Helix Galaxy (NGC 2685)

(From the 'Internet Encyclopedia of Science'.

An unusual lenticular galaxy in the constellation Ursa Major that is a member of the very rare class of polar ring galaxy; it is also known as the Pancake Galaxy. Several thin filamentary strands, consisting of knots of luminous star-forming regions and hydrogen gas, with a diameter comparable to the main disk, form a helical band perpendicular to the main disk and centered on the galactic nucleus. These structures suggest that NGC 2685 once had a companion, perhaps like one of the Milky Way's Magellanic Clouds, that was captured into a polar orbit and had its stars eventually merged with those of the larger system, leaving behind the companion's interstellar medium. New generations of stars formed from this material to produce the luminous ring seen today. It is possible that if the Magellanic Clouds had been closer to the Milky Way, they too would have created a polar ring around our galaxy. Perhaps a foreshadowing of this process can be found in the so-called Magellanic Stream, a string of hydrogen clouds trailing the Magellanic clouds and extending thousands of light-years along their orbit of the Milky Way.

I've been fascinated by the 'helix' for many years now and I think the above description explains precisely why. I have tried many times to image it but it is a truly difficult target and have had very limited success. I thought I would try it with my SX H9C camera, which might have more chance of success, having an image scale of 1 arcsec/pixel and a fov of 25' x 20', with my 10" f4.8 Newtonian. This image is as good as I have been able to get. It's not very good but, with a bit of imagination, you can just make out some of these rings that circle the galaxy - can't you??

Although the central parts of the galaxy are quite bright (12.5) the rings and the outer areas have extremely low surface brightness values (16.5 or less). It's overall size is 5' x 2.5'.

My image consists of 75 x 60 second exposures. The skies have been very poor over the South coast recently, with severe skyglow caused by hazy mist and fog; hopefully things will improve soon, because I want to get some decent exposures of this intriguing object. Because it's such an enigmatic subject with such interesting science, I thought it worth showing this image, despite the rather poor quality of signal.

Interestingly it is in Arp's catalogue, no. 336 and he classified it as 'unique'. I think he's right there!