Stephan's Quintet There are six galaxies plainly visible in this image (lots more smaller galaxies scattered in the image), ranging in brightness from the very faint NGC7318A (magnitude 13.1) to the extremely faint NGC7320C (magnitude 16.57); the five in the middle are commonly known as Stephan's Quintet. Four of those galaxies show essentially the same redshift, suggesting that they are at the same distance from us, approximately 290 million light years. At that distance, the three closely-knit galaxies at the center have a combined width of about 400,000 light years (including the tidal tail on NGC 7319). The larger bluish spiral above the center of the group, NGC7320, has a much smaller redshift than the others, suggesting that it is much closer to us than the others, probably a foreground object which happens to lie along the line of sight to the more distant galaxies, about 35 million light years away from us. Of the four distant galaxies in the group, three seem to be colliding, showing serious distortions due to gravitational tidal forces. The fourth, NGC7317, to the left of the others, is a normal appearing elliptical galaxy. Another collision that wreaked havoc was triggered by a galaxy that is no longer part of the group. NGC 7320C, to the right of the others, plowed through the quintet several hundred million years ago, pulling out the 100,000 light-year-long tidal tail of gaseous debris from NGC 7319 and adding gaseous fuel to the northern starburst region. NGC 7320C is now 460,000 light-years away from the rest of the carnage. The clusters in NGC 7319's streaming tail are 10 million to 500 million years old and may have formed at the time of the collision.

The gravitational interactions among the galaxies cause them to become misshapen, and cause the "tidal tails"--the extended bright "arms." It is thought that the five members of Stephan's Quintet eventually will merge into one galaxy, after a some hundreds of millions of years of dancing; NGC 7318A and NGC 7318B are well along in the process of merging, but it will take much more time for NGC 7320C to be reeled back in to the others. .

This was one of the first group of images released by the James Webb Spact Telescope; to see its effort, click here.

A small version of the above photo is included below, showing the names of the galaxies.

I last imaged this 19 years earlier, with a smaller scope, from my suburban yard. To see that effor, click here.

 

Technical Information:

L:R:G:B: 850:180:180:260 (a total of over 24 hours of light-frame exposure time); luminance was a blend of 30-minute images and 5-minute images; red and green exposures were all 15-minute exposures; blue all 20-minute exposures. The luminance layer consisted of 24 thirty-minute images through the luminance filter and 26 five-minute images. The red channel is a combination of twelve 15-minute images thorugh a red filter. The green channel is a combination of twelve 15-minute images through the green filter. The blue channel is a combination of thirteen 20-minute images through a blue filter.

Equipment: RC Optical Systems 14.5 inch Ritchey-Chretien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 camera with internal filter wheel (SBIG filter set), guided by an SBIG AO-X, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSkyX.

Processing: All images calibrated (darks, bias and sky flats), aligned, combined and cropped in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization, color calibration, NoiseXTerminator and BlurXTerminator) done in Pixinsight; some cleanup finish work was done in Photoshop CC.

Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken on many nights in July and August of 2022. Image posted October 9, 2022.

Date: Image scale of full-resolution image: 0.56 arcseconds per pixel.

Seeing: Generally good; luminance images varied in FWHM from 1.6 to 2.3 arcseconds.

CCD Chip temperature: -25C

Copyright 2022 Mark de Regt

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