sponsored by psychohistorian.org
RA: 15h 10m 40.74s
Dec: −64° 40′ 28.5″
Con: Triangulum Australe
Ch: MSA:998, U2:453, SA:25
Type: planetary nebula
Mag: B=?, V=?
Select a sketch and click the button to view
Select a photo and click the button to view
Discovered by Sir John Herschel at the Cape of Good Hope with an 18-inch f/13 speculum telescope. He recorded it as "pB, R, vgvlbM, 60 arcseconds." On a second occassion he called it "pB, R, vgvlbM, 70 arcseconds."
From: "Neat Southern Planetaries - IV."
This region of the sky is an interesting, yet often neglected area by amateur observers. It contains two enigmatic planetaries one of which has a most bizarre history. The area of the first contain various pretty pairs, a dark nebula and several marvellous asterisms. The second area is near an interesting globular and a number of pairs.
NGC 5844 (PK317 5.1/ SA2 115/ WRAY 16 168/ He2 119) (15107 6440) TrA is part of a small arc of stars in the eastern portion of Triangulum Australe. According to most of the modern computer software that uses the Hubble Guide Star Catalogue, there is on right on top of the planetary a bright 7.6 magnitude bluish star (GSC9029:2732) that is not there. (See Endnotes.)
NGC 5844 at position 15h10'42.0" 64O41'00 is listed as nonexistent, while the planetary SA2 115 is positioned at 15h10'39.9" 64O40'19". The difference is a mere 52.8"sec.arc. so likely that the two objects are really the same. (I will assume it is!) The original description by Dryer in the NGC was PB,PL,R,VGVLBM - Pretty Bright, Pretty Large, Round, Very Gradual and Very Little Brighter in Middle. A rather odd designation for this object, as it does not match its telescopic appearance. It has also been deleted from the revised NGC catalogue and no reason is given for this deletion. However, this difference has meant that most Star Atlases and Catalogues including Sky Atlas 2000.0 and Sky Catalogue 2000.0, Uranometria 2000.0 (map 452.) etc. have not listed this fairly bright and interesting planetary. Recently, a Bowen Mountain all were surprised at the brightness of this object, especially as it lies close to the rear end of Triangulum Australe and Beta Centauri. Using the 0.45 metre telescope at Bowen on the 23rd August 1997; Mick McCullagh and Don Whiteman (for their first time peek) took sometime to find this object among the brilliantly starry field of Triangulum Australe. When it was found, it was obvious. (Even some local visitors looked at this object, but as first timers I suppose they didn't understand the implications of what they were seeing. However, I did give an explanation the general nature of planetaries and their evolutions.)
To find this object, it is best to use the star Triangulum Australis in the middle of the base of the 'southern triangle' and the star Circini. Draw an imaginary line between the two stars. Divide this line by quarters, and move towards TrA from Cir by a whole quarter. This centres directly on the planetary where two 8th magnitude stars appear within the same field.
The visual magnitude is stated as 12.1 while the photographic magnitude of the planetary is 13.2. In size, NGC 5844 subtends an angle of 53"sec.arc. AOST2 states that this object is "..70"x50"sec.arc.", that is partly incorrect as even the photographic image never exceeds 55"sec.arc.
As an ovoid shaped object it is just visible in a 15cm., best found using an O III filter with medium power. In AOST2, David Frew states that it can be easily found by blinking across the field an O III filter. This is true for a 10cm. or 15cm. telescope, but any larger aperture can immediately detect its nebulosity. Using an O III filter, the brightness is fairly even across the entire disk. I could also see a slight indentation in the northern edge of the planetary. Using a 30cm., the appearance of this indent becomes more pronounced, revealing an uneven edge, and this turns into a "bay" in telescopes exceeding 40cm. A 40cm or larger should also start to see some structure in the planetary perhaps more obvious using an O III or using a Hydrogen Beta filter. Observers at Bowen, including Les Sara, thought that the appearance seemed mottled and even more so with the O III. Some faint bipolar features were also noted, with some difficulty, by each of them.
The PNN central star is invisible in all amateur telescopes and with a stated magnitude of 16.6 this is understandable. Little in the literature is written about this object until the beginning of the 1990's. Any observational data available remains scant. Distance has been recently determined (c.1996) at 2 900 kiloparsecs.
The corresponding lack of data is a reflection of the poor quality of information on the object's catalogued position, perhaps more so with the rejection in the RNGC. Again, the northerners have actually 'butchered' this most wonderful object. Yet, if it were in the northern skies we never hear the end of it! I recommend that members of the ASNSW have a look at this object. If you do so, please write a letter to the Editor (or to me.) If we can get enough information, we could punish those northerners by telling them in no uncertain terms what they are missing!
The Surrounding Field of NGC 5844. (See Field Chart and the Endnote.)
B832 (1510.9 6439) is a pair 4.0'min.arc. east of NGC 5844. Both stars are magnitude 9.4 and 11.4, respectfully, appear as yellow and orange. Since the first measure in 1927, little has changed with these stars that are separated by some 4.8"sec.arc. at position angle 79O. West of B832 (15085 6438) by 17.0'min.arc. W and 3.0' N of NGC 5844, is a second pair B831. The magnitudes are 8.7 and 10.9 respectfully, separated by 2.6"sec.arc. towards PA 108O. Little has also changed with this pair in the last seventy years since its discovery. I see both stars as yellowish white.
Asterism. Located 13'min.arc. NEE (PA ~55O), and centred on position RA 15h 12m 23s Dec. 64O 32' 29" is a lovely asterism of eight stars and finding it is easy. This object has no common name, and is not listed as a multiple star. The two brightest and closest stars (GSC9029:374 and GSC9029:167) are magnitudes 7.4 and 7.8. All the other stars are between magnitudes 9.8 and 13.8 in an area of about 4.0'min.arc. It would take a 20cm. in dark skies to see them all, that is best viewed using medium magnifications. (c.200X.)
Asterism. Centred on 14h51.0' 66O 12' is another brighter asterism that my friend's 14 years old daughter Alexandra Popovic coins 'The Golden Horseshoe.' It lies between Alpha ( ) Circini and Gamma ( ) Triangulum Australis, and some two thirds the bisected distance in a straight line between these stars. To the naked eye the brightest star in the asterism is the 6.2 magnitude bluish Zeta ( ) Circini (SAO252951). The Golden Horseshoe has a diameter c.0.8O and contains some 25 stars three of 6th magnitude, six are 7th, eleven of 8th and five of 9th. It also contains a number of double stars.
In the finder, this asterism is obvious, though the larger telescopes may have serious trouble in getting the object within the telescopic field. A small telescope, say 7.5cm. or 10cm. using low power will have no trouble placing it into one field.
Asterism. Another 'mini asterism' lies in the northern part of the 'horseshoe', which I call the 'Golden Snake'. This is an 'S' shaped line of stars that extends NNE from the 7.6 magnitude star SAO252951 (GSC9019:467) by some 12'min.arc. in length towards Alpha Circini. Twisted like a snake, the line of twelve 11th and 12th magnitude stars end in a 'forked tongue'. A 7.5cm. should see these easily in dark skies, a 10cm. if you are in a sky lit suburb.
Between the 'Golden Horseshoe' and Circini is a dark nebula. Typically dark nebulae are boring. However, this one is interesting because of a major drop in the number of stars both east and south of Circini, and this is visually obvious some 1 degree East of Circini. Astrophotographers using a 50mm. or 55mm. lens on a SLR will readily see the object. (Note: If you have already have a 55mm. photo that has Alpha Centauri and the Cross in it; you probably can see this in the bottom left hand corner!)
. . . . .
Footnote 1: Problems Identifying This Planetary.
The Guide Star Catalogue, designed to be used with the Hubble Space Telescope, is notorious for having errors with non-existent stars (c.20%) and misidentifications of known NGC and IC objects. Most of these have been 'sifted out' by observers like Brian Skiff, amateurs and professional astronomers by noting differences when observing objects. Fortunately, most happen to be faint objects.
This 7.6 magnitude bluish star (GSC9029:2732) stated in the catalogue proved to be a difficult object to explain.
In the GSC positions, according to the CDS listing of the catalogued position is 15h10m41.01 64O40'23.0". The source of the data is a taken with the UK Schmidt on March 1976 (Epoch 1976.256 ) using a IIIJ emulsion and a GC395 filter producing a derived magnitude was 7.61� 0.45. Visually, no star appears at this position nor in a number of other photographs of this region. The STSi image also shows no star. No star in this position is stated in the SAO or any of the preceding catalogues. Also the positional data of the centre of the planetary He2-119 and this 7.61 magnitude star is a mere 1.1"sec.arc North and 5"sec.arc. East, well within the NGC 5844 boundary.
No asteroids were near this position during 1976 and no known variable stars. It is not in the New Suspect Variable (NSV) listing and no known nova is expressed for this object. It is obvious that a problem exists with this star.
Twenty three references were found during an Internet search with SIMBAD. Strangely, there is no reference to the PNN, nor of this star. The nearest star is GSC9029 1442 at magnitude 12.51�0.22 is stated at this position; 9"sec.arc.W, 43"sec.arc S; but and I could not visually identify this star either!
At first, it was compelling to think that this star is a novae or variable associated with the planetary.
After some checking (and extensive personal searching) a final reply ended the debate. This was received by via E-mail on Saturday 30 Aug 1997 from Gareth V. Williams the Associate Director of the IAU Minor Planet Center at Harvard University, Cambridge, MA;
"The "star" GSC 9029 2732 is actually an artifact of the plate measuring process and is simply a measurement of the "center" of the planetary nebula NGC 5844. Normally measurements of non stellar objects would be so flagged in GSC, but this object appears to have escaped that classification. I note that NGC 5844 also appears in the USNO A1.0 catalogue, a list that is supposed to contain only stellar objects."
This apparent chaos seem likely because of the presumed non-existence of NGC 5844. If the catalogues are wrong, then observers will tend not to place it in their observing programmes. Although this proved not to be an 'historical nova', its final value at least will correct updates of catalogue listings. It proves that for all the technical marvels of modern astronomy mistakes still occur.
Interestingly, there remains one puzzling question that still cannot be explained; How could the magnitude of this "star" be measured at 7.6 if the planetary nebula has a visual magnitude is 12.1 and photographic magnitude of 13.2?
Footnote 2: Something is Seriously Wrong With Space.
(Title taken from Chapter 31 of Arthur C.Clark's: The Lost Worlds of 2001)
This field is strange to about 5deg surrounding NGC 5844. Firstly, the SAO catalogue has some stars placed in this region, while others, and sometimes brighter stars are not listed. For example, surrounding the region of NGC 5844 some other 9.5 magnitude stars are listed. Using my own versions of Atlas Australis and Uranometria 2000.0, I had some trouble identifying the actual field. Between the declinations between 64O and 65O, the SAO is both inaccurate and poorly surveyed.
The reason for this might be the original data in the production of catalogues in this region where the problem seems to have started with the beginning of the Astrographic Catalogue in the 1880's. Declinations to be surveyed were delegated to various sites. Those north of declination 64O were delegated to the Cape Observatory in South Africa. South of 64O this was allocated to both Sydney Observatory and Melbourne Observatory. The 'Cape Catalogue' was used to update the positions of stars to 64O . .Later of the 50 000 stars, some 15% of stars were rejected because no data on their proper motions were given. In essence, stellar positions in the declination range of 52O to 64O have a few stars simply not listed. When the Astrographic Catalogue was eventually completed in 1936 these rejected stars did not make there way in amateur atlases from the 1950 onwards. (Note: Some additional data used in the SAO is also taken from Vol.20 of the Ann. Cape. Obs. Catalogue by Jackson and Stoy. (1950.0))
South of 64O, the details become very confusing. It seems that some procedural policies in producing the southern parts of the catalogue were different than at the Cape Observatory. Firstly, the magnitude limit is not as extensive from 64O to the pole. Secondly, it seems that the first stars, and therefore the oldest positions, are in the region of declinations 64O to 66O. The data for these stars in the declination range were original made using the 'Third Melbourne General Catalogue, Reduced without Proper Motion to the Equinox 1900.0', eventually published by Ellery and Baracchi in 1917. Again, many stars without known proper motions were not eventually listed in the SAO.
What this means is that many earlier atlases before this time are relatively poor when identifying stars. If you own a computer program, such as RedShift 2.0 - notice the sudden drop off in stars in the declination range of 64O to 66O. (Make sure it is SAO orientated data and not based on the more realistic(?) GSC Guide Star Catalogue.)
Amateurs identifying fields in this region should be cautious especially object below c.7th magnitude. This includes the constellations of Pavo, Triangulum Australe, Circinus, southern Crux, northern Musca, southern Carina and northern Volans. Soon, the general introduction of the Hipparchos and Tycho catalogues to atlases will not have this problem with identification. This will reduce the uncertainties in this area to magnitude c. 11.5, but at the moment, no deeper.
In regards NGC 5844, I am unsure if it has played a part to the misidentification of this object. To me, NGC 5844 is very likely SA2 115/ He2-119/PK317 5.1.
The RNGC (Sulentic and Tifft 1973) notes that this is a unverified southern object.
Table IV: As in NGC, 3 vF neb. only.
= PK317- 5 1 = He2-119
15cm - vis w/o filts @ 80x as sm losfcbr puff. [OIII] & UHC are equally
effective. 140x: 40" diam, circ, roughly uniformly br. vf pair off E
side; brtr pair ENE; m9 * N is also un= pair. BS, 24Feb1990, LCO.
12-inch f/10 SCT (95x 218x 346x)
The planetary nebula is situated about 13� towards the south-west of a bright magnitude 7 double star with a fainter double star situated just outside the north-eastern edge of the planetary nebula. With very high magnification the object can be seen in a slightly north-west to south-east direction. Certain data basis shows this object to be a double planetary nebula with the other PK 317.1-05.7. With care I spot a faint marking towards the middle area on the visible surface.
RA: 15h10m42s - DEC: -64o40' - Magnitude: 12 - Size: 1'
Tel: 12" S/C � 218x - 346x - Date: 14 June 2009 � Vis: 5.6
The soft elongated glow made itself quite evident in this busy star field. The nebula is elongated in a north-west to south-east direction. High power and a nebular filter show the south-east lob of the nebula slightly more hazy but brighter, whereas the edge of the north western part more define but fainter. Afterwards I realize the nebula to be two planetary nebulas consist of NGC 5844 (south-east) and PK 317.1-05.7 (north-west).
16-inch f/10 SCT (127x, 290x, 462x)
Slightly elongated NW-SE and what looks to me more open to the top north. Not even, in structure but knotty patches been seen. What is going on here, another planetary involved or one planetary double lobbed. Towards NE 13' is a 9Magnitude star that seems double
The Messier objects
The Bennett objects
The Caldwell list
DOCdb is still in beta-release.
Known issues, feature requests, and updates on bug fixes, are here:
Found a bug? Have a comment or suggestion to improve DOCdb? Please let us know!
DOCdb is a free online resource that exists to promote deep sky observing.
You could help by sharing your observations, writing an article, digitizing and proof-reading historical material, and more.
Everything on DOCdb.net is © 2004-2010 by Auke Slotegraaf, unless stated otherwise or if you can prove you have divine permission to use it. Before using material published here, please consult the Creative Commons Attribution-Non-Commercial-Share Alike 2.5 License. Some material on DOCdb is copyright the individual authors. If in doubt, don't reproduce. And that goes for having children, too. Please note that the recommended browser for DOCdb is Firefox 3.x. You may also get good results with K-Meleon. Good luck if you're using IE. A successful experience with other browsers, including Opera and Safari, may vary.