APOD: NGC 5101 and Friends (2014 Feb 08)

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APOD: NGC 5101 and Friends (2014 Feb 08)

Post by APOD Robot » Sat Feb 08, 2014 5:09 am

Image NGC 5101 and Friends

Explanation: This sharp telescopic field of view holds two bright galaxies. Barred spiral NGC 5101 (top right) and nearly edge-on system NGC 5078 are separated on the sky by about 0.5 degrees or about the apparent width of a full moon. Found within the boundaries of the serpentine constellation Hydra, both are estimated to be around 90 million light-years away and similar in size to our own large Milky Way galaxy. In fact, if they both lie at the same distance their projected separation would be only 800,000 light-years or so. That's easily less than half the distance between the Milky Way and the Andromeda Galaxy. NGC 5078 is interacting with a smaller companion galaxy, cataloged as IC 879, seen just below and left of the larger galaxy's bright core. Even more distant background galaxies are scattered around the colorful field. Some are even visible right through the face-on disk of NGC 5101. But the prominent spiky stars are in the foreground, well within our own Milky Way.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by Ann » Sat Feb 08, 2014 7:01 am

Oh, that's so interesting! What a lovely APOD!

NGC 5101 and NGC 5078 are similar in some respects - their sizes and their B-V indexes - but they are also really quite different. NGC 5101 looks a bit similar to NGC 1398, here portrayed by Adam Block. Both NGC 5101 and NGC 1398 have bright inner lenses, bars with bar-end enhancements, and rings surrounding their bars. The galaxies also have rather faint spiral arms. Even though NGC 1398 appears to have a little more star formation than NGC 5101, the different populations of NGC 5101 are beautifully apparent by their colors in today's APOD. The population inside the inner ring is really quite reddish and obviously very old, and some of the reddishness extends beyond the inner ring. But there is also an outer feature which looks like an outer ring (even though NGC 5101 clearly has spiral arms), and this outer feature is grayish-blue. This feature clearly contains young stars, but there are probably also stars of intermediate age and also perhaps old metal-poor stars.

The regular and beautiful shape of NGC 5101 is striking, and its beauty is enhanced by our nearly face-on view.

NGC 5078, by contrast, is seen almost perfectly edge-on. We can see its very thick central dust lane, whose "thick part" appears quite straight and undisturbed, while its "thinner parts" are stretched out, flared out and apparently elongated.

Personally I can see no obvious signs of star formation in NGC 5078, but its color indexes are very interesting and suggestive. Its B-V index is 1.040, which is really quite red, but its U-B index is 0.360, which is surprisingly blue in view of the galaxy's very red B-V index. I have to wonder if the U-B index of NGC 5078 has been "contaminated" by the obviously ultraviolet-bright dwarf galaxy IC 874, with which it is interacting.

The far infrared index of NGC 5078 is 10.384, which makes it almost two magnitudes brighter in far infrared than in blue light. This is often a signature of star formation, but I am uncertain if this is the case in NGC 5078's case. Clearly NGC 5078 is very dusty, but I still wonder if its U-B index is "its own" or partly its neighbour's. If the U-B index has in fact nothing to do with the small neighbour, then NGC 5078 must indeed have a respectable amount of star formation.

The color indexes of 5101 are quite different from those of NGC 5078. The B-V index of NGC 5101 is 1.005, similar to NGC 5078, but the U-B index of NGC 5101 is 0.565, considerably redder than NGC 5078's value of 0.360. Even so we can actually see young blue clusters in NGC 5101, while no young stars are apparent in NGC 5078.

What about the far infrared magnitude of NGC 5101? Its far infrared magnitude is 12.803, more than a magnitude fainter than its B magnitude. NGC 5101 is dust-poor.

What a fascinating APOD this is! It is so beautiful and detailed, and its colors are so well-balanced that they in themselves give us many clues to the nature of these beautiful galaxies.

Ann
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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by tomatoherd » Sat Feb 08, 2014 2:40 pm

As noted, there are distant galaxies visible through NGC 5101. The one at about 7 o'clock appears face-on, and very similar to NGC 5101 itself. It even seems to have darker, more rarified streaks within it. So what I find interesting is that if we are looking through this distant one, we are peering through THREE layers of galaxies: our own, NGC 5101, and the distant one.
Does anyone know of an example of FOUR layers???

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MargaritaMc » Sat Feb 08, 2014 4:56 pm

Many thanks for the first link in the text, to an annotated image. I find it helpful to know what the other objects are that are in the field of view.
M
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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by BillBixby » Sat Feb 08, 2014 8:35 pm

Most times I look at the APOD photo and just appreciate its beauty. Sometimes, as I read the description the need so save the picture to my APOD collection becomes apparent. Reading the discussions may have the same affect. Today's picture is so striking that my first reaction was to save it to my pictures and then read about it.

A truly beautiful picture. Thank you for the posting. And thank you for the discussion, however short it is so far.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by BDanielMayfield » Sat Feb 08, 2014 8:39 pm

Ann wrote:Both NGC 5101 and NGC 1398 have bright inner lenses, bars with bar-end enhancements, and rings surrounding their bars.
What causes bars and bar-end enhancements in many spiral galaxies?

Bruce
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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by geckzilla » Sat Feb 08, 2014 8:45 pm

Last I read, galaxy evolution and the presence of bars specifically is still fairly mysterious.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MargaritaMc » Sat Feb 08, 2014 9:35 pm

BDanielMayfield wrote: What causes bars and bar-end enhancements in many spiral galaxies?

Bruce
I've found the notes for the astronomy course presented by Chris Mihos of Case Western Reserve University in 2011 to be useful.
http://burro.astr.cwru.edu/Academics/Astr222/

On this page he writes specifically about barred galaxies.

Margarita
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by Anthony Barreiro » Sun Feb 09, 2014 12:04 am

I'm imagining incarnations of Charles Messier and Edwin Hubble on a small rocky planet orbiting a middle-aged dwarf star in the galaxy we call NGC 5101, pointing their telescopes at that big, bright nebula ... .
May all beings be happy, peaceful, and free.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by BDanielMayfield » Sun Feb 09, 2014 12:05 am

MargaritaMc wrote:
BDanielMayfield wrote: What causes bars and bar-end enhancements in many spiral galaxies?

Bruce
I've found the notes for the astronomy course presented by Chris Mihos of Case Western Reserve University in 2011 to be useful.
http://burro.astr.cwru.edu/Academics/Astr222/

On this page he writes specifically about barred galaxies.

Margarita
Thanks so much Margarita. Geckzilla, check out her second link. It was quite understandable.

Bruce
Just as zero is not equal to infinity, everything coming from nothing is illogical.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by geckzilla » Sun Feb 09, 2014 12:51 am

What I got from that is that somehow dark matter facilitates bar formation or bar stability. I'm not even going to pretend that I understand why a dark halo does this. :)
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MarkBour » Sun Feb 09, 2014 2:02 am

tomatoherd wrote:As noted, there are distant galaxies visible through NGC 5101. The one at about 7 o'clock appears face-on, and very similar to NGC 5101 itself. It even seems to have darker, more rarified streaks within it. So what I find interesting is that if we are looking through this distant one, we are peering through THREE layers of galaxies: our own, NGC 5101, and the distant one.
Does anyone know of an example of FOUR layers???
Interesting observation. I certainly don't know of an answer to your question. Assuming you will always count our own galaxy, regardless of the direction you look, I suppose your best bet of finding such a thing would be to look through either the Canis Major Dwarf Galaxy (if you count it as a galaxy), or the Large Magellanic Cloud. If I'm reading Wikipedia aright, those are the largest galaxies outside our own in visual angle. With a deep image, you might find a galaxy in a galaxy visible through one of those.
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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by Boomer12k » Sun Feb 09, 2014 2:16 am

Lovely wide shot...

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by neufer » Sun Feb 09, 2014 5:04 am

geckzilla wrote:
What I got from that is that somehow dark matter facilitates bar formation or bar stability. I'm not even going to pretend that I understand why a dark halo does this. :)
A spherical mass of constant density produces harmonic oscillating orbits of constant periodicity (where the orbital velocity is linearly proportional to the orbital radius).
This leads naturally to elliptical orbits around the center of the ellipse (not a foci) and, hence, the formation of stable bars.
http://www.nature.com/nature/journal/v422/n6931/fig_tab/422489a_F1.html wrote:
_The dark side_ by Masataka Fukugita
Nature 422, 489-491(3 April 2003)

:arrow: <<From observations of starlight alone, the rotational velocity of material in the arms of a spiral galaxy (such as M74, shown here) would be expected to fall exponentially towards the outer reaches of the galaxy (dashed line). In fact the curve flattens (solid line), suggesting that the galaxy is surrounded by a halo of unseen, dark matter.>>
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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by NGC3314 » Sun Feb 09, 2014 2:31 pm

tomatoherd wrote:As noted, there are distant galaxies visible through NGC 5101. The one at about 7 o'clock appears face-on, and very similar to NGC 5101 itself. It even seems to have darker, more rarified streaks within it. So what I find interesting is that if we are looking through this distant one, we are peering through THREE layers of galaxies: our own, NGC 5101, and the distant one.
Does anyone know of an example of FOUR layers???
One such is this picture of a distant galaxy pair. All but the brightest foreground stars are in the outer regions of the nearby spiral NGC 253. So we have the Milky Way, NGC 253, the foreground-background members of the galaxy pair, and all the very small galaxy images in the deep background. There is also a less-overlapping pair which shows up in a wide field arond M106.

Image

I was sure this had been an APOD circa 2009, but my search skills are failing me if so

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MargaritaMc » Sun Feb 09, 2014 2:59 pm

NGC3314 wrote:
tomatoherd wrote:As noted, there are distant galaxies visible through NGC 5101. The one at about 7 o'clock appears face-on, and very similar to NGC 5101 itself. It even seems to have darker, more rarified streaks within it. So what I find interesting is that if we are looking through this distant one, we are peering through THREE layers of galaxies: our own, NGC 5101, and the distant one.
Does anyone know of an example of FOUR layers???
One such is this picture of a distant galaxy pair. All but the brightest foreground stars are in the outer regions of the nearby spiral NGC 253. So we have the Milky Way, NGC 253, the foreground-background members of the galaxy pair, and all the very small galaxy images in the deep background. There is also a less-overlapping pair which shows up in a wide field arond M106.

I was sure this had been an APOD circa 2009, but my search skills are failing me if so

Here you are! NGC 253 on Apod.
http://apod.nasa.gov/apod/ap091121.html
Also
http://apod.nasa.gov/apod/ap111220.html

And here is M106, but I don't think that it's wide enough field to show the over-lapping pair:
http://apod.nasa.gov/apod/ap130206.html

Margarita


PS. This is info from Hubble Heritage about how the image that ngc3314 posted came about:
http://heritage.stsci.edu/2008/33/caption.html
Most of the stars speckled across this image belong to the nearby spiral galaxy NGC 253, which is out of view to the right. Astronomers used Hubble’s Advanced Camera for Surveys to snap images of NGC 253 when they spied the two galaxies in the background. From ground-based telescopes, the two galaxies look like a single blob. But the Advanced Camera’s sharp “eye” distinguished the blob as two galaxies, cataloged as 2MASX J00482185-2507365. The images were taken on Sept. 19, 2006.
Last edited by MargaritaMc on Sun Feb 09, 2014 3:08 pm, edited 1 time in total.
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by geckzilla » Sun Feb 09, 2014 3:04 pm

The overlapper appears at the lower right corner of the 2011 image of 253 but not in the other two. I don't think the overlapping pair itself has ever been featured. Hmm. I will have to keep an eye out for overlapping layers in the future.
Just call me "geck" because "zilla" is like a last name.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MargaritaMc » Sun Feb 09, 2014 3:20 pm

Here is something about 2MASX J00482185-2507365 (the image posted by ngc 3314) at the Galaxy Zoo blog
http://blog.galaxyzoo.org/2012/04/11/du ... m-arizona/
Interesting, but a bit far off topic to put a quote here.
M

PS. Regarding overlapping galaxies - we mustn't ignore ngc 3314's alter-ego. Probably THE most famous pair of overlapping galaxies:
http://en.wikipedia.org/wiki/NGC_3314 http://apod.nasa.gov/apod/ap110715.html
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by starsurfer » Wed Feb 12, 2014 4:15 pm

Another interesting overlapping pair is NGC 5544-5, seen below in an image by Adam Block.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MargaritaMc » Wed Feb 12, 2014 5:47 pm

Thanks for posting that beautiful image, starsurfer. Not only because it's so lovely, but also because it set me off exploring.
Bill Keel wrote about it, saying that:
This is one of the pairs we've used to trace the amount of dust in spiral galaxy disks, by taking advantage of the backlighting of a smooth and symmetric companion galaxy . http://www.astr.ua.edu/gifimages/ngc5544.html
That led me to his pages at the University of Alabama and this set of lecture notes entitled Dust in Galaxies

Margarita
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by NGC3314 » Thu Feb 13, 2014 4:35 am

:ssmile:

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by starsurfer » Thu Feb 13, 2014 8:49 am

Bill Keel is simply a wonderful man! I read many of his notes and explored his images many years ago.

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by MargaritaMc » Thu Feb 13, 2014 9:24 am

NGC3314 wrote::ssmile:
- Anon of Alabama?
They are very good notes!
M
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
&mdash; Dr Debra M. Elmegreen, Fellow of the AAAS

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Re: APOD: NGC 5101 and Friends (2014 Feb 08)

Post by Ann » Wed Feb 24, 2016 9:28 am

Just yesterday, I found a site that had named this image Space Porn Image of the Day 4/18/2014.

I have to agree, it really is a totally lovely image. Space porn - maybe. :wink:

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