Starship Asterisk*

by **Chris Peterson** » Mon May 04, 2015 8:47 pm

ta152h0 wrote:so in regards to galactic spin axis, there is no " standard " direction to cue off but simply the way we see it . No giant Cartesian coordinate system of universe proportions.

There is some evidence of a correlation between the spin axes of galaxies in clusters along void walls in the large scale structure of the Universe. Maybe, maybe not. But as far as what we normally see in images, the orientation is random.

by **geckzilla** » Mon May 04, 2015 8:42 pm

ta152h0 wrote:so in regards to galactic spin axis, there is no " standard " direction to cue off but simply the way we see it . No giant Cartesian coordinate system of universe proportions.

Galaxy Zoo had a set of data which at first seemed like there might be a preference for spin direction, but it actually turned out that people were better at detecting spin one way than they were the other way. So the Universe doesn't care, but the people are biased.

by **ta152h0** » Mon May 04, 2015 8:14 pm

so in regards to galactic spin axis, there is no " standard " direction to cue off but simply the way we see it . No giant Cartesian coordinate system of universe proportions.

by **geckzilla** » Mon May 04, 2015 3:56 pm

Ann wrote:Thanks for the great Hubble image, Geck.

One fascinating detail of that image is how there is a sharp "border", seen as a change in both color and texture, between the bulge and the area immediately outside it.

If you haven't, be sure to click the image 1 and image 2 links to see just how much more data exists in the Hubble image. There is no ground-based alternative for widefield astronomy at this resolution. There are higher resolution ground-based observatories which have very narrow fields of view. I'm sure you remember ALMA's breathtaking view of HL Tau. Anyway, I think I have sufficiently made my point so I'll shut up now.

Something else to note about the processing of the image and how you are interpreting it: In reality, the galaxy's transition from outer areas to the core is a smooth gradient with no clear demarcation. What has happened here is that the dynamic range of both images has been destroyed so that the details in the core are more easily visible. I gave the Hubble image a similar treatment to Pugh's so it was easier to compare the two. The core has been darkened the most near the center and then the darkening adjustment tapers off the farther away from the core that you look. This has the effect of reducing the glare from the brightness of the core and letting us see the dust lanes more easily. There is a rather large cloud of H-alpha sitting directly on top of the nucleus that isn't apparent in almost any rendition of the galaxy. That's because it's very difficult to see in a color image but it is very apparent in black and white. Have a look.

: 658nm Hubble M51 Nucleus

by **Ann** » Mon May 04, 2015 11:07 am

geckzilla wrote:
Ann wrote:But I checked out the 846.3 KB file. Like David Leodis, I wasn't too impressed with the 846.3 KB Hubble file's resolution of the central parts of M51. I thought Martin Pugh's resolution of the filamentary dust lanes crossing the inner bulge was not particularly inferior to Hubble's 846.3 KB resolution.
You're missing out. I want to show you something I think is wonderful. The Hubble version of the Whirlpool is actually a mosaic of 6 fields, which is why it's so huge. Looking at it up close is very inspiring. Here is a 1000x1000 pixel square of the nucleus of the galaxy. For fun, I've included Martin's adjusted to cover the same area.

Click to view full size image 1 or image 2

...
whirlpool_core_pugh.jpg

whirlpool_core_hubble.jpg
[/hide]

Thanks for the great Hubble image, Geck.

One fascinating detail of that image is how there is a sharp "border", seen as a change in both color and texture, between the bulge and the area immediately outside it.

Ann

by **Chris Peterson** » Mon May 04, 2015 4:24 am

ta152h0 wrote:initial conditions like the Big Bang ? That giant first billiards game ?

Initial conditions like the net angular momentum of the matter (ordinary and dark) in the region where the galaxy formed. There's some evidence of regional structure in galactic spin axis orientation. But in general, the only reason we see a galaxy spinning one way or the other is because of the direction we're viewing it from.

by **ta152h0** » Mon May 04, 2015 4:15 am

initial conditions like the Big Bang ? That giant first billiards game ?

by **Chris Peterson** » Mon May 04, 2015 3:55 am

ta152h0 wrote:are galactic spin axis direction determined by gee whizz random occurrences over 13 plus billion years ?

Galactic spin direction is determined by initial conditions and which direction we're seeing them from.

by **geckzilla** » Mon May 04, 2015 3:52 am

Ann wrote:But I checked out the 846.3 KB file. Like David Leodis, I wasn't too impressed with the 846.3 KB Hubble file's resolution of the central parts of M51. I thought Martin Pugh's resolution of the filamentary dust lanes crossing the inner bulge was not particularly inferior to Hubble's 846.3 KB resolution.

You're missing out. I want to show you something I think is wonderful. The Hubble version of the Whirlpool is actually a mosaic of 6 fields, which is why it's so huge. Looking at it up close is very inspiring. Here is a 1000x1000 pixel square of the nucleus of the galaxy. For fun, I've included Martin's adjusted to cover the same area.

: Click to view full size image 1 or image 2

...

[/hide]

by **ta152h0** » Mon May 04, 2015 2:34 am

are galactic spin axis direction determined by gee whizz random occurrences over 13 plus billion years ?

by **Ann** » Mon May 04, 2015 1:54 am

DavidLeodis wrote:
geckzilla wrote:
DavidLeodis wrote:The "spiral arms and dust lanes" in the explanation is a link to an image of M51 in the Hubble NewsCenter website, but as there is no mention about that image with that of M51 in Martin Pugh's website then I assume that the latter image has not used the Hubble image data. If so then then it seems almost pointless using Hubble to acquire such an image if a ground-based telescope can produce such a superior image (and presumably those of many other astronomy images).
Martin Pugh's image is indeed quite nice but it doesn't come anywhere near the clarity and finer resolution of the Hubble image. Maybe you didn't look at the highest resolution images available on the website. Even the JPEG version is over 100 megs. http://hubblesite.org/newscenter/archiv ... ge/a/warn/
Thanks geckzilla for your input .

The highest resolution I had looked at was the 846.3 kB version in the Hubble NewsCenter release. I have not looked at the versions of the image available through the 'Highest-quality download options' in the release as they are massive file sizes and access to them is even discouraged in the release. I will therefore accept your statement that Martin's version "doesn't come anywhere near the clarity and finer resolution of the Hubble image".

I, too, decided against the massive 100+MB JPEG file and the even more massive 200+MB TIFF file.

But I checked out the 846.3 KB file. Like David Leodis, I wasn't too impressed with the 846.3 KB Hubble file's resolution of the central parts of M51. I thought Martin Pugh's resolution of the filamentary dust lanes crossing the inner bulge was not particularly inferior to Hubble's 846.3 KB resolution.

But I must say that I appreciated Hubble's ability to resolve blue giants and supergiants in the Whirlpool galaxy's arms.

Ann

by **geckzilla** » Sun May 03, 2015 7:44 pm

It's pretty obvious to me that Hubble's image quality is superior to this ground-based image even from the 846 kB version, though. Pugh's is deeper and shows more of the faintest structures, but Hubble's is much more detailed in the brighter areas. Those warnings are a bit archaic. If you've got a decent computer and a decent internet connection, you should be able to view the huge JPEG just fine. Probably better to save the file to your computer than view it directly in the browser, though.

by **DavidLeodis** » Sun May 03, 2015 5:21 pm

geckzilla wrote:
DavidLeodis wrote:The "spiral arms and dust lanes" in the explanation is a link to an image of M51 in the Hubble NewsCenter website, but as there is no mention about that image with that of M51 in Martin Pugh's website then I assume that the latter image has not used the Hubble image data. If so then then it seems almost pointless using Hubble to acquire such an image if a ground-based telescope can produce such a superior image (and presumably those of many other astronomy images).
Martin Pugh's image is indeed quite nice but it doesn't come anywhere near the clarity and finer resolution of the Hubble image. Maybe you didn't look at the highest resolution images available on the website. Even the JPEG version is over 100 megs. http://hubblesite.org/newscenter/archiv ... ge/a/warn/

Thanks geckzilla for your input

.

The highest resolution I had looked at was the 846.3 kB version in the Hubble NewsCenter release. I have not looked at the versions of the image available through the 'Highest-quality download options' in the release as they are massive file sizes and access to them is even discouraged in the release. I will therefore accept your statement that Martin's version "doesn't come anywhere near the clarity and finer resolution of the Hubble image".

by **DavidLeodis** » Sun May 03, 2015 5:10 pm

Chris Peterson wrote:
DavidLeodis wrote:In the information about the image that was brought up through the "like this one" link it states "additional 12 hours of AOX-acquired luminance". I've tried to find out what the acronym AOX stands for and the only likely one seems to be 'adsorbable organic halogens' (given as AOX). I would be grateful if someone could please let me know if that is correct, but if not what does AOX stands for in relation to the APOD.
The AO-X is a tip/tilt corrector made by SBIG ("AO" = "Active Optics"). It improves resolution by compensating for tracking errors, and in a limited away can reduce some seeing effects.

Thank Chris for your help, which is appreciated

.

I had thought that at least the OX part may be something to do with Oxygen as OIII filters are often mentioned in information about APOD images.

by **starsurfer** » Sun May 03, 2015 4:47 pm

Ann wrote:A picture of NGC 4151 by Antonio Fernandez[/url] clearly reveals the "bar-end enhancements" of that galaxy, even though the bar itself is too weak to be seen. Antonio's image also shows us that the bar-end enhancements of NGC 4151 are really the brightest part of a bluish ring surrounding the yellow bulge. I guess we are seeing such a bluish ring in the background galaxy near M51. What we don't see in that galaxy is a yellow center and spiral arms!

Ann

His name is actually Antonio Sánchez.

by **geckzilla** » Sun May 03, 2015 3:55 pm

DavidLeodis wrote:The "spiral arms and dust lanes" in the explanation is a link to an image of M51 in the Hubble NewsCenter website, but as there is no mention about that image with that of M51 in Martin Pugh's website then I assume that the latter image has not used the Hubble image data. If so then then it seems almost pointless using Hubble to acquire such an image if a ground-based telescope can produce such a superior image (and presumably those of many other astronomy images).

Martin Pugh's image is indeed quite nice but it doesn't come anywhere near the clarity and finer resolution of the Hubble image. Maybe you didn't look at the highest resolution images available on the website. Even the JPEG version is over 100 megs. http://hubblesite.org/newscenter/archiv ... ge/a/warn/

by **Chris Peterson** » Sun May 03, 2015 2:44 pm

DavidLeodis wrote:In the information about the image that was brought up through the "like this one" link it states "additional 12 hours of AOX-acquired luminance". I've tried to find out what the acronym AOX stands for and the only likely one seems to be 'adsorbable organic halogens' (given as AOX). I would be grateful if someone could please let me know if that is correct, but if not what does AOX stands for in relation to the APOD.

The AO-X is a tip/tilt corrector made by SBIG ("AO" = "Active Optics"). It improves resolution by compensating for tracking errors, and in a limited away can reduce some seeing effects.

by **DavidLeodis** » Sun May 03, 2015 2:11 pm

In the information about the image that was brought up through the "like this one" link it states "additional 12 hours of AOX-acquired luminance". I've tried to find out what the acronym AOX stands for and the only likely one seems to be 'adsorbable organic halogens' (given as AOX). I would be grateful if someone could please let me know if that is correct, but if not what does AOX stands for in relation to the APOD.

The "spiral arms and dust lanes" in the explanation is a link to an image of M51 in the Hubble NewsCenter website, but as there is no mention about that image with that of M51 in Martin Pugh's website then I assume that the latter image has not used the Hubble image data. If so then then it seems almost pointless using Hubble to acquire such an image if a ground-based telescope can produce such a superior image (and presumably those of many other astronomy images).

by **Beyond** » Sat May 02, 2015 5:46 pm

Ah, what's a half a billion years between friends?

by **Case** » Sat May 02, 2015 5:30 pm

Tszabeau wrote:Based on the relatively pristine shape of the larger galaxy, I am guessing that this collision is in its' early stages. Is that a reasonable guess?

Ethan Siegel has this to say about that:

Scienceblogs.com wrote:The fact that the larger, spiral-shaped galaxy is only slightly distorted very likely tells us that the elliptical galaxy is much lower in mass, while the intense evidence of star formation in the spiral and severe distortions in the smaller companion show that these two galaxies are in the middle stages of a merger. They’ve very likely already made their first pass through one another at some point about half-a-billion years ago, are decidedly gravitationally bound, and are coming back for another interaction. The entire merger process will likely take another two-to-three passes to complete.

First encounter could be called early stage, but I wouldn't say that about the second encounter.

by **Case** » Sat May 02, 2015 4:48 pm

Ann wrote:One of the most amazing background galaxies seen in the direction of a well-known bright galaxy can be seen near the top and slightly to the right in this picture. It looks much like a blue dumbbell, set inside a blue circle. What is it?

Too bad that the 0.05"/px 11477×7965px Hubble image of M51 is so much cropped narrow that it doesn't include this gem.
The best image of IC 4278 that I could find, was Adam Block's 0.3"/px 5200×3467px image of M51, as indexed by Google from Scienceblogs.com.

by **Boomer12k** » Sat May 02, 2015 12:39 pm

Ok, peridolia time..... The dust over the smaller galaxy.... I see a hot, FLEMINGO dancer.....no kidding....

:---(===) *

by **Boomer12k** » Sat May 02, 2015 12:31 pm

Awesome job, Matin!!!!
Very clear, and good detail....

:---(===) *

by **Tszabeau** » Sat May 02, 2015 12:13 pm

Based on the relatively pristine shape of the larger galaxy, I am guessing that this collision is in its' early stages . Is that a reasonable guess?

by **Ann** » Sat May 02, 2015 5:59 am

This is a very fine portrait of one of the most photographed galaxies in the sky. Personally I love how it brings out the various stellar populations in NGC 5194, or M51, the Whirlpool galaxy. Note how a fine lattice of dust lanes is crisscrossing the the small bright yellow bulge. Note how faithfully the blue clusters and pink nebulas outline the major spiral arm pattern, although raging fires of hot blue stars have broken the arm symmetry at about one o'clock. Note how the lower left arm seems to flare out at the end, revealing an intermediate to old underlying smooth population.

One of the most amazing background galaxies seen in the direction of a well-known bright galaxy can be seen near the top and slightly to the right in this picture. It looks much like a blue dumbbell, set inside a blue circle. What is it?

My guess is that the straight blue line of the "dumbbell" is a blue bar. An old image of NGC 7741 by Adam Block clearly reveals the straight blue bar of that galaxy. The background galaxy in today's APOD likely has a similar bar. So what are the "weights" of the dumbbell, then? I guess they are bar-end enhancements. A picture of NGC 4151 by Antonio Fernandez clearly reveals the "bar-end enhancements" of that galaxy, even though the bar itself is too weak to be seen. Antonio's image also shows us that the bar-end enhancements of NGC 4151 are really the brightest part of a bluish ring surrounding the yellow bulge. I guess we are seeing such a bluish ring in the background galaxy near M51. What we don't see in that galaxy is a yellow center and spiral arms!

Ann

Starship Asterisk*

APOD: M51: The Whirlpool Galaxy (2015 May 02)

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