Continuing from Part XII, in this installment we move a further two degrees south of NGC 2899, in a section on the eastern side of the 'False Cross'. First discussed is the easy to find NGC 2867, near the 2nd magnitude Iota Carinae. The two fainter planetaries follow this - He2-26 and He2-22, and further to the east is the faint planetary, IC 2501. For the surrounding fields, I have selected a few double stars, a pretty asterism and an eclipsing binary.

Doug's Note: Images of NGC 2867 (from HST) and IC 2501 are linked to this page. But since the additional planetaries of He2-22, He2-25, and He2-26 are quite stellar in appearance in the Skyview fields, their images are not linked here. IC 2501 is very much of a stellar object also, but since it is placed in a rather major catalog, I've decided to include it.  If you do want to view these fields, link here to Skyview, and at the appropiate form field, select Digitized Sky Survey, and enter the object's coordinates. He2-22: 09 15 08, -54 53 ; He2-25: 09 18 00, -54 39; He2-26(Sa2-41): 09 19 30, -59 12.

NGC 2867/ He2-27/ WRAY 16-43/ PK278-5.1 (09214-5819) has the advantage of being 1.2^O NNE of the bright 2nd magnitude star Iota Carinae, or alternatively 1^O SW of the 4.3 magnitude g Carinae. Contained in a densely packed starry field, and can be quickly found, by drawing an imaginary line between two field stars - a 9.5 and another 9.8 magnitude star. High magnification reveals a small aqua blue disk. I thought the colour was one of the most prominent and elegantly coloured of all the southern planetaries in this series. Considering that the measured B-V value is -0.5, this is understandable. (Note: As a comparison, Beta Centauri is -0.23) Few of the modern amateur references have little detail about this wonderful object. NGC 2867 has an interesting history as a deep-sky object - which is particularly unusual for a southern astronomical object.

John Herschel Discovery of the "Planetary Planetary".

John Herschel discovered NGC 2867 on April Fools Day, 1st April 1834 from Felhausen observatory at the Cape of Good Hope with a 45cm. (18-inch f13) speculum reflecting telescope. The appearance of its size and shape would have given John heart palpitations, as he first suspected he discovered a new planet - similar to his father's discovery of Uranus exactly 55 years and 2 weeks earlier. Like the comet observers and supernovae hunters of today, the wait of a possible discovery until the next night must have filled John with agonising anticipation. As a meticulous observer, on the night of the 1st, he began micrometric measurements of the positions of nearby stars to check the planetary nebula's suspected movement.

Why he thought he discovered a planet is a story in itself. Little did John Herschel know how much influence his father's discovery of Uranus would have had on his initial observations of NGC2867, and his eventual astronomical experiences involving the planet Neptune. The possibility of a new outer planet for John Herschel was not a brand-new idea. In the 1820's and 1830's, discovery of this unknown planet was a real and exciting prospect. In the midst of this period, John Herschel left by sailing ship to South Africa in 1833, to conduct his labourious exploration of the southern skies and finish his father's work. Herschel had seriously considered travelling to Australia, but declined the offer made by Sir Thomas Brisbane, because he considered it too far and too long a journey - then several months by ship. His personal and verbal contacts in his younger days at the age of 22 with famous botanist and philanthropist Sir Joseph Banks (1744-1820) may have had some influence on this decision. Banks had become a friend of his father, whom initially contacted Sir William Herschel in November 1781, as President of London's Royal Society, in regards his discovery of Uranus and the presentation of the Society's the Copley Medal. It is likely, that a conversation had occurred between John Herschel and Joseph Banks, would have subconsciously persuaded that Australia was likely far too unsuitable for astronomical observation, and climate-wise, decidedly too unpleasant! Banks had extensive knowledge of coastlines of South America, Australia and South Africa, by his explorations in the 1760's and 1770's on the Endeavour with Captain James Cook.

Far more interesting is in the reasoning why they thought a new planet to exist, and why John Herschel was aware to be on the lookout.

The problem first began in 1782, when Lalande discovered that Uranus was not strictly following its celestial orbit, and was found to deviate significantly from its predicted position. Computations by the mathematicians left them perplexed, and for a time they thought it to be associated with poor observational positions. In the resulting decades, seventeen 'ancient' observations, back to 1670, were added to the data. The true orbit stayed in limbo until the 1820's when better ephemeris predictions were determined. Yet for all the data, Uranus refused to behave itself, and obvious speculations left few alternatives. A general feeling suggested that another trans-uranian planet was causing the perturbations. So from 1820, observers started a new search that was limited to 12th magnitude for the rouge planet. In the 1830's John Herschel had the opportunity to discover new bodies from his location in the southern hemisphere, being the man in the right place at the right time. After all he had a large aperture telescope, and fortuitously, an entire portion of the skies totally invisible from the larger and many moretelescopes throughout Europe and Britain.

History had shown in the decades since the discovery of Uranus, that misfortune had taken its hand on many occasions. In hindsight, both Uranus and Neptune could have been found much earlier.

For example, the brilliant French astronomer Joseph Jerome Le Francais de Lalande (1732-1807) observed and recorded Neptune in May 1795, seeing the planet twice over three nights. He attributing the slightly different positions to be observational error. It is amazing to think that Lalande has discovered Uranus a mere fourteen years before, especially being an active searcher for both the true orbital elements for Uranus and the hunt for new planets! Neptune's eventual discovery turned out to be not a matter of fortune, but a logical and analytical approach to a celestial mechanical problem - specifically the branch known as perturbation theory. On the 26th September 1846, the German astronomer Johann Gottfried Galle (1812-1910) found the new planet. Neptune had appeared near the centre of the field at the predicted position made independently by both the French astronomer Urbain Jean Joseph Leverrier (1811-1877) and English astronomer, John Couch Adams (1819-1892) - a triumph of their mathematical skills.

Sir John Herschel had also played a role in the discovery of Neptune. In June 1846, he was involved with the preparation of an observational search of the presumed trans-Uranian planet. After the planet's discovery, he along with four other prominent continental astronomers of the day; Encke, Gauss, Airy, F.GW.Struve, later proposed on 5th October 1846 the name 'Neptune' to this new planet, which still remains today. Over the next decade, Sir John Herschel remained a central figure in the nationalistic-based dispute between Leverrier and Adams for trophy of the true discoverer of Neptune. They concluded this a decade later, mainly through total boredom with the subject, that we eventually gave both the credit.

In the end, the observations of the planetary nature of NGC 2867 were a false alarm, as the position of the planetary remained fixed. Herschel did checked on it from time to time in the four years at Cape Town, before resuming his life in England, in a slow decline away from observational astronomy. It is appropriated that he discovered it April Fools Day, as the planetary was not truly 'planetary' at all!

John Herschel Observation Records of NGC 2867

1st April 1834;

"The finest planetary nebula I ever remember to have seen for sharpness of termination; 3"arcsec diameter; exactly round; no more haziness about them than would be about a star of the same magnitude tonight (which is a favourable one) Light, a pale white star of 9th mag. Position of companion star=...58.6; star=15th mag. A very remarkable object. Showed to Stone, who distinctly perceived the total difference of appearance between it and a star 9th mag very near it. A second companion star suspected (at about half the distance of the 1st by diagram, and at an estimated position of 330) among multitude of large and small stars."

2nd April 1834;

"Observed with Mr.Maclear, April 2,1834, out of the meridian. Quite round, well defined, and about 3"arcsec or perhaps 4" arcsec diam. Much better seen (between clouds) than last night. The small star is still 1.5 diam. from edge. It has therefore not moved perceptibly, and is therefore not a planet."

26th February 1835;

"Planetary nebula, perfectly sharp; exactly round; not the least hazy or mottled. At 1.5 diam distant from the edge (or taking 12"arcsec for the diameter of neb at 24"arcsec dist from the centre) there is a star at pos = 51.1 ; well examined with Mr Maclear. It bears 320 [power] well, and is quite sharp and uniform with that power."

10th January 1836;

"Planetary nebula, round, equal to 8th mag star; quite uniform in light; quite sharply terminated. Its diameter transits over a wire set to 60 in 4.03 seconds, by a mean of 5 transits. Has a star adjacent pos = 60.7 , dist = 1.5 diam from the edge. About 40 stars in the field, among which two are 9th mag."

10th March 1836;

"Beautifully round and sharp; just like a small planet 3"arcsec or 4"arcsec in diameter at the utmost. Position of the attendant star=...58.5; distance 2.5 diameters from the centre. Shown to Captain Henning."

9th January 1837;

"Diameter 8" arcsec; perfectly uniform in light; sharply terminated, just like a small planet; position of attendants star = 60.7; dist. 1.5 diam; 14th mag. [This is not the PNN.]"

Description of NGC 2867.

In the sixth edition of Rev. Thomas Webb classic 'Celestial Objects for Common Telescopes. Vol 2.'. Espin takes Herschel's original description of NGC 2867 as; "...perfectly sharp and round; 8"sec.arc." Steve Crouch (Southern Sky 1,4 pg.55) quotes; "This object is again fairly small at 12", but its bright bluish disk stands out prominently."

NGC 2867 can be found charted in both Sky Atlas 2000.0 and in Uranometria 2000.0 (Chart 425). It also appears in Norton's Star Atlas 2000.0 - that typically has very few planetaries marked in the charts for amateur observers.

Visual and photographic magnitude of NGC 2867 is 9.7. We can glimpse it in a 7.5cm., though we require an O-III to see it, though a 10cm. clearly sees the PN. The Journal of the Astronomical Society of Victoria 24, 3 (June 1971): "...at limit in 2-inch 200x." is claimed because it would push the optics too much, unless we make them in black skies and perfect seeing.

In size of the outer oval ring along PA 120^O-300^O covers some 14"sec.arc., though a 30cm. will only reveal the smaller 8"sec.arc. inner disk. We could glimpse the outer ring in a 40cm. using with an O-III, though I have not seen it. [N.B. The STScI image (Figure 1.) is overexposed, so we cannot see the 8"sec.arc. central core.] Classified as a Type 4 - ring structure, a smaller amateur 'scope will reveal a featureless circular disk. Greater than 25cm. may see towards the west and southwest, a mottled or darker region of material along PA 220^O to 270^O, and perhaps another dark spot at PA 30^O. All these regions I thought I could see with averted vision.

Further out is a thin extended ring, some 30"-40"sec.arc. from the centre. This ring is unfortunately being invisible to all amateur telescopes except though CCD imaging.

They have undertaken some professional work with NGC 2867, mainly due to the rare occurrence of a Wolf-Rayet planetary nebula nucleus (PNN). This is one of a handful known with the far southern planetaries. (In all only 45 of all planetaries known have these rare very hot PNN stars.) According to calculations by Meatheringham, Wood and Faulkner (1988), the PN is a mere 2 750 years old. In human terms, this is as old as the first recorded Olympic Games held in Greece in 776B.C.!

Based on the measured 9"sec.arc. inner shell of this multiple shell planetary, and using a distance of 2.2kpc., the diameter of the nebulosity subtends about 0.2pc, or 0.6 ltys. If the distance is 1.7kpc., this size decreases to 0.15pc. or 0.45ltys. The mass of the nebulosity is about 0.33 (Solar Masses), though some later observations suggest a lower value of 0.2

NGC 2867 shows evidence of the P Cygni phenomena by observations of the Carbon IV (CIV) at 155.0nm., where removal of three electrons occur in a ratio of 1:7 in the ionisation of the gas. This ratio is the difference between detected electrons verses the total number of nuclei.

The Wolf Rayet Central Star in NGC 2867

Using the Tycho and Hipparchos data, the central PNN star (HD 81119; CSI -58-09200; GSC 8596-0189) is visual magnitude 14.9 (16.6p), having a spectral type of OVI (Smith and Aller (1969)), though Aller (1976) upgraded this into a Wolf-Rayet WC7-8. By 1990 astronomers suggested this to be perhaps closer to WC6, (Some references quote WC3; whose original source I could not find.) an they have often thought existence of a Wolf-Rayet's in planetary nebulae to be a strong indicator of youth. Where in evolution terms, age is based on the time when we reveal a planetary as an exposed white dwarf PNN.

Wolf-Rayets are fascinating stellar objects, and subdivide into two broad types - WN and WC. WN's contain prominent emission lines of Nitrogen, while their fellow WC's have those of Carbon. Unlike most stars, the numerals used in the normal spectral classification are based on temperature, where the lower number shows a slightly high the temperature. In Wolf-Rayets, the values refer to the intensities of the respective Nitrogen or Carbon lines, and to a lesser extent, the Helium (HeI) lines - where the larger the value, the more intense these emission lines appear. In all, the bright-line spectra will show these lines and no others. As Wolf Rayet's spectral profiles can also vary enormously, this confuses the classification system even further. For example, WC6 , WC7, and WC8 stars each display quite dissimilar spectra. Apparently the reason for this is the different ways that the star's energy ionises the surface and its nebulous atmosphere. At one temperature, for example, the C III line may become prominent. For example, at a slightly higher temperature most of the C III (C⁺⁺) gas at 569.6nm. will ionised into a higher state of C IV (C⁺⁺⁺) at 580.5nm. Spectrally, the subdivisions used in the examples follow;

The PNN in NGC 2867 suggests that the spectra may actually change over time, which depends solely on the mass loss from the stellar surface. The nucleus at magnitude 14.7, with the photographic magnitude c.16.6, and therefore, would only be visible using a professional telescope. PNN 1 100 times more luminous than the Sun, and the temperature is 79 000^OK.

It seems that a strong superwind is driving the nebulosity, forcing the gas away from the PNN. Earlier estimates in NGC 2867 showed an escape velocity (EV) c.20kms^-1, however, later values in 1988 tend to favour about twice this value. The shifting or broadening of the prominent spectral lines has measured EV's by Doppler shifting. For NGC 2867, the respective values are 37.1kms^-1 [OIII], 47.1kms^-1 [OII] and 33.3kms^-1 [HeII]. Compared with most planetaries, the inner gas may be in a much high excitation state - so that many ionisation interactions can take place. We reflect this in the estimated moderately high electron density of between 2 200 and 5 000 e^- cm^-3. Observations by Gutiérrez-Morero and Moreno (1988) found and measured radicals ions within the nebulosity, that included S⁺, Ne⁺⁺, Ar⁺⁺, Ar⁺⁺⁺, Cl⁺, C⁺⁺, and C⁺⁺⁺. (Sulphur, Neon, Argon, Chlorine and Carbon) From this they calculated the abundances of the elements including Hydrogen, Helium, Carbon, Oxygen, Nitrogen, Neon, Argo, and Sulphur.
NGC 2867 among all planetaries is also a moderate radio source at 1.3 MHz, which varies in a period of 13 minutes. It is also quite bright in the infrared.

The distance of NGC 2867 in the literature varies considerably. AOST1 suggests a distance of 0.8kpc, which is a gross underestimate. Direct measures of distance today tend to favour about 1.7± 0.5kpc., while the statistical distance is 1.82±0.7kpc.

Surrounding Field of NGC 2867.

Iota ( ) Carinae or Turais (SAO 236808/ HIP 45556/ HD 80404) (09171-5916) is a 2.3 magnitude bluish-white star (Oddly named Richard Allen's 'Star Names: Their Lore and Meaning', as pale yellow) marking the eastern side of the 'False Cross'. Today we know it under the common name of Turais, though others have known it as Scutulum meaning the Little Shield. The derivation of Turais, according to Allen;

"...probably referring to the ornamental aplustre at the stern of the ship in the sub-division of Carina..."

Others, like the Englishman Thomas Hyde, suggested the name as verbum ignotum - unknown meaning.

Drawings by the astrognosist Johann Ehlert Bode in the 15th Century, of the constellation of Argo Navis, is the likely derivation of Scutulum. Here he drew a few of the crews ancestral shields attached, for luck or pride, onto the side of the ship. (This was a common practice in early Anglo-Saxon's and the Vikings, though less common in the ancient world.)

Using the given parallax determined in 1963, the distance is 90pc. or 292ltys., though according to the Hipparcos observations it may be as far as 692±193ltys. As the Luminosity Class is Ib - Turais is certainly one of a few bright luminaries in the Milky Way. Spectra analysed between 1955 and 1962 showed it to be a F0Ib star, though after 1973 this was upgraded to an A8-9Ib star. If this is true, the temperature is about 7 000^OK, with an absolute magnitude of c. -0.2. The proper motion is small, but the radial velocity has been determined as +13.4kms^-1. Iota Carinae is also a suspected variable star known as NSV 4444. Variations are a mere V=0.04 magnitudes, however, a period is yet to be determined. Turais can be found described in Burnham's Celestial Handbook Vol. 2 pg.472, but it seems to me both antiquated and dated.

Asterism (09180-5917) is a line of stars, east of Iota Carinae by 10'min.arc. The brightest star is magnitude 9.3, while the remainder is around 10th and 11th. Some eleven stars in total wind in a north-south direction. We easily see this asterism in a 10cm. telescope, using low magnification.

R111 (09208-5716) is found in a starry field some 55'min.arc. SWW of IC2488 (See last month) or exactly 1.0^O north of NGC 2867. Within a small horseshoe-shaped asterism, R111 lies next to another field 9.8 magnitude star to the east. Discovered by Russell at Sydney Observatory on the 5th March, 1873, with the first measure occurring on the 7th May 1880. His observations record the magnitudes as 11th and 12th, separated by 8.52"sec.arc. at position angle 209.1^O. Later observations have determined the respective magnitudes as 10.0 and 11.0, with only three measures since this time, with the latest being in 1948. This last observation shows an increase separation to 9.2"sec.arc. at position angle 213^O. My estimate in 1992 suggests the separation has increased to about 11"sec.arc. We know few details about this pair, and glancing at the proper motions of the components, it is likely that this is a chance alignment of an optical system.

He2-26 or SA2-41 /WRAY 16-41/ My 47/ PK 278-6.1 (09195-5912) was discovered by K.Henize in 1964. The planetary subtends an angle that was impossible to find without the O III Filter. Perversely, I found it, from a 'cold' start within 40 seconds! It is a mere 18.1'min.arc. due east of Iota Carinae at PA 78^O, and lays west by 3.8'min.arc to an obvious 8.7 magnitude blue star. (SAO 236858/ HD 80901) One problem is the light from Iota Carinae overwhelms the nebulosity, so it is best to place the bright star out of the field, or delete it with an occultation bar. He2-26 is visible in a 25cm., though a 20cm. will show it with care. Photographic magnitude is 11.9, though I estimated the visual magnitude to be c.12 to 12.5.

In the largest of professional telescopes, this object shows bipolarity and extreme filamentary structure. It is another, and is a proposed PN Type I candidate - as first suspect from the images obtained by Westerlund and Henize in 1967. We think such visible structures to be due to shocks and instabilities produced by denser or faster material catching up and accelerating through the material previously ejected in the AGB phase. This also causes large variations in the electron density. As the stars in these objects are often hotter than most, the UV emissions from the PNN together with the varied density distribution, allow such a display of extreme brightness variations within these PN's - and therefore further ionization of the PN shell material. Estimated PNN temperature is 77 000^OK, with the Zanstra temperature of 85 000^OK. This object is similar in many characteristics as seen in the nearby NGC 2899 and NGC 3699. The central star is invisible to all amateur telescopes, and at 16.7, this is understandable. Estimated distance is 2.0 kpc.

He2-22 or SA2-38 / WRAY 16-37/ PB4/ PK 275-4.1 (09152-5453) is a magnitude 12.8 (12.7p) planetary, west of Kappa Velorum by 1.1^O at PA 138^O. Discovered by Peimbert et.al. in 1960, the planetary subtends an angle of 10.2"sec.arc., and lays in a pretty and densely populated starry field. Identification of the field is made with two 8.0 and 9.2 magnitude stars to the NE edge using a medium magnification. The field contains a non-listed triple of respective magnitudes of 8.7, 9.4 and 10.9, in the shape of an equatorial triangle. Using these stars, 6.5'min.arc. away, at a position angle 327^O is the placement of the planetary. This is mirrored by a solitary 10.5 magnitude star on the opposite side and the same distance. He2-22 could not be seen in a 30cm., and found little help using the O-III filter, however at the time I looked the seeing was rather poor. In all, this is surprising, as the magnitude and the size of the object would suggest that the planetary should be easy in a 20cm. (Note: Using a STScI image, I could identify the field stars, but not the PN.)

Visual magnitude of the PNN is 16.12, with a 'B' magnitude of 15.97. (Class 'A' - suggesting a high accuracy.) Temperatures were first rated at 46 000^OK, though later estimates, including the measured Zanstra temperature of 78 000^OK. Distance is 3.36±1.3kpc. is based on eight estimates in the last fifteen years.

The field surrounding He2-22 contains many interesting objects. The first is another planetary that I have not found due to lack of aperture, followed by two pairs and a variable. All can be placed in the one field, if the eyepiece produces an apparent field of 0.5^O.

He2-25/ WRAY 16-40/ PK275-3.1 (09180-5439) lays 28.2' to the NE at position angle 62.5^O. It is best found by the most eastern star of the False Cross - Kappa ( ) Carinae, and moving westwards by 41'min.arc. at PA 300^O. The observed field contains a 6.3 magnitude star, with the planetary being 10.4' due south of this star. Alternatively, the planetary can be found in the same field as He2-22, if this planetary is placed to the SW edge of the field. In the case the He2-25, it will be on the opposite edge of the field. He2-22 is within a trapezium of 11th magnitude stars. The photographic magnitude is stated as 15.4, with a diameter of 5.0"sec.arc. I suspect that a 30cm. could see this if the observing conditions were perfect, however, a 40cm. would likely see the circular nebulosity. The central star is 16.9, and is likely invisible to all amateur telescopes. Little is known about this faint southern planetary.

TX Vela is an irregular variable star that varies between 10.0 and 13.0. Placed a mere 10.4'min.arc. from He2-22 to the west at PA 287^O., I saw the magnitude as 10.5, based on two or three nearby field stars of known magnitude. Little is known about this star, except that it is a yellow G5 supergiant, though I did not see any colour in a 30cm.

Two pairs are found in the southern part of the same field, but both could be clearly separated using a high magnification. The first is HU 1457 (09144-5500), which was discovered by Hussey in 1913. Both these white stars are of near equal magnitude, which is stated as 10.3 and 10.8, respectively. Separated by 1.3"sec.arc. at position angle 260^O. Since the last measure in 1957, the position angle has reduced by 10^O since discovery. The proper motions suggest that the two are likely physically associated. The next pair is FIN 133 (09166-5506), and lies 19'min.arc to the southeast. Using the triple star mentioned in the text with He2-22, continuing in the same direction is best until a solitary 10th magnitude is found. This is the pair. Discovered by Finsen in 1930, this pair is almost identical to HU 1457. Magnitudes are given as 10.3 and 10.4, and are separated by 1.7"sec.arc. at PA 273^O. Again the proper motions suggest that the stars are associated. In all, both stars can be separated in a 15cm., with care, and easily in a 20cm.

IC 2501/ He2-33/ WRAY 16-54/ SA2-47/ PK281-.51 (09388-6006) was discovered by Fleming in 1904. It lays 3^O east of Iota Carinae, or alternatively, 1.2^O due north of the 4.7 magnitude m Carinae (SAO250653). The planetary appears in both Sky Atlas 2000.0 (Map 25) and Uranometria 2000 (Map 426). This planetary proved difficult to find, even with a decent finder chart, and appears starlike even though the photographic magnitude is 10.4 and the visual magnitude is 10.6. The reason is due to its small size of a mere 2"sec.arc. In both AOST1 and AOST2, the descriptions are exactly the same - except that each state the respective diameters as 2"sec.arc. and 5"sec.arc. I cannot ascertain the diameter of 5"sec.arc., but I assume this from the photographic image. We can just see IC 2501 in a 15cm., and easily in anything larger than 20cm. Sprinkled with moderately faint stars, however, this is definitely not one of the star spangled fields normally seen in the central Milky Way! A bright 6.9 field star (SAO 237160) lies within the field of a moderately powered eyepiece, with the PN being some 15'min.arc. to the southeast. The O-III was not as effective on the identification of the small disk, though when found, flicking the filter across the field, it does reveal a slight brightening. Observers should try to find this object on nights of good seeing, preferably with a telescope that performs well using high magnification. I saw no colour with this object, and though it was more like the 'Ghost of Neptune' - perhaps an apt common name for IC2501!

The central PNN (HD83832/ CD-59 2483) has a visual magnitude of 14.48, which is invisible to all but the larger amateur telescopes. In the literature, it is obvious that we know little about this star. We have obtained a few images of this object, with the most recent being by Schwartz and Melnick (1997) using the ESO-NTT facility.

IC2501 is a strong but small IR Source among all known planetaries, as first obtained by IRAS in 1982 at wavelengths of 3.3 and 3.4 microns. Strong spectral lines observed in 1982 suggest Silicon Carbide (SiC) grains exist in the 8 and 13-micron range. We often observe these in carbon star atmospheres, and this acts as the evidence of the connection with the red giant phase in a star's life cycle and PN's. Concurrent UV observations have also shown this SiC feature is prominent. The ratio of Carbon to Oxygen is about 10:9. (C/O =0.9). Radial velocity is towards us at +32.7±1.0kms^-1, while the latest distance estimates suggest that the PN is 1.8± 0.3kpc. from the Sun. It is interesting to note the Hartung (AOST1) gives a distance of 1.65kpc. For 1968, this is very close to the mark!

In all, IC 2501 is a good challenge for amateurs to attempt to find, and an observer with less than a 15cm. will need all their personal observational skills to find it.

Surrounding Field of IC2501.

HJ4240 (09433-6002) is an 8th and 10th magnitude pair 34'min.arc. east of IC2501. Although discovered by Sir John Herschel, Lawrence Hargrave made the first measures at Sydney Observatory on the 12th May 1882. Separated by 12.4"sec.arc. at PA 57^O, little has changed in the positions in the last 116 years. I saw the colours as bluish and white, which is easily visible in a 7.5cm. According to the WDS96, the magnitudes are 7.5 and 10.0, with a primary's spectra being B5V.

GW Car (09364-5959) is an EB/KE* eclipsing binary that lays in the same field as IC2501, some 1.9'min.arc. along position angle 287^O. Visual magnitude variations change between 9.55 and 10.1 in a period of 1d 03h 05.6m (1.128911 days.), based on the starting date on the 23rd October 1941(JD 2430291.0395). The blue B1 III star show nebulose characteristic in the spectra, suggesting that the stars are, or have been, in the process of mass transfer.

* KE classification is a contact binary whose components have early spectral types in the range of O- types and A4 spectral types.

Postscript:

Since writing this part of Neat Southern Planetaries, I have come across the HST image of NGC2867 (and about eighteen other images that includes some popular planetaries discussed in this series.) labelled 'SSU Final Blaze of Glory', at the STScI website. http://oposite.stsci.edu/pubinfo/pr/97/pn/

Although the image was obtained for Howard Bond (STScI) in 30 June 1985, it has only been made available for pubic last month. As yet no press release has been given for NGC2867. Taken with the Wide Field Planetary Camera (WFPC2), the field size is small, and covers some 400x388 pixels. Some caution should be used with the picture, as it is a combination of an infrared image peaking at 745nm, and a visual filter peaking at 540.7nm. Exposures were, respectively, 500 second and 140 seconds. The image shows north at the top, with the field east facing the right-hand side of the image. For ease of seeing the image in UNIVERSE, I have converted it to grayscale as a negative. To me the nebulae now looks more like a sunspot than a planetary! The three stars in this small field are likely about 18th magnitude.

Appearance of the ionized gas reflects the turbulent mixing, that is often thought to be cause by intense magnetic field of the new white dwarf, and the direction of the mass loss during the previous red giant's AGB phase.

Some features are familiar with the telescopic view, and explains the mottling effects seen inside this 12"sec.arc. disk. (Note: Visually we see c.8"sec.arc.) The suspected 'dark region' at position angle 220 [degree] -270 [degree], corresponds to the small bay or indent in the near circular disk at more like 240 [degree] PA.

Along PA c.160 [degree] is a discrete bulge that was not visually seen in a telescope. Note the central PNN star is clearly visible. Those with larger apertures >40cm. they may see the planetary appearing more oval in shape, and any of these structural features.