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Type: supernova remnant, C
Mag: B=?, V=?
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New nebulae shown on Franklin-Adams Chart plates. MNRAS, 86(8), 636-638.
Southern clusters and galaxies. Harvard Obs. Bull., No.914, 6-8.
6. Bright String Nebula in Vela. - An exceptional streak or string of emission nebulosity in Vela has been photographed on long-exposure plates of various series made at the Boyden Station. The chief peculiarity of the nebula is its length and narrowness. On the Bruce plates (1arcmin=1mm) it can be traced for about four degrees, and throughout most of its winding course it is between 1' and 2' in width. On the plates (2.8'=1mm) made with the Metcalf triplet, the nebula can be followed continuously through an irregular wavy arc for about 4.5°, from a point 15' north of e Verolum (8h 34.2m, -42°38', sp. A5) southwestward to a point half a degree south of H.D. 72127 (8h 26.0m, -44°23', sp.B5).
There are a few naked-eye stars in the vicinity of this emission nebula with spectral class B3 and later, but no conspicuous blue star has been found near the center of the arc, which has perhaps a radius of two or three degrees. Halfway along the nebula there are some faint branches on the concave side. The whole nebulosity is faint, and it would be reasonable to expect that further extensions of the faint emission might be detected on a photograph taken with a suitable Schmidt-type instrument. The near-by Milky Way star clouds are strongly marked with absorption nebulosity.
The coordinates (1900) for the middle of the string-nebula arc may be taken as
alpha = 8h27m, delta -43°15', lambda=230°, beta=+3°
"An optical atlas of galactic supernova remnants" [1973ApJS...26...19V]
Photo index by Jim Lucyk: Sky & Tel. 5/88 p480, Sky & Tel. 4/87 p217, Sky & Tel. 7/79 p35
I observed the Vela Supernova Remnant one year at the Winter Star Party. Alex Langousis brought me over to see it through his 15" Newtonian equipped with an OIII filter. It was quite beautiful.
Since I fly to the Winter Star Party, I bring a relatively small scope - an AP Traveler. The Vela SNR is so large, I thought it might make a good target. I was surprised how nice it looked. I wandered off to get Alex. His commment was gratifying, "It makes me wonder why I dragged a 15" down here."
My notes on the object are more sketchy and not nearly as poetic as yours, but here they are:
2-6-97 10:45 PM EST 4.1" f/5.8 Apo 35mm Panoptic + OIII filter
Seeing: fair Transparency: good
An astounding complex of nebulosity stretching across several degrees of sky. The brightest sections lie north and west of e Velorum. A large detached T of nebulosity lies east of the main, sprawling complex.
2-7-97 10:20 PM EST 4.1" f/6 Apo 35mm Panoptic + OIII filter Seeing:
good Transparency: good
Even more obvious than last night. Extremely complex. Gum 17 is also visible with a dark nebula encroaching into the east side.
Obviously these words fail to convey the image. It deserves a sketch if I ever get back to WSP. Regardless, the Vela SNR is a good target even for a small, wide-field scope.
Clear skies, Sue
Congrats to your observation of Gum 17 and the dark nebula (Sandqvist- Lindroos 4)! This is the first time I see an observation of these objects other than mine. SL4 has the size 60'x10', opacity 5 (very dark) and irregular. It is missing from MOL. Sky Catalogue calls Gum 17 incorrectly as RCW 3 (should be RCW 33) and it is missing from MegaStar. Size 100'x65'. I used a 17.5" reflector @95x (without nebula filters) from Western Australia. The dark nebula made a bend to the N.
The interesting "Pencil-nebula", NGC2736, was about 20'x1' as seen with a C-8. The nebula is classified as a galaxy in Saguaro Astronomy Club database! Strangely, it is missing from Burnhams Celestial Handbook, Sky Catalogue and MegaStar, for example.
Have any of you seen Gum 23 (RCW38) or Gum 25 (RCW 40)? I saw Gum23 as "pretty bright but rather small" with the same equipment as above. Gum25 was "pretty faint but large". The stars inside it formed an "L"-shape.
12,000 years ago a supernova event marked the catastrophic end in the life of a massive star in the constellation Vela, a large constellation representing a sail on the giant ship Argo in the southern sky. The self-destruction of the star released a huge amount of energy as radiation, but a substantial fraction of the force of the explosion blasted the outer part of the supernova into an expanding shell of matter that traveled through the almost empty space between the stars.
As the rapidly moving blast wave encountered the relatively stationary interstellar medium it created a very narrow, luminous shock front that appears as a huge faint nebula.
The Vela Supernova Remnant is one significant part of the Gum Nebula (Gum 12), a complex shell of faint nebulous filaments. It is the largest object in the sky, apart from the Milky Way, and measures 36 degrees across Vela and its neighboring constellations. It is a half shell of filaments similar to the Veil Nebula in Cygnus, and was discovered by Australian Astronomer Colin S. Gum in 1952.
A haunting David Malin photograph of a portion of the Vela supernova is one of my favorite astrophotographs. Cut out of an AAT Astronomy Calendar, it is hung on the wall right above where I store my 12.5 and 17.5 inch LITEBOX reflector travel telescopes. I added the Vela Supernova Remnant to my Ayers Rock observing projects soon after I sent in my deposit for the once in a lifetime observing trip I recently concluded. This April trip was organized by Tom Clark and 32 of us Amateur Astronomer magazine subscribers had five spectactular observing nights at -25 latitude on a aboriginal land observing site within site of Ayers Rock..
My first challenge was to identify the constellation of Vela, sort of a sideways Auriga shaped constellation above the Orion arm of the Milky Way. Then I had to identify the triangle of three stars - zeta Puppis, lambda Velorum and gamma Velorum - a Wolf-Rayet star and a double star as well.. Most of the significant areas of the Gum Nebula are contained within this triangle, nestled between these amazing stars in this awesome section of the sky. This area is too large to fit on one Uranometria page, so it took me a while to see the triangle, though all three stars are very bright. Volume 7 of the Webb Societies Deep Sky Observers handbook series - the Southern Sky volume was a great help, and my great San Francisco observing friends Toney Burkhart and Bill Cherrington helped me immensly by designing some projects of their favorite objects, printing out Megastar charts for my observing projects each night, as I would not be brining a computer. One 12.5 inch travelscope, a camera and tripod, arsenal of eyepieces, and some 9 X 63 Celestron binos for southern sky scans added up to overlimit luggafe as it was.
The good ship Argo (and all its multi- constellation segments) contains more naked eye bright stars than any other constellation in the sky - 676 stars to be exact. That's alot of stars to wade through. Once I found the triangle I placed my 22 Panoptic in the focuser of my 12.5 inch reflector and took a little 84X spin around Vela and Puppis. I knew this object would be difficult, much like looking for the Veil Nebula in a light polluted front yard without a filter. I saw nothing at first!
I borrowed an OIII filter and tried again. I thought perhaps I had detected a very subtle change in the view through the eyepiece, but it was so subtle that I called others over for a look. No one else could see anything for sure, either! I offered LITEBOX telescope designer, owner and user Barry Peckham the opportunity to trade telescopes for a little while. The extra aperture offered in the 15 inch version of his LITEBOX reflector, which was his travelscope on this adventure, as compared to my 12.5 incher, might just make the difference between seeing and believing.
Switching to his 27 Panoptic with the OIII filter in the F5.5 15 incher did indeed make a difference! Soon long ribbons of nebulosity snaked through the eyepiece. Just like the Veil Nebula, the circular shaped shell of star stuff twisted and curled in delicious tendrils of filamentary magic. It was very dim, but the long pencil shaped ribbons and streamers could be followed easily by pulling down on the big dob. Chunky and curvy sections abounded. Soon the snaky line was not only in the eyepiece, but behind the LITEBOX as well. Everyone had to take a look at stellar history!
That long pencil shaped remnant turned out to be the Pencil Nebula. This is an outlying wisp of the Vela supernova remnant, almost the only sign of the eastern part of this vast bubble of expanding shock wave. Many fine, tangled filaments are seen in the western part of the nebula, but in the east, most of it is hidden in dust. This is one of the brighter eastern fragments, and its unusual linear appearance in the telescope was remarked on by Sir John Herschel who discovered this nebula in the 1840s. This spindly shape is the source of its popular name.
I cataloged many individual objects within this golden triangle in my sketch book and note book. There were dark nebulous patches, double and triple stars, fascinating planetary nebulae of the most beautiful hues of green and blue and clusters, and clouds galore. And my complete 110 object catalog (a la Mr. Messier) of southern sky "must see" objects may be of interest to some of you anticipating a trip down under.
But my most vivid memory of this particular night - the third of five in the Australian outback was to imagine how this area looked to the Aborigines 12,000 years ago when a brilliant light shown in their sky for a month or more. A star burst the size of the moon! Star burst carvings in New South Wales may be the observers log from these ancient and noble accidental astronomers.
For those of you who may be interested in reading the other adventures through a 12.5 travelscope in the Australian Outback, please go to my club reports which are located on the Hawaiian Astronomy Club website: http://www.hawastsoc.org/. Click on Barry Peckham's observing report, which includes some images I took of our adventures. Then my five writeups are linked - this Vela Supernova Remnant story is excerpted here. I hope you enjoy this adventure of a Northern California girl experiencing the majesty of the southern sky.
Have telescope, will travel
I stand corrected by Tom: the stuff you see is Vela SNR, _not_ Gum Nebula pieces. Brian
Last year at about this time I immersed myself into a project of learning the true identities of the Gum Nebula and Vela Supernova Remnant. The search through the literature was launched by a sentence in the ESO book "Exploring the Southern Sky" that reads: "The Vela supernova remnant appears against the Gum Nebula in the sky." Most other books incorrectly call the Vela SNR the Gum Nebula. The two are quite different.
The Vela SNR is much like the Veil Nebula in Cygnus: a large supernova remnant highly excited in the [OIII] line. It is 6 degrees in diameter, which seems pretty large until you come across the numbers for the Gum Nebula. It is a large H-alpha emitter that is now known to be over 36 degrees across! For those with access to good reference libraries, the discovery paper by Colin Gum from 1952 is Observatory 72,151. Subsequently, great H-alpha photos that show its true extent were published in 1982 in A&A 121,19. This paper is available electronically from the ADS.
I know these are fighting words for hard-core deep-sky types, but I doubt that any portion of the real Gum Nebula is a visual object. On the other hand, the Vela SNR is a stunning network of filaments. My first view of it was from Chile with a 13-inch. It is not as bright as the Veil, but it just goes and goes! Describing it was very difficult, as Jane Houston mentioned, so I'm stuck with four schematic sketches of 1-degree fields as my body of notes on this object. The Vela SNR skims the horizon in southern Arizona, where it is faintly visible through the desert crud. Unfortunately it does so in Winter, when this desert rat does not want to observe from the cold high country.
Attached below is a message I sent to Roger Sinnott just before publication of the Millenium Star Atlas. I was able to convince him not to perpetuate the misidentification, and it is plotted in the atlas with the correct label "Vela SNR."
I located Colin Gum's paper about his nebula discovery. He certainly was not describing the Vela SNR, which was known about at the time of the paper. In "The Observatory" 72,151 (1952), he writes:
"An area of H-alpha emission about 20 degrees in diameter at galactic coordinates l=226 deg. b=-8 deg. has been found from observations made with the 130 foot nebula spectrograph at the Commonwealth Observatory. ...Direct photographs were taken with 103a-E film with Wratten filter No. 29."
He then points to a figure that plots the giant region centered at roughly (1900.0) 7h 55m, -44d. To confuse matters, the galactic longitudes seem to be incorrect. I get l=255 deg., b=-6 deg. for his position. Has the galactic coordinate grid been changed since the 1950's? This 30 degrees is too much for precession.
Gum refers to the an object that is the Vela SNR in this paper: "...Shapley(4) found a "string" nebula 4.5d long, part of which appears on Fig. 1 at 8h 30m, -42d 35'." That position describes the bright northern end of the Vela SNR well. Ref. (4) is "Harvard Bulletin No. 914, p. 8 (1940). I don't have access to that paper. So although it wasn't called the Vela SNR, it was known about as early as 1940, and is recognized in Gum's paper. He makes no speculations as to whether it's part of his new nebula.
I gathered up some much more recent work including a paper from 1997 that is as confused as ever. Enter the IRAS Vela Shell and the Vela Molecular Ridge, which also appear to be unique objects lying in the same general direction! The Vela SNR is a strong [OIII] emitter, while the Gum Nebula shows almost no [OIII] emission; instead it's primarily H-alpha. By the way, the Vela SNR is spectacular through an [OIII] filter. I doubt the deep red Gum Nebula would be visible in any instrument.
On another day I would like to find out when the Gum Nebula was first called the Gum Nebula, and when the nature of the Vela SNR became clear. It's apparent from the 1997 paper that there are still many mysteries with the Gum Nebula.
Is this subject of interest for S&T readers?
Arizona Sky Pages
I went through a lot of material trying to sort out what is what in that region. There was an IAU symposium on the area that was quite helpful. Most of the stuff actually thought to be SNR was more filamenary than the rest.
Clear skies, Sue
The various observations of the nebular bits in Vela are interesting. I'll let Tom Polakis comment on the attribution of the various parts to the Gum nebula and the Vela SNR, which are apparently unrelated but overlapping on the sky. I think what most of us call parts of the Vela SNR are actually pieces of the Gum Nebula. Perhaps for visual observers, the collection could be called the "Vela nebular region" or some such. I might mention here that nearly all my 1300 or so observations done from Chile with my 15cm refractor are posted to the Lowell ftp area starting at:
...where things are arranged by constellation. The MC observations are binned separately under NMa (Nubecula Major) and NMi (Nubecula Minor). There's also a 'readme' file at the top of the directory. Because of the consistently excellent seeing in Chile (Las Campanas Observatory), I regularly used an eyepiece/Barlow combination yielding 195x in the 15cm refractor---rather higher magnification than is usually recommended for deep-sky work. The extra few tenths of a magnitude threhsold it provided (compared to my usual 140x "working power") was pretty much indispensable in the Magellanic Clouds.
You are right. There is an article in Sky&Telescope February 1975 (I'm sorry, I don't know the pagenumbers) describing the "Vela nebular region". According to the article is the distance to the SNR about 460 pc while the distance to Gum 17 is 900 pc. Thus, it seems definitely that Gum 17 belongs to the more distant Gum nebula. Gum 17 also lacks the typical filamentary structure as in the Vela SNR.
Another delayed response, this time on the nebulae in Vela and Puppis. You might be interested in cool and colorful wide-field photographs of this region at the website of the Mount Stromlo H_alpha Survey:
(go to 16-inch instrument images).
Leos Ondra, Skretova 6, 621 00 Brno, Czech Republic
The Messier objects
The Bennett objects
The Caldwell list
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