Object of the Week September 8, 2013 - G 1 and a few other Super Size Clusters

[Jimi Lowrey]

G1 AKA Mayall II

Andromeda

RA
00 32 46

DEC
+39 34 41

MAG 13.2

Type Globular Cluster?-- UCD (Ultra compact dwarf)?-- Dwarf Elliptical galaxy?

----------------------------------

G1 is one of the brightest globular clusters belonging to M31, the Andromeda galaxy. At 13 .2 Mag it is visible in most amateur telescope. In large scopes at high power stars start to resolve. So what is G 1 ? There are lots of different ideas as to what it is. Here are a few things to think about when you are viewing this most interesting object. 1-- G 1 is three times larger than Omega Centauri our largest globular cluster. 2-- G 1 is about the same distance from the core of M31 as our Large Magellanic Cloud is from ours. 3-- The metallicity of the stars in G 1 is very near the metallicity of stars in the core of Dwarf Elliptical galaxies.

871

G 1 is the brightest cluster in M31 but according to S. G. Djorgovski of Caltech not the most massive cluster. I will list below three cluster that are near the mass of G 1 or larger. All should be within reach of most scopes.

G 78

RA
00 41 01
DEC
+41 13 47

Mag 14.2

872
----------

G 213

RA
00 43 14
DEC
+41 07 23

Mag 14.6

873
----------

G 280

RA
00 44 29
DEC
+41 21 37

Mag 14.2

874


In the image above 3.7 to the South West of G 280 is the cluster G 272 at 14.7 Mag it makes for a interesting field of of view to have two clusters in the same telescope view!!
----------

I hope you will try some of these "Super Size" clusters next time you are observing and as usual-----

“Give it a go and let us know!”

Good luck and great viewing!

[Howard B]

Hi Jimi,

It seems that UCD's are more common than the tiny "globulars" the Milky Way has, so maybe we should call our little star spheroids something like MGC's - mini globular clusters. Anyway, the latest observation I have of G1 is from 2006, and my notes read:

"Not much larger than the nearby field stars in this so-so seeing, G1 is still relatively easy to pick out because of the distinctive star field it's in. No stellar points, it just looks like an out of focus star. 812x" No SQM reading but my notes mention that there was some light smoke drifting through around the time this OSP observation was made.

875 876

My quick sketch shows the distinctive triangle G1 makes with two field stars, and even though there was no hint of resolution it seems that on a really steady night there might be a chance to see a sparkle or two. I've only gone after G2 as well as G1, but the other three objects you've listed look like they'll be fun to track down. Thanks!

[Clear Skies]

My first observation of this huge, but visually tiny fuzzball was on 1 October 2011, 12" SCT:

179x: The cluster is an east to west elongated streak, even in brightness, slightly clearer when using AV. Against the SSW edge of the cluster is a mag. 13 star, superimposed. To the NE is a mag. 12 star, slightly farther to the NNE are two mag. 13 stars aligned NNE to SSW.

254x: Using this magnification the cluster is a small, almost round patch, slightly elongated east to west, to the ESE of a mag. 13-14 star. Likely due to the presence of this star the cluster appeared to be more elongated at a lower magnification.

Five days ago I again observed it. A nice lead-in to pinpoint the position of the cluster are the two stars to its NNE, aligned NNE to SSW along with the star to its NE. Together with these stars the cluster forms a triangle pointing SSW, with the stars forming the base of the triangle.
Visually, the cluster no more than a somewhat fuzzy star.

877

[Ivan Maly]

Here my observations of the other four M31 globulars from the OP, made three years ago with my 7" Maksutov:

G213, G272 - both non-stellar with stellar core, good night on Spruce Knob summit: http://ivm-deep-sky.blogspot.com/2013/08/m31-from-spruce-knob.html
G78, G280 - both star-like, average night at Cherry Springs: http://ivm-deep-sky.blogspot.com/2013/08/m31-with-7-night-2.html

[MarcE]

Hi Jimi, dear all,
nice objects - i really like GC in nearby Galaxies.
I observed G1 two time over the last years with 15 inches (350x) and also 10 inches (220x). In both cases the GC was easy with direct vision. In both scopes G1 looked non-stellar and formed a nice triangle with the nearby stars.
I also observed G2 and G73 with my 15incher (350x). G2 was quite difficult compared to G1 (averted vision), but G273 was also possible with direct vision.
Btw: last week i observed GC C39 and C27 in M33 - much more difficult than the GC in M31 i observed before; but nevertheless much fun!
Clear skies
Marc

[MarcE]

Correction: G2 and G273 are located in Pisces - maybe not the right place to describe them here!
Sorry for that.
BR
Marc

[Paul Alsing]

It just so happens that on September 3rd I was in a group that used the 60" on Mt. Wilson for the entire night, and G1 was one of the objects viewed that night. The "Mickey Mouse" asterism was clearly apparent and the globular itself was obviously very different from the other 2 stars, what with being fuzzy and all... but overall it was a lousy night on Mt. Wilson, the sky was so bright from the LA lights that night that I was wishing I was in the desert with my 25" instead...

[reiner]

I observed G1 last week during a slightly overcast night, when fainter objects where out of question. It took some time to locate the asterism, as I did not have a precise finder chart. G1 was relatively bright and appeared fuzzy.

I need to make finder charts for the other three. These appear to be more interesting than most of the other (in my telescope only stellar) GCs of M31.

[Uwe Glahn]

With 16" and higher power I could also detect a fuzzy character of G1

16", 600x, Seeing II, Nelm 6m+
http://www.deepsky-visuell.de/Zeichnungen/MayallII.jpg

[RolandosCY]

And here is my rendition of G1 from a few days ago. I did observe it under relatively dark skies (SQM 21.55 with the device pointed in the direction of Andromeda) from a 1,700ft altitude site. The globular was pretty easy to locate, and have since showed it to other people under brighter skies, it seems to be quite easy in the 18". I did not achieve any resolution but the surface does appear to be granular. Perhaps under greater magnification a star or two could poke out. Definitely, the "Mickey Mouse head" effect is readily visible and becomes more pronounced if you de-focus slighly!

My plan is to try for G1 with my 6" f5.9 achro as soon as the moon gets out of the way, it seems to be within the capabilities of a 6" refractor...

929