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Interesting galaxies thread


Martin Meredith
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I also looked at this one a while back. It isn't as clear as in mono but NGC 4302 does show some interesting reddening in the central region. Thanks for the link Bill -- I'll check to see if any of this colour is meaningful!

687415019_NGC430205Apr22_13_26_03.png.1aa80f84c9215ffc8d4715fc879f95c0.png

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Here are few more galaxies of interest, simply because they are in the IC catalogue and are around the 1 billion distance and all visible with a large Dob. 2881 and 3848 are both galaxy pairs and 2860 fov has PCG galaxies in view which are 2 billion lyrs or more. The quasar just below it lurks around the 8 billion lyr distance.

Mike

757368354_IC288103Apr22_08_19_31.png.03f5249ee6b0ab78c0879a5d73200698.png1491976020_IC384803Apr22_07_53_32.png.61ade9e992611d3fa56869215f02fdc0.png

47629454_IC286003Apr22_08_21_24.png.d074ffe150d2306e63e356d7251a1744.png

Edited by Mike JW
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  • 2 weeks later...
Posted (edited)

Going back through some recent captures I came across M77 in Cetus.

This is how it looks on the 'normal' settings I use for LRGB captures (gamma stretch), showing an extremely bright core region within which it is hard to discern any structure (even on a single blue sub it is bright and stellar). The spiral arms show what appear to be star-forming region (blue), all bathed in the yellow glow of a halo? of stars

image.png.cccf34705e7e7108a038875c0cbc0404.png

But it turns out that the galaxy is much more extended than this. Switching to hyper stretch and applying some sharpening produces a result that is not 'pretty' but which reveals a clear outer structure with what look to be a pair of additional spiral arms but which could well be continuations of the ones visible in the above shot. 

image.png.aaf44f0634031085ee0b4894e101f367.png

Something I've started to explore is subtracting the responses of different filters. This is early days but here's an example of using the difference between the red and blue filter as the luminance component. There is no finesse to this at present, hence the horrible artefact on the bright star to the left, but the process does hint at a double structure of some kind at the core (again, this might be an artefact).

image.png.e41c5182db17fed94ad3b70dec17d1f5.png

Edited by Martin Meredith
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It would be remis not to include M87 on this thread.

Whilst the capture is not much to look at, the satisfaction of being able to observe this behemoth of a galaxy with its relativistic jet of synchrotron radiation blasting out (at about 2 o'clock) from the super-massive blackhole at the galaxies core - and all with a modest telescope and camera in just a few seconds.

What's not to love!

Pat

M87_2022.4.2_22_06_04.png.b29d480cb0dbe5ddf506ae404fa78d1f.png

M87_2022.4.2_22_09_40.png.019d150e3e9ec7ef6538ebb982221230.png

 

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I too couldn't let a clear night pass without snapping a shot of the M87 jet...When I first saw posts (probably 12 months ago) showing this I was amazed at how easy it was to capture...It was plainly visible in a single 10 second exposure. Apparently there's also a jet in the opposite direction, but this is more difficult to capture. I let my capture run for 5 minutes in the vain hope of being able to get a glimpse of it, but I guess it's not going to happen. Maybe next time 😉 .

image.png.e593cd0331778a96b3920f442b8d54f9.png

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  • 3 weeks later...
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Here's a quick snap of a pair of mag 7-ish yellow-orange stars (both have B-V colour indices of ~ 0.9) in Bootes, close to the border with Corona Borealis. Gliese 593 is also known as Otto Struve 298, a very close double (sep 1.2"). 

image.png.2707400668eea229f9fe9901b57ce169.png

However, since this is the interesting galaxies thread, using a more aggressive stretch reveals the main point of the operation, a pair of NGC/IC galaxies, plus a third galaxy, the triplet curving gently through the stellar pair. 

image.png.b7c485f7164c393529cb4a86a38a5f7d.png

 

Distance-wise, the stellar pair are both listed at 73 light years (so presumably not just an optical pairing), while IC 4563 and NGC 5966 are about 30000 times further out at around 215 million light years. The middle galaxy, mag 16.4, is nearly a billion light years away.

 

Martin

Edited by Martin Meredith
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For a moment  Martin, I thought you had lost the plot (although as you know I do like doubles)!!!! and then all was revealed - a delightful capture - excellent to have hunted this one out.

Mike

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Well, it wouldn't be the first time I've lost the plot... Anyway, last night with it being clear but accompanied by a bright moon overhead, and there being few open clusters on offer towards the south, I did check out some doubles (may post elsewhere) purely for their aesthetic value. 

But with Virgo so well-placed the call of the galaxies was too strong to ignore, and the highlight of the night for me in spite of the moon was NGC 4762 in Virgo. This is a member of VV 1573 but the way my ASI 290 sensor was oriented was such that the pair only just squeezed on to the sensor, so I focused more on NGC 4762.

This is a perfectly edge-on galaxy and as such shows a clear core.

Below is what I tend to think of as a  'colourised' capture: that is, I started off in luminance-only, then added some RGB at the end to capture the pale peachy glow of the "arms" and the brighter yellow core.

image.jpeg.2f3ec171d9f44e9cac19e5908d1150ef.jpeg

Just as with my previous post, no one stretch shows it all, and there is much more to this galaxy than its clean-cut central region. Barely visible in the gamma-stretched image are very faint curved extensions to the central streak of light. These are better seen using a hyper stretch on a negative image:

image.jpeg.78b80c6020abe14546b1f599c1e43dce.jpeg

The reason I put "arms" in quotes above is that this version makes me wonder if what we're seeing in the gamma-stretched image is the core plus an extensive bar, with the spiral arms only showing up in the stretched form. At any rate, there is a clear asymmetry in the outer parts and what to me is a surprisingly abrupt cutoff between the linear bar(?) and the rest. Time for some reading I think...

Martin

 

 

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One classification describes NGC 4762 as SB(r)0^0^ sp LINER - Ok it has a bar, is likely to be a spiral but how do they get to work out that it has an inner ring and what does the  0^0^ mean??

 

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The de Vaucouleurs Atlas describes it as "one of the most remarkable S0 galaxies in the sky" with a "very well defined inner disk zone flanked by a noticeably warped thicker disk". They cite a 1984 article by Wakamatsu & Hamabe that suggests that "the innermost hump represents the ends of a bar oriented at an intermediate angle to the line of sight" and that the very sharp edge that we see is an edge on view of a lens.

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