I seem to get a big charge out of getting photos with multiple deep-sky objects in them, so what better target than the Virgo Cluster of Galaxies? It’s an area of the sky just East of Leo (in Virgo actually!) that is the location of the nearest ‘super cluster’ of galaxies. If you hold up your hand at arm’s length, fingers spread in this direction of the sky you will have over 2000 galaxies behind your hand.
I took this image in the early part of the year and have been working on it in Photoshop for a few months now manually cleaning the camera noise out of the image so you can see the faintest, most distant galaxies against a nice black sky background. Well I finally finished and here it is:
Markarian’s Chain in the Virgo Cluster of Galaxies. I have Identified over 200 galaxies here. Click for a bigger version.
Heart of the Virgo Cluster
I had shot this area of the sky before but with a telescope that sees a lot less sky but I wanted to see how many cluster members I could get and it would also serve as some kind of a benchmark as to “how deep can you go”.
The image to the right was promising: it had pretty good detail in the edge-on spiral galaxies that flank the two big elliptical galaxies M84 and M86 and just peeking through the noise there were some background galaxies–I think I counted 17 or so at one point.
Distant galaxies look like little fuzzballs on an image and even though they are really big they are also very far away so they appear as little smudges, barely discernible as “non-stellar” blobs lurking above the noise-floor of the image.
The hardest thing about processing these images is finding the right settings and procedures to get the part of the image you want to be easily visible and the camera noise down so it isn’t visually distracting.
Well that turned out to be impossible with this image–the faint stuff was so diim that if you wanted to see it at all you had to stretch and amplify the light curve so much that the noise came right up with it as a speckling of tiny variously colored squares. I tried a number of automated techniques to get rid of these things and everything I tried was also damaging the parts of the image I wanted to keep.
So I took a deep breath and resigned myself to the fact that I would need to clean this image manually by selecting an area of the screen, then deselect the parts of the image I wanted to keep, then replace everything else with a nice sky background color. I did this about 300 times over four months to get through the entire image.
Closeup of M88 from the upper right of my image. The only galaxy with any real detail here, it’s one of the closest at 36 million l.y.
So what do you do with an image like this? On one hand it’s amazing that I, as a hobbyist can take pictures of something that is 50 million light-years away! On the other hand, it’s just a bunch of fuzzy blobs in a nice star field. The only galaxy in here that shows any structure at all is M88 at the top right and there really isn’t any visual ‘wow factor’ on par with a great shot of some pinkish cloudy nebula with it’s exquisite detail.
I really wanted to know “ok, what exactly do you have here” in this image so I decided that I would compare my image to a map of that part of the sky from my astronomy program, “Sky Safari Pro”. So I got the approximate area of the sky up on the map on one screen and zoomed way in on my image to start seeing what I could find on my map and was it visible in my image. Every time I found one I put it into a spreadsheet I started with the galaxy name, distance (if known) and a note if there anything notable.
I had been telling people at my stargazes that I thought there were maybe 35 or so galaxies in the image, based on me just poking around there. Well as I started cataloging I realized I was waaaaay wrong about that; it’s more like 200!
Map of the Virgo Cluster from Sky Safari. This is the approximate area of my photo
Once I got into it and had finished all the bright easy ones (about 20 or so) I dove in deep and started trying to identify the smallest little smudges on my image and seeing if they showed up on the map. Or sometimes I would look at the map and see if there was a wisp of light where there was supposed to be something. It was like the Russian dolls of galaxy hunting, the harder I looked, the more I would find. Here’s the area around M86, the largest of the two elliptical galaxies at the center of the image, both map and photo, side by side.
M86: Map and close-up of my image. How many galaxies from the map can you find one the image?
So the big galaxy, M86 is 57 million light years away, putting it squarely in the center of the Virgo Cluster whose members range from the relatively near 30 million l.y. to roughly 70 million l.y. on the far edge of the cluster. Well I was astonished to find out that galaxy PGC 169281, visible in the halo of M86 was 1 billion, 700 million light years distant! just barely above the noise floor of my image. Well this was now getting really exciting and for a week I sat there comparing map to image and cataloguing what I could find on the spreadsheet.
Since my noise cleaning activities took place over such a long period of time and my methods got more refined I realized a probably ‘cleaned’ a number of galaxies out of the image in the upper right (where I started the process) before I had become aware of just how faint some of this stuff is. I gradually became aware of what a slightly blurry star looked like compared to a distant galaxy. This process was also hampered by the fact that the image and the map were in slightly different orientations. This was no big deal when you had super easy to identify landmarks in the image but when I got out to the edges it got really difficult to make absolutely sure I could reconcile the image against the map. Sometimes I’d sit there for half and hour trying to get my bearings before I could be sure of what I was seeing.
So who was the distance winner in the image? Well that would be PGC 40480 which is 6 billion, 400 million light years away and is receding from us at 37.8% of the speed of light due to the expansion of the universe! Well this blew me away to find that one. That would mean that the light from that galaxy had been traveling in space for about half the age of the Universe. Or put another way, the image that I got (as diffuse and smudgy as it is) is of the galaxy as it looked 6.4 billion years ago, before the Solar System and Earth existed by 2 billion years, when the Universe was about half it’s current age!
So the real fun in this image is not the image itself it turns out, but what it represents and some good geek factor that just an average guy with above average motivation could even detect something like that.
Bill the Sky Guy
July 27th, 2019
Here’s the list of everything I could find and positively identify. I finally just had to stop and I estimate there are probably 25 more little smudgies that I didn’t get to or couldn’t reconcile against the map.
In just visually surveying the distances listed here, it really seems like there are three distinct galaxy clusters in depth in my image.
First the Virgo Cluster itself, 30-70 million light years, then there’s a second group from 300 to 800 million l.y. Out at 1 billion to 2.7 billion l.y. there is a 3rd cluster. I don’t seem to be easily able to track down the names of these clusters or perhaps they’re all considered part of some larger supercluster–this is probably above my amateur astronomer pay grade. Suffice it to say that it really brought nome to me the three-dimensionality of the Universe and kind of gave me a window to the thrill the earliest researchers must have had when they started getting these images for the first time, which wasn’t all that long ago, and during my lifetime!
