Two standout pairs of interacting spiral galaxies in Virgo, with striking and starkly different morphologies, are NGC 4567/4568, sometimes referred to as the "Butterfly Galaxies", and NGC 5426/5427, also known as Arp 271. After wanting to try my hand at these targets for a long time, I finally took a turn at both this spring as a small project, and am posting the two images one right after the other, which I hope will create an interesting juxtaposition. These are challenging objects, given the smaller angular scales on which the "action" is taking place in both, and there are relatively few images of either pair on Astrobin, especially Arp 271, of which there is only a relative handful.

I'm starting with the Butterfly here, while my image of Arp 271 is in my next post.

The Butterfly [†] comes before Arp 271 in Right Ascension, and is the nearest of the two pairs, at a distance of about 60 million light years, roughly half that to Arp 271. The apparent overlap between the two spirals in the Butterfly leaves little doubt that they are undergoing a collision, with the galaxy cores separated by only about 20,000 light-years. Despite their proximity to one another however, they are apparently still in the early stages of the collision, with millimetre-wave maps of molecular clouds providing clear evidence that a collision front has formed between the galaxies, but significant starburst activity in the overlapping region has yet to develop. 

I've oriented the shot in a way that I think accentuates the impression of a collision, with the larger spiral NGC 4568 on the right appearing to slice into the hapless smaller spiral NGC 4567 from above, like the blade of a power saw. Tidal forces have noticeably distorted the shape of the smaller galaxy, with a spiral arm on the left trailing behind the main disc, which is also significantly distended towards its lower left. I think there may be signs of increased star formation in the inner disc of the smaller spiral, where there are noticeably bluer sections and pockets, and there is also a suggestive blue region in an arm of the larger spiral that descends into the rear of the smaller galaxy. I cropped the full frame to try to heighten to the overall illusion of depth and motion, with the bright stars in the lower left corner setting the Butterfly into the background, and the greater concentration of background stars towards the upper left corner drawing the eye diagonally across the field, roughly in line with the plane of NGC 4568.

This image is the result of just under 6 hours of integration in luminance and 10 hours in RGB colour, acquired over the course of eight nights in April. With seeing conditions that were average on most of those nights, I felt that the image was not up to presentation at the native resolution of the telescope/camera combination, and have downsampled it by 75%, with a resulting plate scale of about 0.62"/pixel. The field-of-view of this crop is about 31'x26'.

[†] Another informal name for the Butterfly has been in wide use for many years, but NASA recently issued a statement citing this as one of two initial examples of astronomical objects with historical nicknames that it will no longer use, since these "may have historical or culture connotations that are objectionable or unwelcoming."