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Thread: Object of the Week March 16, 2014 - Eight Burst Nebula

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    Member deepskytraveler's Avatar
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    Object of the Week March 16, 2014 - Eight Burst Nebula

    NGC 3132, He 2-40, PN G272.1+12.3, PK 272+12.1, Eight Burst, Southern Ring

    Planetary Nebula

    RA: 10h 07m 1.89
    Dec: −40° 26′ 11″

    Size: 1.4’

    Mag: 9.7v, 8.2p


    The Eight Burst Nebula, NGC 3132, is a bright and extensively studied planetary nebula in the constellation Vela. Also known as the Southern Ring Nebula, in Hubble photos it bares a remarkable resemblance to M57, the Ring Nebula. The biggest challenge for many to observing the Eight Burst is its southerly declination of −40°. But even when low on the horizon this one is worth catching, so give it a go.

    Hubble Image of the Eight Burst Nebula
    ngc3132_hst_935.jpg

    Discovered by Sir John Herschel at the Cape of Good Hope in 1835 with an 18-inch speculum telescope, it was originally cataloged as h3228. Herschel’s discovery log entry reads: “Planetary nebula, very large, very bright, elliptic; has in it a 9th mag star somewhat excentric. Its light is exactly equable, ie. not increasing towards the middle; yet I cannot help imagining it to be closely dotted. It is just like a star out of focus in certain states of the mirror and atmosphere. Three stars near, a = 9th mag; b = 9th mag; c = 14th mag; A very extraordinary object."

    H. Shapley and J. S. Paraskevopoulos in “Photographs of Thirty Southern Nebula and Clusters” coined the name Eight Burst Nebula in 1940. Concerning the planetary nebula they say: “A series of photographs of varying exposures would be necessary to bring out the intricate details…. It could well be named the “8-burst” planetary from the number of distinct arcs on the boundary of the main disk or shell”.

    Plate III Figure 13 from Lassell, W. (1867) Miscellaneous Observations with the Four-foot Equatorial at Malta. Memoirs R.A.S., 35.
    ngc_3132_lassell_1867_3_13.jpg

    Unusual among the planetaries is the prominent white 10th magnitude central star. This star is also a known binary, having a 16th magnitude companion, ~1.6" away. Studies show that it is this star, and not the 10th magnitude primary that is responsible for illuminating the nebula. Simply, the presumed progenitor does not produce enough ultraviolet to illuminate the gas. The planetary nebula nucleus is a bright example of the Wolf-Rayet class of stars, having a surface temperature around 135,000°! The nebulosity comprises of a H/He ratio of 12.7%, and an excess of Nitrogen that is higher than most of the other planetaries known. This suggests that the mass of the star was originally about 2.4 Solar Masses, at the lower limit for stars that can produce planetary nebulae.

    The Eight Burst Nebula is extremely bright – even for small telescopes in light polluted skies. However for those observers in more northerly latitudes the window of opportunity for observing the planetary is rather limited. Here at 40°N the Eight Burst Nebula is best observed in March and April when it culminates at ~10° above the horizon. That time is rapidly approaching as today’s (March 16, 2014) Full Moon begins to wane towards New Moon on March 30, 2014.

    DSS POSS-2 Red Plate FOV 15x15 arc minutes
    ngc_3132_15x15_poss2red.jpg

    Here’s some observation notes from March 2012 through a 17.5” f/ 4.5 reflector. SQM 20.45. “Initial reaction is this is a twin of the nearby Ghost of Jupiter. Large, size is 1 arc-minute. It has a ghostly appearance yet it is surprisingly bright. Somewhat elongated with a clearly defined ring structure. Prominent central star estimated to be Mag 8.”

    While researching I found observations of the Eight Burst Nebula made through a wide range of apertures, with the smallest being a 102mm refractor. Of course some observers have a distinct advantage of higher elevation, and/or a more southerly latitude which places the nebula higher in the sky. With an aperture of greater than 12” most reported seeing color (blue or green) and some structure detail within the nebulosity. OIII filters were reported to provide a good improvement.


    “GIVE IT A GO AND LET US KNOW”
    GOOD LUCK AND GREAT VIEWING!
    Last edited by deepskytraveler; March 17th, 2014 at 10:28 AM.
    Clear Skies,

    Mark Friedman
    Wheaton, IL USA

  2. #2
    Member Clear Skies's Avatar
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    This planetary shows a bit of detail even in very small telescopes. Observed it in 2008, using a small "travel Mak" when I first visited Sutherland, South Africa. @106x I could clearly see its ring structure, elongated north to south. No color though in the 5" scope. I estimated the superimposed star, not being the central star, to be mag. 9-ish.

    CSOG Screenshot:
    Victor van Wulfen

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    This object is unfortunately too low to be visible from Finland but I had a good chance to observer this in Australia four years ago. The observing conditions weren't perfect because of the crescent moon on the east sky. Despite of that 10" newton showed an elliptical ring which had brighter parts on the east and west sides. The central star and central area appeared "hazy".

    Newton 254/1200 mm @ 478x
    Iiro Sairanen, Finland
    --> http://deepsky.arkku.net <--

    N18" F5, N12" F5, N4.3" F7.3

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    Member Ivan Maly's Avatar
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    Observing from Australia with 5.5" at 90-270x, I recorded: "The slightly elongated ring and the bright central star could be seen clearly. O’Meara mentions that the true (illuminating) central star is a faint, close, and probably true companion of the visible one."
    Ivan
    20" Sky-Watcher
    deepskyblog.net

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    Unfortunately NGC 3132 is not visible from Central Europe (ok, from my southern most observing place it runs 2° above the horizon) but from southern latitude for sure the best PN in the sky beside NGC 5189.

    I had the luck to observe this guy several times from Namibia (23°S). The 12" shows a lot of detail like it is shown in the sketch below.

    12", 375x, no filter, fst 7m+
    NGC3132.jpg
    Clear Skies, uwe
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    27" f/4,2

  6. #6
    Member Marko's Avatar
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    My best description of this comes from 4/6/2010 in an 18" both with OIII filter where I state the central star was averted only so I am certain I did not look at it unfiltered (sadly).

    NGC 3132 Type: Plan Position: 10 07 01.8 -40 26 09 Con: Vel
    Date: 04/06/10 Time: 21:40 Site: DinoPoint
    Scope: 18Sm3.7Pc Eyepiece: 7mmNag Power: 278
    NELM: 6 SQM: 21.15 Seeing: 4 Transparency: 3
    Description: 'EightBurstNebula: OIII filter. lt 1' 1.3EL 150dPA Middle
    star only with averted. Very slight dimming around central star.
    Mostly an even disk. Possible slight bump in NW edge. :: 5mmNag
    389x OIII shows Central darkness of 1/4 diamiter. Sticks out
    little bit on NW edge. Also on SW side seems like a bit of a
    bump. NE edge has a bit less glow on this side.'
    Let me roam the deep skies and I'll be content.
    Mark Johnston
    18" StarMaster f/3.7
    12" Meade LightBridge f/5

  7. #7
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    I was finally able to observe this planetary nebula from my SQM=19.1 backyard in La Serena, Chile, using my 12" dob. My notes read:

    At 43x already visible as a fuzzy star. At 188x a central star surrounded by an oval glow. The star doesn't lie exactly in the middle bus is displaced east along the major axis of the oval. Some dark features are barely visible in the disk. At 319x the disk seems to be open at the west side. Closer inspection reveals a very thin edge with a dark gap between the edge and the central star. Occasionally a dark gap appears between the central star and a thin, east edge.

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