Celestial hemisphere:  Northern  ·  Constellation: Pisces (Psc)
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Arp 11, Gary Imm
Arp 11, Gary Imm

Arp 11

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Arp 11, Gary Imm
Arp 11, Gary Imm

Arp 11

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Description

This Astrobin Debut Object is a grouping of 4 main galaxies, along with many smaller ones, located in the constellation of Pisces at a declination of +14 degrees.  In his Arp catalog, Dr. Arp classified this object into the category of Spiral Galaxy with Split Arm. 

This is an interesting group of galaxies.  The 2 larger ones, UGC 717 and UGC 719, both have double rings – a mid-region ring around the bar, and a pseudo-ring circumventing the outer disk.  The magnitude 14 galaxy UGC 717 is huge at 200,000 light years in diameter, dwarfing the Milky Way sized UGC 719.

What is causing the disturbance in UGC 717, which is 440 million light years away?  It is not UGC 719, which is 540 million light years away.  It is not the closest spiral to it, LEDA 4123, which is 800 million light years away.  Two small galaxies appear just above UGC 717 and could be the disturbance cause.  But these two have no distance information and look like distant galaxies to me.   

The outer disk structure of UGC 717 is messy on both sides from the disturbance.  It is possible that the disturbance culprit has already been absorbed into the large galaxy’s disk.  This would also explain why this galaxy is huge. 

Note that the core, bar, and inner regions of UGC 717 and UGC 719 are almost identical in size and shape.

Many other interesting smaller galaxies lie scattered throughout the background, stealing our attention from the larger galaxies.

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