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Thread: Object of the Week December 25, 2016 - Polarissima Borealis - NGC 3172

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    Member deepskytraveler's Avatar
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    Object of the Week December 25, 2016 - Polarissima Borealis - NGC 3172

    Object of the Week December 25, 2016 Polarissima Borealis

    Polarissima Borealis, NGC 3172, PGC 36847, MCG 15-1-11
    Type: Spiral S0 nearly face-on galaxy
    Constellation: Ursa Minor
    RA: 11h 47m 12.1s
    Dec: +89° 05' 36"
    Magnitude: 14.8 B
    Mean Surface Br: 23.0 Mag/arcsec²
    Size: 1.1' x 1.0'

    PGC 36268, MCG 15-1-10
    Type: Spiral?
    Constellation: Ursa Minor
    RA: 11h 40m 40.2s
    Dec: +89° 05’ 6”
    Magnitude: 16.0 B
    Size: 0.45’ x 0.35’

    While celebrating Christmas this year, my first as a grandfather, I decided it might serve me well for future Christmases to brush up on the legend of Jolly Old Saint Nicholas, more commonly known as Santa Claus. Besides this would be a good activity for cloudy nights, which much to my chagrin are way over abundant this time of year in Ohio.

    As I began to recall the Santa stories from my youth, I distinctly remembered that Santa Claus and his elves lived and worked in a place known as the North Pole. Well I began thinking that to produce Christmas presents for planet Earth’s population of 7.4 billion people it would require a very, very large number of elves; for the sake of this story let’s just call it a horde of elves. So this North Pole place needs to be large enough to accommodate living and working quarters for Santa and his horde of elves. Oh where, oh where might this North Pole place be? I turned to Google to locate the North Pole home and workshops of Santa Claus. However I was dismayed to learn there were many North Poles all claiming to be Santa’s home town. Here is a brief rundown on a few of the top contenders.

    The terrestrial or geographic North Pole is located at latitude 90° 00' 0.00" N and longitude 0° 00' 0.00" E. This area is nothing but a frozen sheet of sea ice located in the middle of the Arctic Ocean. Not surprising that neither Santa nor his horde of elves would live there. Next, the North Pole location cited as the “official” home town of Santa Claus - Rovaniemi, the capital of Lapland, in northern Finland. Other locations pretending to be the residence of Santa are: North Pole, Alaska 99705; North Pole, New York 12997; and Santa Claus, Indiana 47579.

    Regardless of their claims, none of these locations are large enough IMHO to support Santa’s horde of worker elves. Confused and frustrated I continued to ponder and ponder. Then much to my surprise, just like a supernova, a light bulb popped on in my head. Through the eons of telling the Jolly Old Saint Nicholas legend and passing it from generation to generation a simple, yet most crucial word had been lost. It was not the Terrestrial North Pole that I was seeking. That lost word - it was Celestial. I needed to be looking at the North Celestial Pole (NCP). My search was now too big for Google; this was a job for MegaStar!

    Filled with an air of anticipation I rushed to my computer and into MegaStar. Quickly I located Polaris (Alpha Ursa Minor) or more commonly the North Star – which I knew to be situated in close proximity to the North Celestial Pole. From there I mooz’ed (if you don’t know, don’t ask) until I beheld the object of my quest, Polarissima Borealis.

    Polarissima Borealis, a long forgotten galaxy, yet ever so close to the North Celestial Pole. I knew immediately this was the true home for Santa Claus and his horde of elves.

    This galaxy was discovered by John Herschel in October 1831 using an 18¼ inch reflector. He cataloged it as JH 250 in the Slough Catalog; Slough being his home and observatory in Slough England. The only discovery notation by Herschel that I was able to find was a single word, “Polarissima.” It was John Dreyer who later cataloged this galaxy as NGC 3172 with the following notation "very faint, round, gradually brighter middle, 11th magnitude star 2 arcmin to south, Polarissima Borealis." Polarissima Borealis is Latin for “very north polar”, the appellation referring to the fact that it was the northernmost non-stellar in the sky at that time.

    ngc3172.jpg
    The NGC / IC Project

    Today Polarissima Borealis is 0.9° from the NCP. Although there are a few magnitude 17+ galaxies in the neighborhood that might be a smidgen closer to the NCP; Polarissima Borealis remains the northernmost NGC/IC object as well as the brightest deep sky object near the NCP.

    Location accolades aside, Polarissima Borealis is rather nondescript galaxy in the constellation Ursa Minor. It is 303 million light years from our solar system. Polarissima Borealis appears roughly 1.1 x 1.0 arcminutes in size, corresponding to a physical diameter of 101,356 light years. It is a spiral galaxy of morphological type S0, and is receding at 6,096 kilometers per second - about 2.0% of light speed.

    A survey of the research on Polarissima Borealis yields very little material – it is not a much studied galaxy. The only exception being the occurrence of Supernova 2010af in March 2010. That supernova blossomed from an unseen progenitor of magnitude greater than 20+ to a magnitude of 17.2 and was classified as a type Ia supernova.

    N3172-SN.JPG
    2010af, CBET 2194 discovered 2010/03/04.808 by Tom Boles

    To observe Polarissima Borealis with any detail requires moderately large aperture in combination with very good seeing and transparency. Observers have reported positive observations of the galaxy in scopes as small as 4.3” (non-stellar glow with averted vision) and with 8” under NELM 6.2 magnitude skies (extremely faint). Not until you hit 12.5” of aperture, and then under very dark skies with better than average seeing and transparency, will you be able to discern any detail in the galaxy. With my Obsession 15 under SQM-L 18.6 = NELM 4.5 suburban skies, the galaxy was “detectable as a very faint, small round fuzzy patch, mostly homogenous, perhaps very slight brightening discernible towards core, no discernible mottling or spiral structure.” I expect that with scope apertures of 18” or greater Polarissima Borealis might yield some of its detail. A distinct observing advantage with this galaxy is that it is visible every clear night of year for observers in the Northern Hemisphere.

    For those of you with 30” or larger scopes a challenge object is PGC 36268. This galaxy is immediately adjacent to NGC 3172. It has an apparent size of 0.45’ by 0.35’. Based on faint extensions surrounding NGC 3172, PGC 36268 may be interacting with it. Whether it is actually a companion of the larger galaxy or merely an optical double is unknown.

    n3172wikisky.jpeg n3172photometry.jpg

    In Christmases of the future I will share the legend of Jolly Old Saint Nicholas with my grandchildren. When the question is asked about where Santa and his horde of elves live and work, we will go outside on a clear night and through the telescope I will show them Polarissima Borealis, the true home of Jolly Old Saint Nicholas.

    Give it a go and let us know!
    Last edited by deepskytraveler; December 31st, 2016 at 04:25 PM.
    Clear Skies,

    Mark Friedman
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    Member Ivan Maly's Avatar
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    It looks like a near-face-on S0. At 225x in 16" under 21.6 mag/arcsec^2 skies, one fine summer night I recorded NE-SW elongation, smooth concentration, and glimpses of a starlike nucleus. So it probably beats the North Terrestrial Pole by the length of the description that I can render.
    Ivan
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    Member RolandosCY's Avatar
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    Mark, superb writing! Amazing! Well done! As for Polarissima itself, I have observed it with my 18" from SQM 21.6 skies on a very clear but not so steady night in July 2015. I don't have the observation handy now, but I recall a rather faint, roundish - ovalish spot. There must be more details but I need to see the drawing for that!
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    Member Howard B's Avatar
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    Jimi and Steve G and I had a look with the 48 inch this past October:

    "Polarissima - bright and easy and its companion was also easy to see but fainter. The nearby edge on MAC was barely seen, but a few times I (could) see its orientation. 610x, 21.34 SQM."

    N3172_Polarissima_crop.jpg N3172_Polarissima_cropinvert.jpg

    Had we realized this is really where Santa's workshop is located we would have looked more closely!
    Howard
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    Member Steve Gottlieb's Avatar
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    Here are the notes I took on NGC 3172 and its two companions through the 48". PGC 36268 was easy, but the edge-on 2MASX J11503836+8907109 was a stinker. It shows up very faintly in the DSS image that Mark posted (from the NGC/IC Project)

    48" (10/26/16): at 375x and 488x; fairly bright, moderately large, round. Sharply concentrated with a very bright round core that increases to the center and a low surface brightness 45" halo. A mag 12.5 star is 1.5' separation (NW) and a mag 16-16.5 star is within 1' (50" S).

    MCG +15-01-010 = PGC 36268, at 1.5' separation (WSW), appeared fairly faint, fairly small, ~35" diameter, slightly elongated, weak concentration. Visible continuously with direct vision though fairly low surface brightness. A mag 16.7 star is 16" W.

    2MASX J11503836+8907109 = LEDA 3777919, at 1.8' separation (NNE), appeared extremely faint and small, ~6" diameter. A mag 15.7 star is 25" away. At 610x, the galaxy popped as a thin, low surface brightness edge-on, ~20"x6".
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    Great choice Mark. I took an attempt last new moon under very good transparency and have to say - worthwhile object.

    To the companions. I noted:
    - PGC 36268 (= MCG+15-01-010): direct vision, round, concentrated, faint star within the halo
    - PGC 3777919 (= 2MASXJ11503836+8907109): not steadily visible, can hold stellar glow for a few seconds each, no elongation visible

    And I think I got a third companion from which I found no entry in the LEDA. While trying to see as much stars a possible I noted a faint double star 2,6' SW of the core of NGC 3172. In the POSS the N component looks like a galaxy. Did anyone tried this object or has a confirmation for that?

    Second interesting feature was the huge size of the galaxy itself when using lowing magnification.

    27", 172x-419x, NELM 7m0+, Seeing III
    NGC3172.jpg
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    Member deepskytraveler's Avatar
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    The attached SN2010af verification image is one of the better images I came across of Polarissima Borealis and its companion/neighboring galaxies. I added annotations for PGC 36268 and 2MASXJ11503836+8907109 as described by Steve and Uwe. I also circled two other objects that are looking to be galaxies. Thoughts? Identification?

    From my perspective this image clearly shows the spiral structure of NGC 3172. It also appears that PGC 36268 has distorted the adjacent area of 3172. Although the 2MASX galaxy also appears to be within an arm of 3172, I'm thinking it is just a visual alignment.

    N3172-SN copy.JPG
    Clear Skies,

    Mark Friedman
    Wheaton, IL USA

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