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Thread: Object of the Week Feb 18th, 2018 - NGC 2371/72, the Double Bubble planetary

  1. #1
    Member Steve Gottlieb's Avatar
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    Object of the Week Feb 18th, 2018 - NGC 2371/72, the Double Bubble planetary

    NGC 2371/2372 = PK 189+19.1 = PN G189.1+19.8
    RA: 07h 25m 33.8s
    DEC: +29° 29' 18"
    Type: Planetary Nebula (bipolar)
    Size: 74"x54"
    Mag: V ≈ 11.2

    William Herschel discovered this unusual planetary in 1785 with his 18.7-inch speculum reflector and reported a double nebula, resulting in two NGC designations. On March 12th 1785 (his 385th sweep) he described "Two [nebulae]. Faint, of an equal size. Both small within a minute of each other; each has a seeming nucleus, and their apparent atmospheres run into each other. 240x showed the same position from south-preceding to north-preceding." He published a sketch in an 1811 paper as an illustration of "double Nebulae with joined Nebulosity."

    In February 1827 John Herschel called NGC 2371 "the south-preceding of a curious bright double neb or an elongated bicentral neb; nuclei approaching to stars 45° nf or sp - distance of centre 60"." In December 1848 Lord Rosse made a sketch using his 72" and found a "bright star between, tails and curved filaments, perhaps an annulus round the two nebulae."

    Based on a Crossley photograph, Heber Curtis (1918) described NGC 2371-2 as follows: "Brightest portion consists of two lobes which together form an irregular and patchy oval. The brightest part of these lobes are 35" apart in pa 65°; the toal diameter in this direction is 54". Two very faint, curved outliers are each 60" distant in the prolongation of the major axis in pa 126-306°. A narrow vacant lane runs between the lobes, nearly in the major axis, and widens to include the central star."

    NGC 2371/72 is an excellent example of a bipolar planetary, with two symmetric lobes straddling a hot central star. In fact, it's a bit surprising this excellent planetary hasn't been featured before in an OOTW!

    NGC 2371.jpg

    A 4-inch scope reveals a small, hazy patch 3° southwest of Castor while an 8-inch will resolve Herschel's twin bubbles. In my 18-inch, the bright lobes slant southwest to northeast and both span 15" to 20" in diameter. At 380x unfiltered, the southwest lobe appears brighter and the faint 14.9-magnitude central star is visible at the midpoint. A weak bridge of nebulosity connects the two lobes giving a "dog bone" appearance and a halo encases the structure.

    Through my 24-inch, two detached ghostly "polar caps" or ansae can be glimpsed 1' northwest and southeast of the central star, on a line perpendicular to the major axis of the two primary lobes. In excellent conditions the outer wings are barely visible through an 18-inch scope, though the northwest wing is a bit brighter and may be the only one seen.

    Back in April 2011 I was wowed by the view through Jimi's 48-inch. Here are my notes --

    There was so much intricate detail in NGC 2371/72 it had little resemblance to previous views through my 17.5" and 18" scopes. The most prominent feature was two, irregularly round, very bright nodules on the southwest and northeast side of the boxy, elongated central region. Each nodule was distinctive and varied in surface brightness and shape with the southwest lobe brighter. Filamentary streamers or a "hairy tail" extended from the northeast node towards the northwest and similar wisps extended mainly southeast from the southwest node, creating a sense of rotation around the fairly bright central star. The interior and sides were filled with much fainter nebulosity. A very faint filament connected the main lobes on the northwest edge. Detached from the main 1' structure were two amazing outer wings, symmetrically hanging 1' NW and 1' SE from the central star. These wings or "polar caps" were easily visible without a filter at 488x and both extended ~40"x10" in a SW-NE orientation, increasing the total diameter of the planetary to 2'. A mag 13.5 star lies 1.5' NW and a mag 16 star is 50" NE of center.

    This HST image reveals interior details and jets in the main lobes (the elongated pink knots), which were ejected symmetrically from the central star. The brighter one may be visible as a brighter spot in the main southwest lobe.

    NGC 2371_HST.jpg

    Give it a go and let us know!
    Steve
    24" f/3.7 Starstructure
    18" f/4.3 Starmaster
    Adventures in Deep Space
    Contributing Editor, Sky & Tel

  2. #2
    Hi All,
    Here my drawing of this PN, with a 25" obsession.

    NGC 2371 T635 BL 2017 04 19.jpg

    Observation report is here: http://www.deepsky-drawings.com/ngc-2371-2/dsdlang/en
    And a comparison with an older one: http://www.deepsky-drawings.com/ngc-...017/dsdlang/en

    Clear skies
    Bertrand
    http://www.deepsky-drawings.com/dsdlang/en/

  3. #3
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    Hello Steve,

    indeed a nice one - one of my favorite pn. In my 12" at powers around 300x central star never was a problem - due to common good seeing at my sites i guess.

    Last season i checked the halo fragments - without knowing exact position. Without filter i could easily detect a longish patch at a spot what later confirmed to be the "curved outliner" at pa 306. The second one i could not detect. Power might have been 170x. Altitude 5000 above sea level, NELM around 7m+

    CS
    Norman
    12" f/ 4,5 - tuned Sumerian Optics Dobson - Nauris main mirror
    - who stands the rain deserves the sun! -

  4. #4
    Member Howard B's Avatar
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    Excellent choice Steve! My most detailed observation of NGC 2371-72 is from February 2, 2005 with my 28-inch:

    "Holy cow - smoke, whatever, this is a fabulous view of a bi-polar nebula! My goodness, the detail is amazing, especially the two faint wings to either side. The "sprinkler effect" is strong in this view, it really looks like this thing is spinning and throwing off the nebulae. Very cool - even has a bright central star. 654x."

    N2371_2372_crop3.jpg N2371_2372_crop3_invert4.jpg

    Even though this observation was made 13 years ago I remember the night well. Myself and two friends were at a site in the Oregon Coast range at around 1000 meters altitude, and although there was considerable air glow the seeing was quite sharp. We were on a ridge and were only about 30 meters above the fog bank below us, and watching the fog slosh back and forth for several hours, almost but never quite getting to our position, was as mesmerizing as anything we saw in the sky that night.
    Howard
    30-inch f/2.7 alt-az Newtonian
    https://sites.google.com/site/howardbanichhomepage/
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    Contributing Editor, Sky & Telescope magazine

  5. #5
    Co-Founder DSF.com Jimi Lowrey's Avatar
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    This is one of my favorite PN. I did not know of the jets something new to try for in the future.
    Clear Skies,

    Jimi Lowrey
    Fort Davis Texas

    48"F4 OMI/TEC
    28'F4 ATM

  6. #6
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    Indeed Steve, one of the beauties out there.

    I attached some observation within the last years.

    4", NELM 6m5+
    difficult object; not visible in the searching eyepiece; with 88x and without any filter faint, round patch; with [OIII] bipolar structure suspected

    8", NELM 6m5+
    faint object in searching eyepiece; from 80x up two small plobs clearly visible with the SW one clearly brighter; with 228x both knots easy to separate; no CZ visible

    12", 300x, NELM 7m0+
    under good seeing the CZ appears faint, but is visible with averted vision for seconds each

    16", 280x, NELM 6m5+
    two easy visible knots which seems to be a little bi structured; especially the fainter NE plob shows a hook away from the brightest point; with [OIII] the brighter outer halo fragment to the NW is popping in and out of view
    NGC2371_NGC2372.jpg

    16", 280x, NELM 7m0+
    concentrated observations now shows both outer halo fragments, NW fragment looks brighter

    24", 300x, NELM 6m0+
    both outer halo fragments visible, both could be hold steadily with averted vision

    27", 293x, NELM 6m5+
    both outer halo fragments easy visible with direct vision through [OIII] filter, even visible without any filter; PN shows absolutely negative response to Hß, even the both bright knots disappears
    Clear Skies, uwe
    http://www.deepsky-visuell.de
    Germany

    27" f/4,2

  7. #7
    Member Daniel_Sp's Avatar
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    Hi,
    to me, this PN is not that spectacular.... Sorry, but it's not one of my favorites. Here is my sketch from January 2011, made with 12" at 208x with [OIII]-filter
    2371_2372_cutj.jpg
    24"-Dobson, f/4.16

  8. #8
    Member Ivan Maly's Avatar
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    My notes from 2010 say, "binary glow oriented from NE to SW". 4", 70x, average 21.6 mag/arcsec2 site.

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