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Thread: Object of the Week September 21, 2014 The Propeller Galaxy NGC 7479

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    Member deepskytraveler's Avatar
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    Object of the Week September 21, 2014 The Propeller Galaxy NGC 7479

    Object of the Week September 21, 2014 The Propeller Galaxy NGC 7479

    NGC 7479 UGC 12343 PGC 70419 MCG +02-58-60 The Propeller Galaxy
    nearly face on barred spiral galaxy (SBbc)
    RA: 23h 04m 56.7s Dec: +12° 19′ 22″
    Size: 3.7’ x 2.8’
    Mag: 10.8v
    Mag: 11.7B

    In his OOTW contribution last month, Paul Alsing described The Propeller Nebula, Simeis 57. So this month I couldn’t resist sharing its galaxy namesake The Propeller Galaxy, NGC 7479.

    William Herschel discovered NGC 7479 in 1784 with an 18.7-inch f/13 speculum telescope. It was originally cataloged as H I-55. In his discovery notes Herschel called it “considerably bright, much elongated in the direction of the meridian, gradually brighter in the middle, 4’ long, 2’ broad.”

    n7479ngcic.jpgn7479blk.jpg

    Admiral William Henry Smyth in The Bedford Catalog, From A Cycle of Celestial Objects (1844) had the following to say after observing the galaxy in a 5.9-inch refractor, “This is very faint but after long gazing under clockwork motion, it comes up, trending nearly north and south, have a telescope star at each extreme. Now, the sphere being the general figure assumed in consequence of the particles mutually attracting each other, we can only suppose that the lenticular appearance before us, is a vast ring [of stars] lying obliquely to our line of vision.” What an incredible supposition given the state of astronomical knowledge and telescopes in the mid 19th century.

    ngc7479hst.jpg

    NGC 7479 belongs to the Pegasus Cloud, which contains 51 galaxies. It is a visually and photographically striking galaxy. It is located about 3° south of Alpha (α) Pegasi, or Markab, the southwestern corner of the Great Square. Moderately bright at a visual magnitude of 10.8, you should be able to detect the galaxy in scopes as small as 4 inches under reasonable dark skies. In fact The Propeller is an excellent example of what larger aperture and darker skies can do – showing a progressive increase in detail. In smaller telescopes NGC 7479 appears as a very faint elongated fuzzy patch. With a moderate increase in aperture the galaxy’s bar begins to materialize; likewise a tiny core becomes apparent. As the aperture increases so does the amount of detail in the arms and the core. The spiral is highly asymmetrical with the dominant feature being its inverted S, which spins in an anticlockwise direction. The westward curving spiral arm is sharply defined, while the other arm is less define, appearing like a frayed rope. Be sure to explore the spiral arms and the core at high powers. The latter has been reported to show structure under exceptional seeing.

    ngc7479-lum.jpgNGC7479HW.jpgNGC_7479_copy_385x344.jpg

    The beauty of NGC 7479 extends beyond the visual. At radio wavelengths the arms spin the other way, in a clockwise direction. Studies demonstrate that this radio jet was put into its bizarre backwards spin following a merger with another galaxy. In the course of my research on The Propeller Galaxy one paper I found fascinating was A minor-merger model for NGC 7479 by S. Laine and C.H Heller, which describes a numerical simulation model for the overall morphology of the galaxy that is based on a minor galactic merger.

    Star formation is reignited by galactic collisions and NGC 7479 is undergoing starburst activity. It is recognized as a Seyfert II galaxy with an active galactic nucleus. In a 1999 Astrophysical Journal Supplement Series paper Rosa Gonzales Delgado (Space Telescope Science Institute) reported the discovery of 86 H II regions in the galaxy’s two main spiral arms. Supernovae 1990U and SN20009jf occurred in NGC 7479. The former was a Type Ic supernova, a massive star that self-destructed after ejecting its outer envelope of hydrogen and helium.

    You'll find sketches of NGC 7479 by Deep Sky Forum members here.

    Hope you enjoy The Propeller Galaxy.

    “GIVE IT A GO AND LET US KNOW”
    GOOD LUCK AND GREAT VIEWING!
    Last edited by deepskytraveler; September 28th, 2014 at 05:25 PM.
    Clear Skies,

    Mark Friedman
    Wheaton, IL USA

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    Hi,

    A very nice object, also in small telescopes. In my 6" I have seen the central bar and the bar curling to the west. In my 20" this galaxy is a very beautiful barred spiral, though the north and east arm is very low surface brightness and hard to see.


    Clear skies,

    Wouter van Reeven

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    Member Clear Skies's Avatar
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    An observation in October 2013 from a dark site, 12" SCT 179x/27' and 254x/19':

    17mm TeleVue Nagler Type 4: A beautiful galaxy, very elongated north to south when not using AV, using AV the outer parts brighten and the southern arm towards the west is visible very faintly (little more than a brighter background, only the start of the arm is visible). The outer halo is faintly visible to the east and NE, without detail. Centrally the galaxy is brighter with a clear, round, brighter central part. The galaxy is brighter to the SSW of the center and fainter to the NNE. On the NNW edge, almost due north is a mag. 12 star, WSW of the center (closer to the center than the mag. 12 star is) is a mag. 13.5 star.

    12mm TeleVue Nagler Type 4: Using this magnification the faint outer parts of the galaxy fade away and only the brighter central part remains clearly visible.

    Rated it 7/10.

    An observation in 2007 using an 8' SCT under light polluted Dutch skies revealed only an extremely faint, elongated streak: the galaxy's bar.
    Victor van Wulfen

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    Member Ciel Extreme's Avatar
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    This has always been a favourite of mine, which I have observed many times with 8-inch, 15-inch and 18-inch telescopes. Regrettably, the spiral arms are very faint compared to the bar and difficult to see. The best I’ve ever been able to do was detect a faint haze surrounding the bar. I’m attaching a sketch I made last year. Perhaps someone with better visual acuity than mine would be able to detect the spiral structure with an 18-inch, though I think scopes in the 24-inch range and up would have more success.

    NGC7479.jpg
    Mark Bratton
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    “The Complete Guide to the Herschel Objects” (CUP 2011)

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    Revisited this galaxy with my friends 25" LOMO under an fantastic sky and what a wonderful galaxy. Both arms direct vision.

    With 16" the SW arm was visible without problems but the NE arm was pretty tough even under very good transparency. And don't forget - Palomar 13 stands only 0,6° NE.

    16", 257x, NELM 7m+


    16", 51x, NELM 7m+
    Clear Skies, uwe
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    27" f/4,2

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    Member Ivan Maly's Avatar
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    The best view I have had with my 16" included the split in the northern arm and the dust lane in the bar. There was a compact enhancement within the elongated enhancement in the S arm.

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    Member Howard B's Avatar
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    Here's an observation of 7479 with my 28 inch and another with Jimi's 48 inch -

    28 inch:
    "Close to PAL 13 so I popped over for a look and found this great view! Both spiral arms are seen without much effort, and if memory is accurate this beats some views I've had of 7479 from the OSP - but then it is is 2:14 am... 408x, 21.39 SQM."
    N7479_fromChucksPlace.jpg N7479_fromChucksPlace_invert.jpg

    48 inch:
    "No dark lane in the fainter arm, but I did get one hit of it. Magnificent view otherwise. 7mm (696x) 21.51 SQM." Note that I saw two bright spots in the brighter arm, which I'd never suspected before.
    N7479_48inch_sketch.jpg N7479_48inch_sketch_invert.jpg
    Howard
    30-inch f/2.7 alt-az Newtonian
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    Member RolandosCY's Avatar
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    Last Monday night I was under very dark (SQM 21.55) and steady skies at my favorite site (Paradisos Hills Hotel terrace!) in Lysos, Cyprus. Need;ess to say NGC 7479 was high in my observing list. Amazingly, my only previous observations of this spiral were made with my 4" refractor from a similarly dark site years ago, and with my 6" achro a few weeks ago from my SQM 21 backyard. In both cases the galaxy was logged as "spindle shaped, somewhat brighter in the center". With my 6" at very high power (257X) I noticed a very faint glow surrounding the brighter spindle.

    From Lysos though, with the 18", the galaxy was dramatically transformed. I could readily see that what appeared like a barely detectable glow in the 6" was really the light from the two spiral arms. Like the other observers above, I noticed that the SW arm was clearly visible, shaped like a scimmitar, with a faint star between it and the core of the galaxy. What amazed me more was that this arm appeared quite thin but very well delinated, and seemed to be embedded in a slight haze. The NE arm was not as defined. It seemed thicked then the SW arm, turning off the core just before a faint star, but unlike the aother arm, I could not really follow it all the way to abeam the core. It seemed to disappear into a general haze right at the 180-degree turning point. I kept staring at the galaxy for quite a while, and at times I had the impression that I could see the arm continuing further, but I could not really hold it. The "frayed rope" appearance mentioned by Mark really fits what I observed.

    7479Neg1a.jpg 7479a1.jpg
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    IDSA names this galaxy Superman Galaxy. Would anyone know who coined that name?


    Thanks and clear skies, Wouter

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