APOD: Unraveling NGC 3169 (2023 Mar 02)

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APOD Robot
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APOD: Unraveling NGC 3169 (2023 Mar 02)

Post by APOD Robot » Thu Mar 02, 2023 5:05 am

Image Unraveling NGC 3169

Explanation: Spiral galaxy NGC 3169 looks to be unraveling like a ball of cosmic yarn. It lies some 70 million light-years away, south of bright star Regulus toward the faint constellation Sextans. Wound up spiral arms are pulled out into sweeping tidal tails as NGC 3169 (left) and neighboring NGC 3166 interact gravitationally. Eventually the galaxies will merge into one, a common fate even for bright galaxies in the local universe. Drawn out stellar arcs and plumes are clear indications of the ongoing gravitational interactions across the deep and colorful galaxy group photo. The telescopic frame spans about 20 arc minutes or about 400,000 light-years at the group's estimated distance, and includes smaller, bluish NGC 3165 at the right. NGC 3169 is also known to shine across the spectrum from radio to X-rays, harboring an active galactic nucleus that is the site of a supermassive black hole.

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Ann
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Re: APOD: Unraveling NGC 3169 (2023 Mar 02)

Post by Ann » Thu Mar 02, 2023 8:23 am

NGC3169LRGBrevFinalcropCDK1000_27Feb2023_1024[1].jpg
Unraveling NGC 3169
Image Credit & Copyright: Mike Selby & Mark Hanson


Wow, that's a great image! :D 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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Re: APOD: Unraveling NGC 3169 (2023 Mar 02)

Post by David G » Thu Mar 02, 2023 12:32 pm

Why is NGC3169 unravelling, when there's a supermassive black hole at its centre? Shouldn't that black hole be sucking NGC3166 into it? Or is there an even bigger black hole in NGC3166?

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Chris Peterson
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Re: APOD: Unraveling NGC 3169 (2023 Mar 02)

Post by Chris Peterson » Thu Mar 02, 2023 1:50 pm

David G wrote: Thu Mar 02, 2023 12:32 pm Why is NGC3169 unravelling, when there's a supermassive black hole at its centre? Shouldn't that black hole be sucking NGC3166 into it? Or is there an even bigger black hole in NGC3166?
Black holes don't suck things into them, except for dust and gas that is orbiting very, very close such that their densities become high enough that they are fluid, and lose energy to collisions and friction. Otherwise, a black hole is just the same as any other mass... lower mass stuff orbits it. A supermassive black hole's impact on a galaxy is subtle. It doesn't hold things together, as it represents only a tiny fraction of the total mass.
Chris

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johnnydeep
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Re: APOD: Unraveling NGC 3169 (2023 Mar 02)

Post by johnnydeep » Thu Mar 02, 2023 7:16 pm

As for that faint spherical cloud to the lower left of NGC 3196, it's apparently indeed the known dwarf galaxy PGC 29873:


The image is from this page: http://www.jthommes.com/Astro/NGC3166.htm
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Re: APOD: Unraveling NGC 3169 (2023 Mar 02)

Post by VictorBorun » Wed Mar 08, 2023 1:22 am

Chris Peterson wrote: Thu Mar 02, 2023 1:50 pm
David G wrote: Thu Mar 02, 2023 12:32 pm Why is NGC3169 unravelling, when there's a supermassive black hole at its centre? Shouldn't that black hole be sucking NGC3166 into it? Or is there an even bigger black hole in NGC3166?
Black holes don't suck things into them, except for dust and gas that is orbiting very, very close such that their densities become high enough that they are fluid, and lose energy to collisions and friction. Otherwise, a black hole is just the same as any other mass... lower mass stuff orbits it. A supermassive black hole's impact on a galaxy is subtle. It doesn't hold things together, as it represents only a tiny fraction of the total mass.
I thought a supermassive black hole at a galaxy's centre can if anything blow its host stripping it of gas in a million years and making it an elliptic galaxy in a billion years.
I mean if that supermassive black hole get to eat another supermassive black hole or a globular stellar cluster, emitting a good portion of mc² in the form of gas shock waves