April 20, 2013

NGC 4631, the Whale Galaxy and the Remora (March & April, 2013)

This asymmetrical galaxy is 13-25 million light years away in the constellation Canes Venatici (the Hunting Dogs).  The shape reminds some of a whale.  I'd say it's a baleen whale, almost certainly a gray, especially given the mottled appearance.

The galaxy immediately above the Whale is NGC 4627.  Probably the two are interacting gravitationally, and this may explain the asymmetrical appearance of each.  Together they are cataloged as #281 in Halton Arp's Atlas of Peculiar Galaxies.  I'd say if NGC 4631 is the Whale Galaxy then NGC 4627 is the Remora.

The image itself has a peculiar shape.  I took two sets of sub-frames, one in March and one in April.  The camera was placed at a slightly different angle with respect to the telescope in March than in April.  So I had edge lines in the final image.  Normally, I would crop all those out, but I wanted to show all of the little galaxies floating about in this part of the sky, especially the irregular galaxies, so I selected around all of them, then added a darker layer outside of the selection.  Exploring in this image is pretty fun.  You might compare the full resolution image to what is shown for this area in sky-map.org, linked at right. The dimmest stars in this image are magnitude +18.5.

Telescope: Astro-Tech AT111EDT and William Optics AFR-IV (eff. at f/5.6)
Camera and Exposure: SXVF-H9 (104x480" (13.86 hours)), Alnitak Flat-man flats
Filter: Astronomik CLS
Guiding: SX Lodestar and SX OAG
Mount: Takahashi NJP
Software: Nebulosity, Maxim DL, Photoshop CS3
Location: The Woodlands, TX

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