Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939) (Niall MacNeill)

Celestial hemisphere: Southern · Constellation: Virgo (Vir) · Contains: HD113799 · NGC 4939

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Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939)

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Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939)

I have recently imaged two galaxies, NGC 6744 in Pavo and NGC 4939 in Virgo. Coincidentally they are both about the same size at 180-190 thousand light years across and 75% bigger than the Milky Way and are tilted towards us at about the same angle (~ 50 degrees). They are both spirals, although NGC 6744 has a small bar at its centre where NGC 4939 does not, however the latter, being a Seyfert Galaxy, has a small bright centre. Another difference is that there is quite a bit of Ha emission in NGC 6744 but little in NGC 4939.

However, the major difference between them is that NGC 6744 is 31 million light years away, where NGC 4939 is 120 million light years away, so nearly 4 times further. Of course this means its apparent diameter is 4X that of NGC 4939.

It struck me that seeing the two images side by side, from the same set up and therefore Field of View (FOV), would give a good sense of scale and depth. As simple as that. I hope that is as thought provoking for you as it was for me. Clearly, NGC 6744 being closer to the Milky Way has many more foreground stars.

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Status	Advanced success
Started	...
Astrometry.net job	8289533
PixInsight job	98CQY7K4DEM717A2OFMP35YI6M1QHGSY
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	13h05m40s.311
RA (top/left)	13h08m31s.840
RA (top/right)	13h02m50s.859
RA (bottom/right)	13h02m48s.126
RA (bottom/left)	13h08m29s.471

Dec (center)	-10°18′44″.79
Dec (top/left)	-09°58′48″.82
Dec (top/right)	-09°57′42″.39
Dec (bottom/right)	-10°38′35″.29
Dec (bottom/left)	-10°39′15″.91

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Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939)

Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939)

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Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939)

Comparing two galaxies of approximately the same size but widely differing distances (NGC 6744 and NGC 4939)

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