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!
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