10 January 2017 | Draconian Galaxies

Draconian Galaxies

Credit & copyright: Markus Blauensteiner | Click image to enlarge

Image Data
  • Location: Austria
  • Camera: Sbig ST2000XM for Lumiance; SXVH-9 for RGB
  • Optics: 10“ f/4 Lacerta Newtonian for Luminance; 5“ f/5 Newtonian for RGB. L and RGB taken simultaneously
  • Mount: ASA DDM 60pro
  • Filters: Baader
  • Exposure: Luminance 35×15 min, RGB 13×15 min each; total 18.5 h

NGC 5963 (bottom) and NGC 5965 (top) are two spiral galaxies in the northern constellation of Draco, which are far apart and unrelated, and are just by chance appearing close on the sky.

NGC 5963, nearly face-on, is just about 50,000 light-years across and a mere 40 million light-years away from Earth. This galaxy is receding from us at approximately 655 kilometers per second. It has a rather bright center with several dust lanes in it. Its extraordinarily faint blue spiral arms which extend some distance out from the bright core, mark it as a low surface brightness galaxy.

But, although the stars of its spiral arms are not so bright, the arms are blue and must be dominated by young blue and relatively bright stars. And there probably is a good deal of star formation going on inside them. The reason why the arms are still so faint is that there just aren’t very many stars in them (yet), and certainly not very many intermediate or old stars.

NGC 5965, nearly edge-on to our line of sight, is over 200,000 light-years across and about 150 million light-years away from Earth, while it is receding from us at roughly 3,400 kilometers per second. This galaxy is well-formed and has an extensive bulge. It has a very obvious dust lane and probably several sets of dust rings in its disk.

It also seems to have a thick tidal tail of stars coming out of its disk (on our right hand side), although there is no sign of an interacting galaxy. Or could it be a small galaxy that is just being swallowed by the giant galaxy?

In the lower left part also visible are galaxies NGC 5969 and NGC 5971. The bright stars in the foreground are stars in our own Milky Way Galaxy.

Source

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