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Extragalactic Globular Clusters, 



    
        

            Gary Imm

Extragalactic Globular Clusters

Getting plate-solving status, please wait...
Extragalactic Globular Clusters, 



    
        

            Gary Imm

Extragalactic Globular Clusters

Acquisition details

Basic astrometry details

Astrometry.net job: 5387112

Resolution: 6000x4000

File size: 11.3 MB

Locations: Backyard (Mag 20.8 - Bortle 4.5), Onalaska, Texas, United States

Data source: Backyard

Description

The Milky Way has over 150 globular clusters, including outstanding ones such as M13 and Omega Centauri.  These are fantastic showcase objects which can consist of millions of beautiful colorful and bright stars.  My Astrobin globular cluster collection shows 70 of these 150 clusters.  Typical large Milky Way clusters are about 20,000 light years away, 150 light years in diameter and 20 arc-minutes wide in our apparent view. 

Although Milky Way globular clusters can provide a lifetime of interesting imaging, it is possible to image globular clusters in other galaxies beyond our Milky Way.  They will never be spectacular objects because of their vast distances, but I find it fun to peak in on these tiny extragalactic treasures that few people have seen.      

I have limited the galaxies selected here to a distance of 3 million light years or less.  At that distance, the largest globular clusters will appear as a 15 arc-second diameter object in our apparent view.  This is just large enough for the cluster to appear as a fuzzy ball and make it distinct from the look of a star.   It is possible to image globular clusters in galaxies much further away, up to 50 million light years.  But their appearance is very faint and not terribly rewarding.

 As you might expect, the clusters on this poster are small and are only seen to be distinct from stars in the full resolution view or the zoomed-in view.  Even at that, they sometimes look stellar in appearance.

The galaxies considered here exclude those in the far southern sky which I cannot reach, specifically the SMC and LMC.  Also, I have excluded objects from the Sagittarius Dwarf Spheroidal Galaxy, which I covered in a separate posted image.  These objects were born as extragalactic objects but since have been absorbed into our Milky Way.

Note that these are not the “brightest 50 extragalactic clusters”, just 50 of the brightest.  I wanted to image clusters in a number of different galaxies – M31 tends to have most of the bright ones.  

There is no standard naming convention for extragalactic clusters as far I can tell.  Each galaxy tends to have its own convention, initiated by the scientist who discovered them.   I obtained this cluster list from various published papers and magazine articles.

A special note here about cluster G1, at the bottom right of the image.  It is the brightest of 500+ globular clusters that have been identified so far as belonging to the Andromeda Galaxy (M31), but is located far away from the core.  It is about 2.5 degrees southwest of the core, which corresponds to a distance of about 120,000 light years.   G1 is believed to have twice the mass of Omega Centauri.

If you would like to read more about any of these galaxies, each of them has previously been uploaded and described individually on Astrobin. They, and this poster, all reside in my Astrobin Extragalactic Globular Cluster Collection.

If you would like to access all my DSO compilation posters, please click here.

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Histogram

Extragalactic Globular Clusters, 



    
        

            Gary Imm

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