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Here's a first: ngc 4041 with extended disk


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There aren't many images online of this small gem in Ursa Major, and even fewer show the extended disk of this spiral galaxy. What's more, the extended disk shows a claw like arm, so maybe this galaxy should be called the Crab galaxy.

ngc 4041, the centrepiece of this image, is a spiral Seyffert type galaxy in the Great Dipper, about 70 Mly distant. It is a very active galaxy, with many HI regions where new star formation occurs. What is somewhat unusual is that these regions are scattered over the entire galaxy, including the nucleus. Hence the pink colour near the galactic centre.

What is even more unusual is the very weak extended disk, which has an arm that appears to line up with one of the galaxy's arms. This faint structure is, as far as I could find, only described in one scientific article. In this article it is speculated that the "three pronged" extension could be due to a past interaction with another galaxy.

Also in this image are several other galaxies, at approximately the same distance as ngc 4041. The larger of these, at the bottom of the image, is lenticular galaxy ngc 4036. This galaxy is in many ways the opposite of ngc 4041, in that it has no active star formation and is slowly losing its spiral structure. The remnants of a spiral are visible as weak disturbances in the disk.


Here's a close up of ngc 4041 and ngc 4036


Technical details:

Telescope/camera: SW MN190 and zWO ASI294MM

7 hrs RGB, 5.5 hrs L, and 2 hrs H-alpha

Processed in PixInsight

Edited by wimvb
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Great image of these rarities, and interesting write-up. You forgot to mention that you also caught some IFN down to the right😉

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Thanks, Göran. Yes, there is some ifn in the lower right corner, but generally it seems very weak in this region of the sky.

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