NGC3169LRGBrevFinalcropCDK1000_27Feb2023_1024[1].jpg
Unraveling NGC 3169
Image Credit & Copyright: Mike Selby & Mark Hanson
Wow, that's a great image!
Mark Hanson and Mike Selby are such great astrophotographers/astro image processors!
APOD Robot wrote:
Spiral galaxy NGC 3169 looks to be unraveling like a ball of cosmic yarn.
Yes, that's right, isn't it? Because it is NGC 3169 that is taking the brunt of the interaction between itself and its companion galaxy, NGC 3166.
Let's take a look at what's happening:
APOD 2 March 2023 NGC 3169 annotated.png
NGC 3169.
APOD 2 March 2023 NGC 3166 annotated.png
NGC 3166.
What can I say about NGC 3169? The inner part of it is well-ordered, with the thickest dust lane seen anywhere in these two galaxies, and a ring of pink nebulas. NGC 31689 may originally have been a galaxy with most of its star formation concentrated in a blue ring, like
NGC 1433 (except that NGC 1433 has most of its star concentrated in
a tiny nuclear ring, oh well).
Anyway, that is perhaps what NGC 3169 looked like from the beginning. But its interactions with NGC 3166 has led to it being contorted into stellar streams, bow shocks, tidal shells, disconnected young star clusters and discarded puffs of old stars. What a mess!
NGC 3166, a you can see, is much less affected by the interaction. But you can indeed see that NGC 3166 was in all probability a barred spiral galaxy before, and you can still se the remnants of an inner ring and a large bar structure with bar-end enhancements. Most like NGC 3166 has already lost all its "loose fluff" and now it is holding tight to its stellar possessions. There is not much gas left in NGC 3166, so the galaxy does not have to hold on to that.
There is a mess of tangled thin dust lanes in NGC 3166 that makes me think of NGC 1316. But NGC 1316 is a lot more disturbed than NGC 3166, which mostly keeps its act together.
For some reason the image on the right won't open, even though it is an APOD (from
May 17, 2022). But if you click on the little "failure to open" symbol, you can see the picture.
There is a very blue-looking dwarf galaxy next to NGC 3166, designated NGC 3165. I checked its color indices and found that it is actually not quite as blue as today's APOD suggests. Here is a more realistic picture of NGC 3165:
There is another galaxy near NGC 3166, but I have failed to identify it. It is a galaxy of old stars only, and interestingly, it has a nucleus. (Unless that is a foreground or a background star masquerading as a nucleus.) The galaxy itself is transparent and faint enough that it is not likely to be a background object, and it is small enough that it is not likely to be a foreground object. So it is a companion of NGC 3166. Or rather, it is a companion of the interacting pair of NGC 3166/NGC 3169.
Ann
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