APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

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Expand view Topic review: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Guest » Wed Apr 27, 2011 3:20 am

"From our perspective, the bright cores of the Arp 273 galaxies are separated by only a little over 100,000 light-years."

Is this a reference to einsteinian/lorentzian contraction?

(Apologies if you notice I'm being insulting: ) What is the separation from other perspectives?

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by bystander » Sat Apr 23, 2011 10:09 pm

geckzilla wrote:However, I am employing an "I'm too tired for fighting" attitude rather than a big stick policy.

I just figured I should point out that it's best not to go to war wielding a butter knife, when your opponent might be armed with tanks and stealth bombers.
If the visitor went back and actually read all of the posts (and the rules), he would find he was without ammunition (an apparent supply chain breakdown).
I never meant to start a fight in the first place. heh :(
I know, I never could figure out what the visitor was complaining about. I have a feeling he was trying to start a fight.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by geckzilla » Sat Apr 23, 2011 7:40 pm

However, I am employing an "I'm too tired for fighting" attitude rather than a big stick policy. I never meant to start a fight in the first place. heh :(

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by bystander » Sat Apr 23, 2011 6:12 pm

visitor wrote:I hope the moderators allow me to fight my own battles. If joining this forum is like being on trial then I want the right to cross examine.
You first have to join and become a member, rather than an anonymous troll.

FYI: the person you chose to pick a fight with (geckzilla) is the administrator of this board.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by visitor » Sat Apr 23, 2011 5:57 pm

geckzilla wrote:A nerve? I just prefer the innate complexity of science just the way it is. Actually, you might even say it's already "brought down" when it's posted to APOD every day. A paragraph of explanation isn't that much to chew on, though the embedded links do provide a lot of extra substance in most cases. I'm not even sure what you mean by "human level" ... at some point does science become inhuman?
Just saw your second post. Geckzilla, I get it. Anyone pathetic enough to get a kick out of seeing a rare image of the universe in in the colors of the visible light spectrum is a joke and beneath your contempt. But why are still picking apart my posts when you learned after the clarification in my second post that your presumption of my position was erroneous, that I am not ignorant of nor campaigning against the need for false-color imaging? What is it that are objecting to now that you know better? You pick apart my words like a partisan politician. What did I mean by "human level"? You really want to know? I meant the lack of human color perception in low light and the momentary desire to see the universe in a way the human eye cannot. Will this kind of image expand the knowledge base of science? Nope. It exists only for the pure, pointless enjoyment of those interested. I assume that this is the only reason APOD and the Hubble site occasionally show these images. The "human level" phrase was also going to be a set up for a crack and I thought better of it. Instead I went for truth and a mollyfying tone and said that it sure hit a nerve. Then you went after that phrase. Is ridicule your form of pure, pointless enjoyment? I will never object to clarifying my position.
Let's look at your second post in anything but a congenial way.
You say that you prefer the innate complexity of science "just the way it is". Does "just the way is is" mean you want it in grayscale? In raw data? In "visible light colors by travelling to dark enough place on a clear, cloudless night"? Do you mean that you are against assigning false colors to images? I'm new here, Is this what I am supposed to do on this forum? It's a cheap, lousy way to look smarter.

I hope the moderators allow me to fight my own battles. If joining this forum is like being on trial then I want the right to cross examine.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Hornet » Sat Apr 23, 2011 4:12 pm

The small inserted galaxy upper right does appear to be within the larger galaxy and appears to be interacting with the larger galaxy. It is possible that it may be a background galaxy but there are star bursts at suspicious locations suggesting interaction. could the smaller inserted galaxy be interacting but behind the larger galaxy???

I like thinking about their 'ultimate interaction' - suppose that the inserted galaxy is interacting: the inserted G spiral arms closest to the core of the larger G are moving with the larger G. The outside arms of the inserted G are moving opposite of the larger G - we have colliding gasses. new stars and much material falling into the larger G's Hole. Very interesting... Oh, I better stop, I might have a star-burst of brain activity. You don't want to see that.

That black hole is going to get fat.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by kshiarella » Fri Apr 22, 2011 3:21 am

Chris Peterson wrote:
flash wrote:I think I agree with Ann on this issue: At least for the "very faint light" sensitivity part of it. If we could imagine ourselves somehow transported much closer to these astonomical objects, the light they emit would be naturally amplified by the inverse square rule, and so become less faint, to the point where our eyes could actualy sense it. And in that case what we would see is more like Adam's images than Hubble's.
I'm afraid it doesn't work that way. These objects are not bright enough to show color to the human eye (or not much color). It doesn't matter how close you get, the brightness won't change. Why is that? Because as you get closer, the objects don't simply get brighter because of the inverse square law, they also get larger. Get half as far away and you'll get four times more light, but the object will have four times the area. Net result: no change in surface brightness. There is no difference at all between getting closer and observing the object at higher magnification through a telescope. In either case, virtually all extended astronomical objects are the same color: gray.
Another way to think about it is considering our own Milky Way. Although the stars of our own Galaxy are orders of magnitude closer from our vantage point, it is still a little more than a diffuse haze to the naked eye because the stars are correspondingly so much farther apart. The closer we would get to another galaxy, the less distinguishable from our own Milky Way it would become, at least to the naked eye.

It is more tantalizing and fantastic to think that we could get "close" to a fantastic celestial body like the "celestial event" imaged in the movie "Contact." It is sad to think that if we traveled to near the center of our own galaxy, that we would only see a particularly rich star field.

Imaging these galaxies in this way might be as spectacular as it gets.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by geckzilla » Fri Apr 22, 2011 1:44 am

Ah, so you mean the Greeks have a settlement in that Peculiar Galaxy.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Sam » Fri Apr 22, 2011 1:30 am

geckzilla wrote:You speak English and have an English word for it, huh? :lol:
Oxford English Dictionary wrote:
delta, n.

Etymology: < Greek δέλτα ( < Phoenician daleth), name of the fourth letter of the Greek alphabet; also the land at the mouth of the Nile (Herod.), the Indus (Strabo), etc.
1.a. The name of the fourth letter of the Greek alphabet, having the form of a triangle (Δ), and the power of D.
Image
http://asterisk.apod.com/viewtopic.php?f=9&t=22764


---
Sam

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by geckzilla » Fri Apr 22, 2011 12:53 am

visitor wrote:Geckzilla, nobody on this planet should ever have to apologize for bringing science down to any human level. It sure hit a nerve.
A nerve? I just prefer the innate complexity of science just the way it is. Actually, you might even say it's already "brought down" when it's posted to APOD every day. A paragraph of explanation isn't that much to chew on, though the embedded links do provide a lot of extra substance in most cases. I'm not even sure what you mean by "human level" ... at some point does science become inhuman?

Guest wrote:....the blue cluster is where i actually come from...we call it the draycon delta complex
You speak English and have an English word for it, huh? :lol:

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Guest » Fri Apr 22, 2011 12:50 am

....the blue cluster is where i actually come from...we call it the draycon delta complex

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by rstevenson » Fri Apr 22, 2011 12:31 am

visitor wrote:... No matter how breathtaking and highly detailed an image is, kids and adults alike ask Is that the real color? and they will continue to ask that question. ...
I rotate my desktop through hundreds of astro images. Occasionally a visitor will see some fantastic galaxy image and ask, "Is that what it really looks like?" At which point I open the image in a graphics program, pop up the colour controls, then dial the saturation down to where the image is essentially just black and white and gray. Then I say, "That's what it really looks like -- to our eyes." They're always disappointed. But then I explain about filters, and 10 hour exposures, and post-processing and such, and by the time they leave they appreciate the wonders of our technology as well as the wonders of the cosmos.

By the way, I almost always use that same saturation slider to partly desaturate (in the range of -20% to -30%, usually) the images I view on my desktop; I really don't like neon galaxies.

Rob

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Chris Peterson » Thu Apr 21, 2011 10:49 pm

visitor wrote:I thought that most who visit this site understand the use of synthetic palettes for images, Chris. I did not object to them or request that only the visible light spectrum be used.
Nor should my comment be taken as any sort of criticism. It was just an observation about the inherent value of false color palettes, even when the source data consists only of visible light images.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Chris Peterson » Thu Apr 21, 2011 10:44 pm

flash wrote:I think I agree with Ann on this issue: At least for the "very faint light" sensitivity part of it. If we could imagine ourselves somehow transported much closer to these astonomical objects, the light they emit would be naturally amplified by the inverse square rule, and so become less faint, to the point where our eyes could actualy sense it. And in that case what we would see is more like Adam's images than Hubble's.
I'm afraid it doesn't work that way. These objects are not bright enough to show color to the human eye (or not much color). It doesn't matter how close you get, the brightness won't change. Why is that? Because as you get closer, the objects don't simply get brighter because of the inverse square law, they also get larger. Get half as far away and you'll get four times more light, but the object will have four times the area. Net result: no change in surface brightness. There is no difference at all between getting closer and observing the object at higher magnification through a telescope. In either case, virtually all extended astronomical objects are the same color: gray.
In that sense Adam's images are more "true". Just because we cannot see an object with our eyes due to it's extreme distance does not mean that wavelength shifting is called for. Of course shifting is useful when viewing emissions that our eyes could not see no matter how intense.
In the case of imaging non-visible wavelengths, shifting isn't merely useful, it is essential! But as I said before, producing an image in "natural" colors is usually inappropriate for science purposes, because the color gamut of our eyes is poorly suited to observing most astronomical objects. For instance, there is a wide range of blue "colors" produced by stellar objects, but our eyes have very poor color resolution in blue. So by using a false color palette- shifting blues to greens or reds, for instance- we can discriminate much finer variations in the actual color. In other words, we can see physical differences between objects that would be invisible in a "natural" color palette. So unless the intent is purely aesthetic (which is fine, but is often not the case for astronomical images) there is good reason to use a false color palette in presenting images.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Ann » Thu Apr 21, 2011 10:21 pm

kshiarella wrote:
songwriterz wrote:Looking at the APOD (not the original photo) can anyone tell me what that blue structure is in the lower left corner?
I had the same question as well. Looking closely, there is faint yellow halo around the dense blue (ultraviolet?) core of the object in the lower left. I was guessing that it was an orbiting irregular galaxy. If it is a huge star cluster that has been cast out, is it a possible method of formation of irregular satellite galaxies that they represent a population of stars that were flung from a mother galaxy while in the process of interacting with a third?
Dwarf galaxies can definitely form that way. Take a look at this Hubble image of the Tadpole Galaxy, Arp 188. The blue clumps you can see in the Tadpole's tail are dwarf galaxies in the making:
However, I think that the stars in the blue clumps were not so much flung out of the parent galaxy as they were formed in situ out of gas that had been flung out of the parent galaxy. That's what I think about the two prominent blue clumps in today's APOD, too. Particularly the lower left structure is clumpy and irregular enough that I think it is made up of a large gas cloud that has given birth to a lot of stars, but there is still a lot of glowing gas left. So why would this gas cloud look blue and not pink from hydrogen emission? My answer would be that the filters that were chosen for this Hubble image does a relatively poor job at showing the pink emission nebula, so that, in fact, none are visible. But there can be no doubt that the larger galaxy, UGC 1810, does indeed contain pink dots of glowing nebulae. I think that if the Hubble people had imaged UGC 1810 through a hydrogen alpha filter, we would undoubtedly have seen very many pink knots in this galaxy, and I would guess that parts of the lower left blue clump would have been intensely pink.

I'm less certain of the "upper left blue clump". It is smoother and fainter than the other one, and I would guess that it is made up of slightly older and not quite so hot stars. I think it contains vary many stars, compared with the other blue clumps, but the brightest stars are somewhat fainter. This clump could perhaps be regarded as an established and slightly evolved dwarf galaxy.

Ann

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by visitor » Thu Apr 21, 2011 10:18 pm

geckzilla wrote:You can see a galaxy every night in visible light colors if you travel to a dark enough place on a clear, cloudless night. Personally, I would slighted if science was always "brought down" to whatever arbitrary common denominator for the sake of reducing confusion. Besides, if they suddenly started releasing nothing but visible light spectrum photos, Ann wouldn't have anything left to post about. :wink:
Chris Peterson wrote:[Even images taken only in visible light are often better displayed using synthetic palettes. Our eyes did not adapt for looking at galaxies, and we can often learn more about such objects by transforming their natural spectral output into artificial color spaces that allow us to extract much more information visually. In general, unless the intent is purely aesthetic, "natural" colors are usually not the best choice for astronomical objects.
I thought that most who visit this site understand the use of synthetic palettes for images, Chris. I did not object to them or request that only the visible light spectrum be used. I have lamented the fact that our eyes cannot see color in low light as perhaps you did when you first looked through a telescope at night and discovered the limitations of the human eye. Adam Block's photo allowed us to "see" what the human eye cannot. I delighted in it as I did the detailed, false-color image that was today's APOD. No matter how breathtaking and highly detailed an image is, kids and adults alike ask Is that the real color? and they will continue to ask that question. There is a legitimacy issue here whether it is an important one or not.

Geckzilla, nobody on this planet should ever have to apologize for bringing science down to any human level. It sure hit a nerve.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by flash » Thu Apr 21, 2011 8:43 pm

owlice wrote:
Except our eyes aren't "sensitive enough to very faint light." Adam's images are wonderful, but they aren't any more "true" than Hubble images, which show us "what our eyes would see, if they were sensitive enough to" ultraviolet light, because our eyes can't see either the "very faint light" nor the ultraviolet light.
I think I agree with Ann on this issue: At least for the "very faint light" sensitivity part of it. If we could imagine ourselves somehow transported much closer to these astonomical objects, the light they emit would be naturally amplified by the inverse square rule, and so become less faint, to the point where our eyes could actualy sense it. And in that case what we would see is more like Adam's images than Hubble's. In that sense Adam's images are more "true". Just because we cannot see an object with our eyes due to it's extreme distance does not mean that wavelength shifting is called for. Of course shifting is useful when viewing emissions that our eyes could not see no matter how intense.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by rstevenson » Thu Apr 21, 2011 7:29 pm

BMAONE23 wrote:Here is a link to the original Hi-res Hubble image (35 meg)
Eeeek! You just linked in the entire 35MB image. Fix it -- quick.

Rob

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by BMAONE23 » Thu Apr 21, 2011 7:25 pm

kshiarella wrote:
songwriterz wrote:Looking at the APOD (not the original photo) can anyone tell me what that blue structure is in the lower left corner?
I had the same question as well. Looking closely, there is faint yellow halo around the dense blue (ultraviolet?) core of the object in the lower left. I was guessing that it was an orbiting irregular galaxy. If it is a huge star cluster that has been cast out, is it a possible method of formation of irregular satellite galaxies that they represent a population of stars that were flung from a mother galaxy while in the process of interacting with a third?
Here is a link to the original Hi-res Hubble image (35 meg) (there is also a 62 meg version)
http://imgsrc.hubblesite.org/hu/db/imag ... es_jpg.jpg

The small blue region in the lower left corner resembles our own LMC or SMC satellite galaxy

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by kshiarella » Thu Apr 21, 2011 5:34 pm

songwriterz wrote:Looking at the APOD (not the original photo) can anyone tell me what that blue structure is in the lower left corner?
I had the same question as well. Looking closely, there is faint yellow halo around the dense blue (ultraviolet?) core of the object in the lower left. I was guessing that it was an orbiting irregular galaxy. If it is a huge star cluster that has been cast out, is it a possible method of formation of irregular satellite galaxies that they represent a population of stars that were flung from a mother galaxy while in the process of interacting with a third?

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by neufer » Thu Apr 21, 2011 4:59 pm

geckzilla wrote:
Did anyone notice the "mini spiral" in the upper right?
http://heritage.stsci.edu/2011/11/caption.html wrote:
A possible mini-spiral may be visible in the spiral arms of UGC 1810 to the upper right. It is noticeable how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars (reddish in color) on one side to clumpy and extremely blue on the other. The fairly regular spacing of the blue star-forming knots fits with what is seen in the spiral arms of other galaxies and is predictable based on instabilities in the gas contained within the arm.
http://wonderingminstrels.blogspot.com/2001/05/big-whorls-have-little-whorls-lewis-f.html wrote:
  • " Big whorls have little whorls
    That feed on their velocity,
    And little whorls have lesser whorls
    And so on to viscosity.
    "

    -- Lewis F Richardson
I first encountered this wonderful verselet in James Gleick's 'Chaos'
(highly recommended, incidentally - a very understandable and well-written
introduction to the topic), and was instantly captivated. The poem works on
two levels - both as a delightfully well-done parody of DeMorgan's famous
paraphrase of Swift, and as as nice a summation of the fractal nature of
turbulence as any I've seen. - martin

Biography:

Richardson, Lewis Fry
b. Oct. 11, 1881, Newcastle upon Tyne, Northumberland, Eng.
d. Sept. 30, 1953, Kilmun, Argyll, Scot.

British physicist and psychologist who was the first to apply mathematical
techniques to predict the weather accurately.

Richardson made major contributions to methods of solving certain types of
problems in physics, and from 1913 to 1922 he applied his ideas to
meteorology. His work, published in Weather Prediction by Numerical
Process (1922), was not entirely successful at first. The main drawback to
his mathematical technique for systematically forecasting the weather was
the time necessary to produce such a forecast. It generally took him three
months to predict the weather for the next 24 hours. With the advent of
electronic computers after World War II, his method of weather prediction,
somewhat altered and improved, became practical. The Richardson number,
a fundamental quantity involving the gradients (change over a distance)
of temperature and wind velocity, is named after him.
------------------------------------------------------------------------------------
http://en.wikipedia.org/wiki/Ad_infinitum wrote:
The 17th century writer Jonathan Swift mocked the idea of self-similarity in natural philosophy with the following lines in his poem 'On Poetry: A Rhapsody':
  • "So nat'ralists observe, a flea
    Hath smaller fleas that on him prey,
    And these have smaller fleas that bite 'em,
    And so proceed ad infinitum.
    "
The Victorian era mathematician Augustus De Morgan expanded on this with a similar verse:
  • "Great fleas have little fleas upon their backs to bite 'em,
    And little fleas have lesser fleas, and so ad infinitum.
    And the great fleas themselves, in turn, have greater fleas to go on,
    While these again have greater still, and greater still, and so on.
    "

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Chris Peterson » Thu Apr 21, 2011 3:48 pm

geckzilla wrote:You can see a galaxy every night in visible light colors if you travel to a dark enough place on a clear, cloudless night. Personally, I would slighted if science was always "brought down" to whatever arbitrary common denominator for the sake of reducing confusion. Besides, if they suddenly started releasing nothing but visible light spectrum photos, Ann wouldn't have anything left to post about. :wink:
Even images taken only in visible light are often better displayed using synthetic palettes. Our eyes did not adapt for looking at galaxies, and we can often learn more about such objects by transforming their natural spectral output into artificial color spaces that allow us to extract much more information visually. In general, unless the intent is purely aesthetic, "natural" colors are usually not the best choice for astronomical objects.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by geckzilla » Thu Apr 21, 2011 3:22 pm

Visitor wrote:Thanks, Ann, for understanding our need to bring science down to a human scale for better understanding and appreciation. I cannot explain why I would rather see the image in visible light colors other than the fact that I am not a bee. Assigned colors are OK as long as they are labeled as such. Thank you to Hubble for bringing it in such glorious detail.
You can see a galaxy every night in visible light colors if you travel to a dark enough place on a clear, cloudless night. Personally, I would slighted if science was always "brought down" to whatever arbitrary common denominator for the sake of reducing confusion. Besides, if they suddenly started releasing nothing but visible light spectrum photos, Ann wouldn't have anything left to post about. :wink:

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by Visitor » Thu Apr 21, 2011 3:06 pm

Thanks, Ann, for understanding our need to bring science down to a human scale for better understanding and appreciation. I cannot explain why I would rather see the image in visible light colors other than the fact that I am not a bee. Assigned colors are OK as long as they are labeled as such. Thank you to Hubble for bringing it in such glorious detail.

Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)

by geckzilla » Thu Apr 21, 2011 3:01 pm

cssbll wrote:
geckzilla wrote:
cssbll wrote:And the blue blob also to the left of the larger galaxy, which looks the same?
And that one looks like a distant background galaxy. The funny thing about these pictures is that a lot of the time all the stuff in the background doesn't even have a label or name. I like the red galaxy nestled mid-right between the two arms of the larger foreground galaxy.

but if it were, it should be red-shifted more. Doesn't have any discernable red-shift at all.
But one must admit that the texture of it is not consistent with the other clumps of bright young stars associated with the rest of the galaxy. It's very smooth and disc shaped.

Did anyone notice the "mini spiral" in the upper right?

http://heritage.stsci.edu/2011/11/caption.html
A possible mini-spiral may be visible in the spiral arms of UGC 1810 to the upper right. It is noticeable how the outermost spiral arm changes character as it passes this third galaxy, from smooth with lots of old stars (reddish in color) on one side to clumpy and extremely blue on the other. The fairly regular spacing of the blue star-forming knots fits with what is seen in the spiral arms of other galaxies and is predictable based on instabilities in the gas contained within the arm.

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