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View Full Version : Object of the Week January 10th, 2016 – Palomar 2



Uwe Glahn
January 10th, 2016, 06:15 PM
Palomar 2 (= C 0443+313) [= MCG +05-12-001; PGC 15963]

Constellation: Auriga
RA: 04h 46m 06s
Dec: 31° 22’ 53”

Type: Globular Cluster, Class IX
Distance (Galactic center): 111000 ly
Distance (sun): 85000 ly
Size: 1.9’
Mag: 13.0V
Brightest Star: 18.0V

The OOTW type for the early winter season is as unusual as its location in the sky. In the SE Auriga region – between the Pleiades and Messiers famous Auriga cluster Palomar 2 is the only object of that type in that part of the sky.
But unusual not only in our perspective – Pal 2 located farthest on the sky from the Galactic center, even under all other “outer halo clusters”

But let’s start at the very beginning. A.G. Wilson discovered one unknown object on the plates of the 48-inch Schmidt telescope of the Palomar Observatory in early 1955. A little bit later, G.O. Abell listed and published a list of all in all 13 newly discovered globular clusters in late 1955 [1955PASP...67..258A (http://adsabs.harvard.edu/abs/1955PASP...67..258A)].

Because of its unusual orbit the cluster is highly obscured by dust. The immersive foreground reddening of around 1,2mag (B-V) made it very difficult to study. Modern studies with the 3,6m CFHT (http://www.cfht.hawaii.edu/) on the top of the Mauna Kea gave a more or less detailed picture of Palomar 2. [1997AJ....114.1043H (http://adsabs.harvard.edu/abs/1997AJ....114.1043H)] The photometry gave an intermediate metallicity and a distance of about 34kpc from the Galactic center.

From the observation standpoint Palomar 2 belongs to a difficult candidate of the catalog but not to an impossible object. Under dark and transparent skies a mid size telescope should show the GC. Perhaps also a smaller telescope could show something when all things around fits perfect. My notes from my Palomar Project (http://www.deepsky-visuell.de/Projekte/PalomarGC_E.htm) say:


8", 80x, NELM 6m5+ - nothing with 31x and 47x; with 80x a stellar spot is visible with averted vision at the position of the GC; not sure if the plob was the GC or the glow of the 2,3' NE 13mag star
16", 225x, NELM 6m5+ - faint GC, can hold it with averted vision; round; concentrated to its middle; diffuse edges; no stars
16", 129x, NELM 7m0+ - easier to detect than Pal 1, circular, concentrated to its middle, no stars, structureless
27", 172x, NELM 7m0+ - easy to detect; steadily with direct vision, concentrated, round plop, no stars or mottling (bad seeing)


1957
DSS blue 30'x30'

1958
NASA/ESA HST (https://www.spacetelescope.org/images/potw1315a/)

1959
16", 129x, NELM 7m0+ (http://www.deepsky-visuell.de/Zeichnungen/Pal2.htm)

As always, give it a go and let us know.

Steve Gottlieb
January 11th, 2016, 12:54 AM
My last 18" observation of Pal 2 is quite similar to your 16" notes. What have others seen?

Pal 2 was immediately picked up at 285x as a faint, fairly small, roundish glow, ~1.5' diameter. Easily visible with averted vision and could be held continuously without difficulty. Very weakly concentrated with a very small brighter core or knot that seemed offset from the geometric center. SQM-L 21.55

KidOrion
January 11th, 2016, 02:39 AM
I've only looked for it once with any seriousness, but that was on a night with extremely poor seeing. I had always assumed it to beyond the scope of my 12.5" Dob, although evidently a number of others have seen it in scopes that size. I've logged several other Palomars (13, 12, 9, 8, and 7) and a Terzan (7), so I'll have to keep after Palomar 2.

lamperti
January 11th, 2016, 12:11 PM
Saw it with a 20" at 272x. It makes an equilateral triangle with 2 stars, with Pal-2 at the apex. Not quite resolvable. Hazy patch.

I wrote an article on all Palomar GCs in The Deep Sky Observer 154:22-25, 2011

Jim Chandler
January 11th, 2016, 12:42 PM
My note from December 2004 using a 25" f/5 at 287x:

As the seeing comes & goes, the view changes from nebulous to granular. A compact, almost circular cluster.

akarsh
January 11th, 2016, 11:32 PM
I had one negative observation at Texas Star Party 2012.

And positive observation on Nov 3 2013, observed right around culmination.
My notes say that it was best viewed at 205x and sported very very inconspicuous hints of resolution. My notes also claim that it was "surprisingly easy", which only means that I had expected it to be nearly impossible, but it was not. Unfortunately, my logging skills are only slowly improving, and I certainly didn't make good logs in 2013, so that's all I have :P

Clear Skies

Regards
Akarsh

mdstuart
February 14th, 2016, 11:30 AM
I had a go with my 16 inch scope at this one. I could see one of the two stars left of the globular cluster in the DSS blue image above but I could not say I definitely observed Palomar 2.

At times with averted vision I thought I could see something but not enough to confirm it.

My skies at the time were mag 5.5 and I could see stars to mag 14.5.

I will try again!

However I did manage to spot six galaxies in the same FOV in the NGC 3158 group on the same night so not too bad a night.

Mark

KidOrion
February 14th, 2016, 06:25 PM
90% certain I picked this one up on 02/08. I didn't take "real" notes on it, but it was a threshold-dim glow, somewhat larger than I had expected (so about 1' or so). It took averted vision, rocking the scope, and lots of staring into the field to see it. Another experienced observer verified that he saw the same thing that I did; I still won't consider it a "legitimate" observation until I've seen it again, and probably sketched the field.