- 1.3 days.

The first component in the binary system is very likely a luminous blue variable (LBV). The second component is probably a late-type nitrogen-rich O or Wolf-Rayet (WR) star. The semi-major axis of the orbit is 16.64 AU and the eccentricity is very high (e approx 0.9). Thus, the periastron distance is around 1.66 AU, while the primary star's radius, although poorly constrained, is estimated between 0.7�1 AU.

The X-ray emission of eta Carinae can be discriminated into two components, precisely known thanks to Chandra observations. The softer part prevails in the spectrum up to 1.5 ke V. It is spatially extended, and is likely linked to the stellar winds colliding with the interstellar matter. The harder part ... dominates over the 2-10 ke V domain. It is punctual, centered on the binary system, and believed to be due to the hydrodynamical shock created by the stellar winds of both components colliding with each other.

The X-ray spectrum of eta Carinae supports the colliding-wind binary scenario. The basic idea is that the LBV emits a rather slow and dense stellar wind (v approx. 500 km/s, M approx 0.00025 M_solar/year), which collides into the faster, shallower wind originating from the secondary component (v approx. 3000 km/s, M approx 0.00001 M_solar/year). In this framework, the wind collision region represents the location of the hydrodynamical shock, and thus of the X-ray emitting region.

Groh, J.H. et al. (2010)

Detection of high-velocity material from the wind-wind collision zone of eta Carinae across the 2009.0 periastron passage. A&A, 517, A9.

"Eta Carinae offers a unique opportunity to study the evolution of the most massive stars and their violent, giant outbursts during the luminous blue variable (LBV) phase. Eta Car is located at a distance of 2.3 +/- 0.1 kpc in the Trumpler 16 OB cluster in Carina and consists of a very luminous central object (L >= 5,000,000 L_solar) enshrouded in massive eject of approx. 12�20 M_solar (the Homunculus nebula)."

"The optical and near-infrared spectra of Eta Car exhibit low-ionization permitted and forbidden lines mainly of HI, FeII, NII, [FeII], and [NiII]. Since 1994, high-ionization forbidden lines, such as [FeIII], [ArIII] and [NeIII], have been detected in optical spectra of Eta Car. High-spatial resolution imaging and spectroscopy of the low- and high-ionization forbidden lines arise in the ejecta, in condensations known as the Weigelt blobs. At some epochs, the high-ionization forbidden lines were found to become weaker and eventually vanish [a spectroscopic event], and then recover their normal strength after several months [the spectroscopic cycle]. �

"Extensive monitoring of the optical spectrum of Eta Car showed that the spectroscopic events repeat periodically every 5.54 yr. This led to the suggestion that Eta Car is a binary system (Damineli et al. 1997) consisting of two very massive stars, Eta Car A (primary) and Eta Car B (secondary), amounting to at least 110 M_solar. The spectroscopic events are related to the periastron passage of Eta Car B, and the binary scenario is supported by numerous multiwavelength observations from X-ray, ultraviolet, optical, near-infrared, and radio wavelengths. Although most orbital parameters of Eta Car are uncertain, the wealth of multiwavelength works mentioned above are consistent with a high eccentricity (e approx 0.9) and an orbital period of 2022.7 +/- 1.3 d.

"Significant advancement in obtaining the properties of Eta Car A has been achieved, confirming that it is an LBV star with a high mass-loss rate (2.5 E-4 to E-3 M_solar/year) and a wind terminal velocity in the range 500 to 600 km/s. � A significant amount of material moving faster than 3000 km/s was discovered (Smith 2008) in distant ejecta far from the Homunculus nebula, which is understood to be related to the Giant Eruption and not (at least directly) to Eta Car B.

"Little is known about Eta Car B, since it has never been observed directly. The role of Eta Car B in the giant outbursts and on the long-term evolution of Eta Car A is not yet understood. Earlier analysis of the ionization of the ejecta around Eta Car have inferred an O-type or WR nature for Eta Car B. �

"X-ray observations require that Eta Car B must have a wind terminal velocity on the order of 3000 km/s. X-ray studies have also shown that a strong and variable wind-wind collision zone is present between Eta Car A and Eta Car B. �

The authors analyze spectroscopic measurements and "suggest that our observations provide direct detection of shocked, high-velocity [approx 1900km/s] material flowing from the wind-wind collision zone around the binary system" during the 2009.0 periastron passage.

Modern observations

Hartung, E.J. (1968) Astron.Obj.South.Tel

Hartung writes: "Eta Carinae with its associated star clusters and the great diffuse gaseous nebula enveloping it form one of the finest telescopic objects; on a clear dark night the region is beautiful beyond description, even for small apertures. The nebula is diversified by prominent dark lanes which indicate absorbing matter and it extends in irregular luminous clouds far beyond a large field. The bright orange Eta is surrounded by an orange red nebula about 3 arcsec wide, just visible with a 4-inch, and the spectrum of the star shows numerous bands with the red hydrogen-alpha shining like a tiny lamp at one end; this too can just be seen with a four-inch."

Burnham's Celestial Handbook (1978)

Burnham summarizes the object as "remarkable, bright, extremely large, irregular, with dark lanes, diameter 80' x 85'. Keyhole nebula, contains nova-like Eta Carinae."

Burnham writes that the star "Eta Carinae is located in one of the most splendid regions of the southern Milky Way, the great diffuse nebuloisty NGC 3372, often called the 'Keyhole Nebula', remarkable both for its great size and the complexity of its structure ... dark lines divide the nebulosity into several separate islands of glowing light; the brightest of these contains an irregular dark elongated mass - the keyhole itself - from which the nebula derives its name. In addition to this nebulosity, which forms a brilliant setting for Eta Carinae, the star itself is surrounded by a much smaller nebulous shell which is expanding at a rate of about four arcseconds per century ... bright nebulous condensations in the shell were detected visually by R.T. Innes in 1914, and were at first recorded as faint 'companion stars'. "

Sanford (1989) Observing the Constellations

Sanford says "the whole area is a delight to the visual observer, and each increase in telescopic aperture is rewarded by more fascinating detail."

Harrington, Phil

Harrington calls it "among the most amazing objects in the entire sky. Visible to the unaided eye, this huge glowing cloud is exquisite even in the most modest optical equipment. Dark rifts divide the nebula into several distinct regions, with the most prominent patch clearly teardrop shape. Entombed within this cloud is Eta Carinae itself, a dazzlingly orange star with an unusual past ... closely surrounding Eta Carinae is a tiny reddish glow measuring only 3 arc seconds wide. This diminutive cloud may be seen through moderate-size instruments at high magnifications. For a good over-view of the entire network of nebulosity, use your lowest-power widest-angle eyepiece. Even then, NGC 3372 will more than fill the field."

Tsang, Simon

Simon Tsang writes that "the nebula is segmented by prominent dark lanes and has a darker patch, the Keyhole, just west of the star Eta. With its beautiful swirling outer extensions, this is without doubt the most splendid emission nebula I've ever seen."

[deepsky] daveafna@hotmail.com

From: daveafna@hotmail.com

Date: 17 March 1999

Time: 12-30 am

Location: Randburg, South Africa

Equipment: 10" SCT, 15 mm, 25mm

Seeing: ANT II - slight undulations, with moments of calm lasting several seconds

Object: Eta Carina Nebula, RA 10hr 45min,

Dec -59, 41

I spent the best part of an hour observing the Eta Carina Complex. It's a jumble of nebulae, clusters and bright stars seen in perspective along the Carina spiral arm of our galaxy. The most striking features of the nebula are the three broad dust lanes forming a Y-shape.

Most of the stars in the nebula lie at about 6800 light years distant. Eta Carina itself is the brightest star in the centre, among a group of white O-stars. It lies adjacent to a dark patch known as the Keyhole. Dark dust lanes hide the nebula beyond parts of the Keyhole. The blue tinge is as a result of reflection from the dust cloud, near the keyhole, from the light of Eta Carina itself.

When Sir John Herschel pictured the Eta Carina Nebula around 1834-8, he drew the Keyhole much more definitely than it appears today indicating that this part of the nebula has faded away. This is understandable as Eta Carina itself has faded!

Bayer, in 1677, perceived Eta Carina as the seventh brightest star in the constellation. In 1843 it became the brightest star after Sirius at mag -1, but gradually faded to mag 7 or 8. In recent years, its variable nature has brought it to mag 6.2. There has been renewed interest in this highly unstable variable since the stunning pictures taken by the Hubble Telescope.

Last night was a particularly exciting observation because I could resolve the decidedly non-stellar shape of Eta Carina. It is a red-orange oval shape, described by Innes 70 years ago as having the shape of a little fat man with stubby arms and legs; the little nebula is called the Homunculus (or manikin). The Homunculus is expanding at high speed - about 500 km/s.

I could not see it last night, but David Thackeray discovered a fainter patchy outer ellipse of nebulosity in 1948, while he was testing the newly installed Radcliffe 74 inch telescope in South Africa.

At infrared wavelengths, Eta Carina is the brightest star in the sky. Optical energy is being soaked up by the nebula and re-emitted as infrared radiation.

The instabilities of Eta Carina have caused it to shrug off two or more shells, each an attempt to reduce its mass and become stable. If, as seems likely, it cannot achieve this end, Eta Carina may explode soon as a supernova, one of the greatest explosions mankind will ever witness.

Gross, Todd (IAAC)

Observer: Todd Gross; Your skill: Intermediate ; Date and UT of observation: 1/1/98 10:45 GMT; Location & latitude: Cancun, Mexico; Site classification: Urban/Suburban; Limiting magnitude (visual): 5.1 zenith (est) 3.5 (est) in vicinity of object; Seeing (1 to 10 - worst-best): unknown - 5?; Moon up (phase?): No; Weather: Clear to pt. cloudy; Instrument: 80mm APO refractor f/6 - f/l 480mm; Magnifications: 16x,32x,69x; Filters used: UHC

Fairly large and easy to find in 8x32 binoculars, but mistook for NGC3532 for awhile until checking in scope. Hint of nebulosity in binoculars and telescope wtih the UHC filter but... With the UHC filter I found it to be a very large elongated streak of nebulosity split in two parts N and S. However, I was not seeing it as it is depicted in photos, I was not taking in it's full extent, probably because it was so low in the sky, only around 10-15 degrees up, in the haze and local light pollution. Nebula was most pronounced in the north part, with a very obvious dark lane running up from the south, and others criss-crossing e-w noticeable with averted vision. A bit larger, but not as impressive as M42 in these conditions. There was a loose foreground cluster involved coincidentally.

Coe, Steve (IAAC)

Observer: Steve Coe; Your skills: Advanced (many years); Date/time of observation: 25 Feb 1998; Location of site: S.S. Dawn Princess (Lat +12, Elev 0); Site classification: Suburban; Sky darkness: 5/10 1-10 Scale (10 best); Seeing: 4 1-10 Seeing Scale (10 best); Moon presence: None - moon not in sky; Instrument: 10X50 binoculars, Pentax, no tripod; Magnification: 10X

While sailing to a position to observe the total solar eclipse, I observed several deep sky objects from the deck of the Dawn Princess. The seas were calm, but the ship was travelling at about 20 knots (28 mph) to get to the next port of Aruba, so I had to battle the wind. But, it was worth it! Bracing my elbows on the rail of the ship helped and managed some good binocular observations.

Eta Carina is immediately obvious naked eye as an elongated bright spot in the Southern Milky Way. In the 10X50s it is over one degree in size with averted vision and is much brighter in the middle. There are 14 stars involved within the nebulosity. There is an obvious dark lane that forms a "V" shaped through the nebula with the brightest nebulosity and the star Eta Carina both to the the north side of this dark lane. Averted vision makes the nebula grow significantly in size. The field of view is stunning, a rich Milky Way field with this large, bright nebula dead center is unique.

Murrell, Andrew (IAAC)

(IAAC) Obj: The Homunculus - Inst: 20" f5 Dobsonian

From: Andrew Murrell (hector@dragon.net.au) Observer: Andrew Murrell Your skills: Advanced (many years) Date/time of observation: Location of site: Ilford NSW Australia (Lat , Elev ) Site classification: Rural Sky darkness: 6.5 1-10 Scale (10 best) Seeing: 8-9.5 1-10 Seeing Scale (10 best) Moon presence: None - moon not in sky Instrument: 20" f5 Dobsonian Magnification: 160-700 Filter(s): none Object(s): The Homunculus Category: Planetary nebula. Emission nebula. Class: stellar ejecta Constellation: carina Data: mag 6.5 size 30" Position: RA 10:45.1 DEC -59:41

Description: The Homunculus is the small nebulae that surrounds Eta Carina. It is the envelope of stellar material that was ejected from the star about a century ago. This is the only nebulae that shows an obvious colour, Bright orange. This colour is very striking against the star background. The initial observation was at 160x. This shows the surrounding keyhole nebulae NGC3372, which defies description. The Homunculus appears as a peanut shaped orange blob about 30" across. At 300x it appears as a bright hazy star with a lobe or bubble of material on either side, orietated SW-NE. The lobe to the SW is the brightest, and appears granular with a dark lane running throughthe middle which curls to the southat the end. The NE lobe is fainter and shows no internal detail The center star is about 6.5 magnitude and has a jet progecting to the north about 5" long. Averted vision at this power intensifies the colour and shows a bright knot 5" WSW of the star in the SW lobe. By increasing the magnifaction to 720x even more detail was glimpsed. In moments of perfect seeing the granulation in the NE lobe became apparent. The bright knot became visible with direct vision,and the colour remained. The dark lane seen before in the SW lobe lost some of its structure, looking more difuse and ending in a small dark hole positioned about 5" from the southern edge of the nebulae. The higher magnifaction increased the contrast. The edge of the nebulae remained sharp across the entire perimeter and the arm or jet was easily picked up. What became most noticable about the homunculus was the FAINT halo that surrounded the entire object and doubled its size. The difuse glow had an indistinct edge and appeared evenly distributed about the object. No intermal details were seen in this faint envelope A right angle of 15th magnitude stars are positioned about 15" NW of the central star adding to the view at this power. As a side note to this observation stars of 4th magnitude and brighter had difraction rings visible, one complete ring and two partial. The seeing was the best in several years that I had seen Reducing the magnifaction to 300x I looked for the faint halo but it would not reveal itself, probably due to the glare from the star and the nebulae. This goes down as one of the TOP 5 objects in the entire sky.

[amastro] observing the homunculus April 16th

Observing done at the ASNSWI site at Ilford in NSW Australia.

The Homunculus is the small nebulae that surrounds Eta Carina. It is the envelope of stellar material that was ejected from the star about a century ago. This is the only nebulae that shows an obvious colour, Bright orange. This colour is very striking against the star background. The initial observation was performed at 160x. This shows the surrounding keyhole nebulae NGC3372, which defies description.

The Homunculus appears as a peanut shaped orange blob about 30" across. At 300x it appears as a bright hazy star with a lobe or bubble of material on either side, orietated SW-NE. The lobe to the SW is the brightest, and appears granular. A dark lane runs through the middle of this lobe which curls to the south at the end. The NE lobe is fainter and shows no internal detail

The center star is about 6.5 magnitude and has a jet projecting to the north about 5" long. Averted vision at this power intensifies the colour and shows a bright knot 5" WSW of the star in the SW lobe. By increasing the magnification to 720x even more detail was glimpsed. In moments of perfect seeing the granulation in the NE lobe became apparent. The bright knot became visible with direct vision, the colour remained. The dark lane seen before in the SW lobe lost some of its structure, looking more diffuse and ending in a small dark hole positioned about 5" from the southern edge of the nebulae. The higher magnification increased the contrast. The edge of the nebulae remained sharp across the entire perimeter and the arm or jet was easily picked up.

What was most noticeable about the homunculus was the FAINT halo that surrounded the entire object and doubled its size. The diffuse glow had an indistinct edge and appeared evenly distributed about the object. No internal structure was seen in this faint envelope.

A right angle of 15th magnitude stars are positioned about 15" NW of the central star adding to the view at this power. As a side note to this observation stars of 4th magnitude and brighter had diffraction rings visible, one complete ring and two partial. The seeing was the best in several years that I had seen.

Reducing the magnification to 300x I looked for the faint halo but it would not reveal itself, probably due to the glare from the star and the nebulae.

This goes down as one of the TOP 5 objects in the entire sky.

Clear skies, Andrew Murrell

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At 01:51 AM 11/26/99 -0800, Andrew Murrell wrote:

]The Homunculus is the small nebulae that surrounds Eta Carina.

]This goes down as one of the TOP 5 objects in the entire sky.

Agreed. And two other Top 5 objects in the entire sky are 47 Tucanae and the Tarantula Nebula. Anybody on this list who hasn't made a trip south of the equator should be planning one.

Tom Polakis

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]Agreed. And two other Top 5 objects in the entire sky are 47 Tucanae and

]the Tarantula Nebula. Anybody on this list who hasn't made a trip south of

]the equator should be planning one.

]

]Tom

]

Although these are great objects, nothing prepared me for the shock of seeing the summer Milky Way stretched overhead. In 1993, I spent 3 weeks on a trip to the Pilbara region gathering +2.5 gyr black shale and banded iron formations (BIF) for several related research projects. Due to travel / logistical problems I brought a pair of 7 x 50's and a 4 1/4 -inch Astroscan. Even with these small instruments, I was able to log over 200 objects, including dozens in the LMC and SMC. But by far the most majestic sight was the great vault of the Milky Way, with the Sagittarius/Scorpius area directly overhead.

And yes, the Milky Way does cast a very low contrast shadow.

- Rich

P.S. I believe kangaroos are among the dumbest animals on Earth, or at least they love playing tag with 'roadtrains' . I must have spotted hundreds their carcasses lining the 700 km trip I took along the Great Northern Hwy. In contrast, no Emus lined the roadway nor that many lizards or snakes.

------------------------------------------------------------------------

I agree with Tom and Richard. 47 Tucanae is a fantastic site through any telescope. Hector (my 20" f5) at low power shows a distinct golden colour. I have heard of other people describing the cluster as pale pink. I have even had one person fall off the ladder at the shock of the site of the cluster.

The Tarantula lives up to its name as at low power as it looks like a spider with its leg spread. It shows a very pale green through hector. On nights of good seeing I enjoy observing the nebulae at 700 mag. The nebulae has sharply defined edges and a fantastic cluster in the center The Milky Way on the rise during March is a wonderful site as you can watch the Emu walking on the horizon. The dark lanes in the Milky Way from the Coal Sack to Sagittarius when viewed as a whole look like a giant Emu. The head of the animal is the coal sack with the star in dark nebulae positioned where the eye would be. the neck is the thin run of dark nebulae that starts at the pointers with the body filling out through Scorpio and Sagittarius. I find that it casts a noticeable shadow when the galactic center is positioned overhead.

The Homunculus is only the nebulae that surrounds the star Eta Carina. The entire nebulae complex surrounding the star is also one of the wonders of the southern sky as well. NGC3372 is enormous covering several fields through Hector. It appears pale green and is very bright.

If you haven't been down under I extend an open invitation. The ASNSWI (my astronomical society) has an observing site 3 hr dive north west of Sydney with fantastic skies. Several members own large scopes who will happily observe with you and show you what is on offer. We even have a 17.5" club scope open for general observing. Comfortable accommodation is easily available with 4 small dorm cabins and a house on site. Staying in Sydney is no problem either as many of the club members house overseas visitors regularly. I would be happy to have some observing companions..

Clear skies

Andrew Murrell

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Could I also put in a bid for NGC 6752, the globular cluster in Pavo as one of the best objects in the southern sky? In my opinion it ranks number 3 after omega Cen and 47 Tuc.

Steve

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And let us not forget Omega Centauri.

Dave Mitsky

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Dont forget the Galaxies NGC253, NGC5128, NGC1365, The LMC and the SMC. I believe these last two are the best site in the sky to the naked eye. Also on globulars, NGC2808 as a wonderful cluster.

Clear skies

Andrew Murrell

Brian Skiff

QBS: sm dk patch 17' N/sl W of w Carinae is ~5'x2' elong closely N-S.

Curtis Schmidt plate (5-min exposure on IIIa-J under Full Moon)

15cm - let's start by comparing M42 with eta Carinae nebula @ 50x, since both are at nearly the same altitude right now. No comparison---they're a study in contrasts! Orion Nebula has comparatively small area of hisfcbr and smooth texture centered on Trapezium. There are hardly any bkgrnd *s as a consequence of the assoc dk cloud out of which the *s are forming. eta Car is much more extensive (~2 deg diam) and is of generally lower sfcbr, but far more intricate. The most striking difference @ 50x is that eta Car is set against a bkgrnd of m12-14 *s that must represent the densest Milky Way bkgrnd in the sky---evident since it is also the very brtst region in the sky to the eye as well. Later same night: because of size 30x best; it overflows 1.6-deg fld. [OIII] filter def reduces brtness of neb even though contrast is up; UHC much better for general viewing. brtst section is triangular wedge N of center of neb that overlies oc Tr 14 & 16. a mod well-defined arm on the W side extends 40' NW to the m6 orange * nr oc Bo 10. the border of this arm facing SW is vsharply def and forms an edge of a parallel dk lane leading NW out of the neb. this triangular wedge is brtst btwn Tr 14 & 16 and fades generally NNEwd. just W of Tr 16 & eta Carinae is the N-S feature called the Keyhole. this is nrly black SW of eta Carinae and is filled in Nwd, but retains a well-def border. this feature is small enough that 80x is better, and it is generally improved by the UHC. a plume of vbr neb arcs Ewd from the E edge of this feature across the N side of Tr 16. general mottling of this lg triangular wedge of neb is better shown @ 80x than at lower powers.

the neb S of this triangle is sep by a vdistinct pair of dk lanes, one alluded to above. the lane heading NW is sharply bounded and has nrly straight edges that are wedged at a sl angle. the one NE is wkr and w/o sharp borders. the stuff extending S hangs like a beard below this wedge of a smile. it is generally fntr and more ill-def than the Nrn part, but sev distinct features appear:

going from W to E, first there are three streamers hanging Swd from the edge of the dk lane going NW. the Wmost of these is pretty f w/o UHC, but is vis @ 30x. these start heading SW then curve S, ending ~45' S of eta Car near w Carinae. NW of w Car is a vdk patch elong NNE-SSW, vconsp w/averted vis. btwn w Car and eta Car is a much longer but less dk streak that reaches nrly to vertex of dk lanes N. another brtr patch of neb appears on the SE side of this region. much mottling @ 80x and all features (even dk ones) enhanced by UHC. 30x shows isolated oval emission patches 1.5 deg N and NE of eta Car.

general scanning for *ry stuff: lots of broad clumps w/in +/-1.5 deg of eta Car, but nothing sharply delineated like a cl; mostly just abs holes. 50' S/sl W of eta Car is orange m5 *, w Car. BS, 22Feb1990, LCO.

Ed Finlay

1993 May 31

ASSA DSOS: Ed Finlay, observing with a Meade 4-inch ED APO refractor from Johannesburg, 1993 May 31, notes "a spectacular sight; stars, clusters, dust lanes, light and dark nebulae."

Contemporary observations

Auke Slotegraaf

2009 February 27/28

Sutherland (Huis Lana)

"Bertha" 12-inch f/4.8 Dobsonian (EP: 32mm, 25mm, 10mm, 6.3mm Plossls, 2x Barlow, 32mm Erfle)

Conditions: Clear, dark.

Just before packing up, I took a look at eta Car and the Homunculus. The seeing was very good with crisp, steady, images. The south-eastern lobe is, as usual, brighter and larger than the north-western one. However, the NW lobe appeared larger than I have seen it before, and the dark marking on the SE lobe was more distinct. As noted on 2009 Jan 23/24, the SE lobe has a little bulge, immediately SW of eta Car. But more intriguingly, it was very clear that the NW lobe is not a regular petal-shape as seen on all previous occasions. Now, I see a prominent gap in its outline, north of eta, creating a short jet or tendril of orange nebulosity, quite apart from the main lobe. This gap/tendril was repeatedly seen through several eyepiece changes. Previously, it seemed as if there was just a slight marking on the NW lobe (a less obvious version of the dark mark on the SE lobe), but tonight the impression of a gap is very strong.

2009 January 23

Sutherland (Huis Lana)

"Bertha" 12-inch f/4.8 Dobsonian (EP: 32mm, 25mm, 10mm, 6.3mm Plossls, 2x Barlow, 32mm Erfle)

Conditions: Clear, dark.

It goes without saying (he says) that eta Carinae is regularly visited. The region is, of course, awesome. The orange star eta Car itself has two lobes like little bits of skin sloughed off it. The western lobe is distinctly brighter and larger than the eastern one, but both shine with a soft orange light. The larger lobe is not regularly shaped (as previously seen) but has a secondary bulge, a little bump on the northern edge, nearest eta. Inside this lobe is an elongated dark marking so that it appears almost annular.

2009 January 01

Sutherland (Middelfontein)

8-inch f/6 Dobsonian

Conditions: Clear, dark.

Casually sweeping over the neighbourhood of the nebula is a jaw-dropping experience. Eta itself is a bright orange star, set in a field overflowing with intricate nebulosity, bright and dark. Scrutiny of the star itself shows something curious: it is distinctly elongated. Conditions were good so powers of up to 380x could be used to take a closer look. The star is centrally located in an oval nebula, oriented roughly northwest-southeast. The southern part of the nebula is clearly brighter, and very slightly larger, than the north-western part. Beginning at 120x I noticed that a fine dark line (~NE to SW) divides the oval nebula in two, centred on eta, creating the impression of two distinct lobes (or a cocktail sausage pinched in the centre, if you're peckish). Even a wide-field 75-power view shows the two-lobed nebula distinctly. On closer inspection, the main lobe is oriented to the east-southeast of eta (not southeast); the smaller lobe, at its base, is just 60% the width of the larger, and extends outward for only 75% of its larger cousin's distance. It thus appears narrower than seen at first. More significantly, I get the distinct impression that the two lobes are not oriented with their major axes parallel; the smaller lobe deviates ~20 degrees off the parallel, so that it lies more north-west than NNW. (The sketch should make all this clear!) The entire field is stuffed with mottled patches of light and dark (thank heavens for photography!) that certainly defies my ability to sketch.

2002 July 01

Stellenbosch (Paradyskloof Rifle Range)

11x80 tripod-mounted binoculars (12.5-mm aperture mask)

Conditions: Dark moon. Slight easterly breeze. NELM approx 5.5 at the pole. Dew.

Northern portion of Eta Carinae nebula: Better defined than the southern part. Elongated northwest-southeast, bright nebulosity surrounded by dark. The long southwestern edge and the short southeastern edge are sharply defined; to the northwest the nebula trails off into thin wisps. Binoculars show six stars arranged in an arch, or half-circle. Within the arch is a milky nebulosity, trailing off to the northwest. [rough sketch made in logbook] Southern portion of Eta Carinae nebula: QZ Car (as marked on U427) and another to the southwest are the two brightest stars in this part of the nebula; they appear as two widely separated stars surrounded by extensive nebulosity. Lacaille's description: Supported; though I'm not sure they are really "small stars". Will have to check on Lacaille's verbal magnitude scale.

1997 April 14

1997 April 14, 02:00 - 04:00 Jonkershoek. 11x80's tripod-mounted. A complex region of dark and bright nebulosity. Bright nebulosity split by multi-legged dark nebula.

1994 February 12

1994-02-12, Die Boord, 11x80's tripod mounted. The sketch below was made under conditions of very low contrast, onto a prepared star-tracing.

1992

This nebula is wonderful in 11x80 binoculars. Eta Carinae itself is prominent and easily visible as a slightly orange star within the textured nebulosity. The immediate impression of the nebula is of two brighter lobes of nebulosity divided by a dark rift. This rift branches dimly into a Y-shape east and south of Eta. The southern part of the nebulosity appears as an elongated, bright mass with large, fainter winglike extensions west and east. The northern half, containing Eta, appears mainly elongated to the north-west, away from Eta. The whole four degree field of view is filled with many, many stars. The background field is very rich with the unresolved haze of the rich Milky Way background. I get the impression that these stars are quite shy; as soon as you look away, they pop into view, but if you look at them, they vanish again. Look for the two bright orange stars in the field; w Carinae to the south and t2 Carinae to the north-west.

1991

A 10-inch f/5 at 30x shows this as a very complicated area of contrasting nebulosity and black sky; Eta itself appears slightly orange and is clearly bloated. The whole one degree eyepiece is filled with delicate textured wisps of this beautiful nebula.

Chris Vermeulen

2006 March 25

2006/3/25-26, 0h00-03h00

Sky Conditions: Poor: Cloudy

Quality of Observation: Moderate

Ngwenya Lodge

6" Dobsonian, 25mm & 10mm Eyepieces

NGC3372, or the Keyhole Nebula is a bright nebula in Carina. NGC3372 is surrounded by a magnitude of stars and the cloudiness of the nebula is quite clearly visible as with a high magnification it appears that the cloud is split in two by a dark cloud. On lower magnification the open cluster IC2602 (Southern Pleiades) is also visible in the field of view. The bright stars in NGC3372 cause the nebula to "glow" against the dark backdrop of the night sky, making the Keyhole Nebula a wonderful and exciting object to observe.

Carol Botha

2007 March 10

Date: 2007 03 10. 20:15

Location: Bellville

Instrument: 8-inch Dobsonian, 25mm eyepiece

Sky: Clear; light pollution

Notes: Bright nebulae with dark lanes inbetween. Bright orange star � one of a triangle form. I noticed that groups of stars formed curved lines.

Gary Lillis

2007 August 01

2007 August 01, 19:00 SAST

Walmer, Port Elizabeth

8x21 binoculars

Conditions: Clear, atmosphere stable, stars prominent.

eta Carinae Nebula. Large with softish appearance, averted vision reveals few prominent stars within nebula of M7 other than the bright eta Carinae. Nebula is 120arcmin with elongated oval body east to west and north to south, apparent magnitude M5. Brightness of wedges appears uniform M8, edges tend to be dimmer M8.5. North-south wedge is slightly dimmer than east-west wedge. Brighter area around eta Carinae running east-west within east western wedge could be Homunculus Nebula. Dark lane separates the two main wedges south of eta Carinae running east-west possibly Keyhole Nebula. NGC 3372 is surrounded by many field stars of M7-8 about one degree in each direction.

Richard Ford

2010 May,15 Saturday

Location:Perdeberg.

Instrument:12"Dobsonian Reflector Telescope.

Sky Conditions: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.

Limiting Magnitude:4.9.

First Impression:Nebula.

Location:Carina.

Time:7:52pm.

Chart Number:No.16(Extract taken out of "Atlas of the Night Sky").

Size:26mm Eyepiece:Field Of View:57'/2=28.5'. 20mm Eyepiece:Field Of View:50'/1.5=33.3'. 28.5'+33.3'=61.8'. 61.8'/2=30.9'. Size in Arc Minutes:30.9'.

Brightness:Extremely Bright.

Brightness Profile: High Surface Brightness.

Challenge Rating:It is a very breathtaking sight to observe this nebula in a very large telescope.

Description

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In some areas of this nebula,I have noticed areas of uneven brightness around the 1st to 3rd magnitude stars.This nebula is extremely bright with bright lanes of nebulosity where star formation is taking place.In this nebula,globules of gas and dust is formed where star formation is taking place.Towards the central outskirts of this nebula,a dark lane is observed known as the Keyhole Nebula,a dark patch in the center of the Eta Carina Nebula.This dark patch is barren of stars.The humunculus of this nebula is also observed in this nebula.The structure of the Eta Carina Nebula has a dramatic appearance of bright lanes of nebulosity.

Pierre de Villiers

2016 February 05, Friday

Location: Bonnievale SSP

Binoculars: Canon 12x36 IS

Sky conditions: Good (8.5/10)

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