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APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 4:06 am
by APOD Robot
Peculiar Galaxies of Arp 273
Explanation: The
spiky stars in the foreground of
this sharp cosmic portrait are well within our own
Milky Way Galaxy. The two eye-catching galaxies lie far
beyond the Milky Way, at a distance of over 300 million light-years. Their distorted appearance is due to gravitational tides as the pair engage
in close encounters. Cataloged
as Arp 273 (also as UGC 1810), the galaxies do look
peculiar, but interacting galaxies are now understood to be common in the universe. In fact, the nearby large spiral Andromeda Galaxy is known to be some 2 million light-years away and approaching the Milky Way. Arp 273 may offer an analog of their
far future encounter. Repeated galaxy encounters on a
cosmic timescale can ultimately result in a merger into a single galaxy of stars. From our perspective, the bright cores of the Arp 273 galaxies are separated by only a little over 100,000 light-years. The release of this
stunning vista celebrates the 21st anniversary of the Hubble Space Telescope in orbit.
[/b]
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 4:12 am
by Beyond
I think Peculiar Galaxies are Peculiarly NICE!
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 4:37 am
by bystander
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 5:55 am
by Ann
This is a splendid galaxy pair. The larger galaxy displays such an intricate spiral shape that it indeed resembles a rose. That is how Arp 273 is described on Hubblesite, as a "rose" of galaxies. The smaller galaxy would be the "stem", I guess!
As usual, the resolution of the Hubble image is stunning. In the larger galaxy, it is fascinating to compare the almost perfect smoothness of the inner arms with the increasing clumpiness of the outer arms, culminating in an outer "arm" composed entirely of newborn associations of hot massive stars. But more fascinating still is the small "mini-spiral" embedded in the far right part of the bluest arm of UGC 1810, as the largest galaxy is called. Note the yellowish bar structure of the mini-spiral!
To me, the color balance of any astronomy picture is always incredibly interesting. The color balance of the finished image is highly dependent on the filters used to produce the image. If you check out this link, you'll see a link showing you what wavelengths were used to produce the Hubble picture and how the wavelengths were mapped to produce the image:
http://imgsrc.hubblesite.org/hu/db/imag ... ge_web.jpg
To summarize, the filters used were 390 nm, corresponding to ultraviolet light, mapped as blue in the image, 475 nm, mapped as green in the image, and a broadband red filter, centered at 600 nm.
How did the choice of filters affect the overall color of the finished picture? Interestingly, a NASA page that I found,
http://eosweb.larc.nasa.gov/EDDOCS/Wave ... olors.html, claims that 475 nm, which is mapped as green in the image of Arp 273, is the typical wavelength of blue light:
The visible blue light has a wavelength of about 475 nm.
So what is blue to human eyes...
...was shown as green in the Hubble picture:
By showing invisible ultraviolet light as blue and visible blue light as green, the Hubble picture of NGC 273 has been "shifted to the green and away from the blue", compared with what the human eye would see, if our eyes were sensitive enough to extremely faint light. To put it differently, the Hubble image singles out the very hot stars, the O- and B-type stars, and shows them as blue, but it merges the blue A-type stars like Vega and Sirius with more low-mass stars of spectral type F, G and K and shows the combined light of them as generally whitish or yellow-white.
Let's compare the color balance of the Hubble image with the color balance of an RGB image. This picture by Adam Block was Astronomy Picture of the Day on November 15, 2008. Note the blue color of the arms of UGC 1810 in Adam Block's image:
Adam Block's image is, I repeat, more "true" to what our eyes would see, if they were sensitive enough to very faint light. The Hubble image specifically traces the hottest stars and contrasts them with lower-mass but still moderately massive stars stars like Vega and Sirius. And of course, the Hubble picture brings out fantastic detail.
Ann
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 11:41 am
by owlice
Ann wrote:By showing invisible ultraviolet light as blue and visible blue light as green, the Hubble picture of NGC 273 has been "shifted to the green and away from the blue", compared with what the human eye would see, if our eyes were sensitive enough to extremely faint light.
But our eyes are
not "sensitive enough to extremely faint light," AND our eyes cannot see the "invisible ultraviolet light" at all (which is why you referred to it as "invisible," of course). The colors in "extremely faint light" is as invisible to us as the ultraviolet light.
Ann wrote:Adam Block's image is, I repeat, more "true" to what our eyes would see, if they were sensitive enough to very faint light.
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.
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 11:43 am
by songwriterz
Looking at the APOD (not the original photo) can anyone tell me what that blue structure is in the lower left corner?
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 12:59 pm
by cssbll
by songwriterz ยป Thu Apr 21, 2011 11:43 am
Looking at the APOD (not the original photo) can anyone tell me what that blue structure is in the lower left corner?
And the blue blob also to the left of the larger galaxy, which looks the same?
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 1:02 pm
by geckzilla
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'm gonna go with stray chunk of stars from one of the two galaxies, as opposed to some other background object. And here's the cool part where if I am wrong someone will come and correct me.
![Smile :)](./images/smilies/icon_smile.gif)
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 1:03 pm
by orin stepanek
I saved today's APOD as a future background. I also made a shortcut to to Hubble Heritage site. Looks like a lot of interesting wallpaper available.
![Cool 8-)](./images/smilies/icon_cool.gif)
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 1:05 pm
by geckzilla
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.
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 1:52 pm
by BMAONE23
Ann wrote:This is a splendid galaxy pair. The larger galaxy displays such an intricate spiral shape that it indeed resembles a rose. That is how Arp 273 is described on Hubblesite, as a "rose" of galaxies. The smaller galaxy would be the "stem", I guess!
(snip)
Ann
@~ A rose of sorts
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 1:53 pm
by cssbll
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.
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 2:18 pm
by moonstruck
As beautiful as the Galaxies are just look at all the background galaxies. There must be hundreds visible and this is in just one direction. Wow, thanks Hubble.
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 2:22 pm
by moonstruck
I miss counted. There must be thousands.
![Neutral :|](./images/smilies/icon_neutral.gif)
Groping for trouts in a peculiar river.
Posted: Thu Apr 21, 2011 2:43 pm
by neufer
----------------------------------------------
Measure For Measure : Act I, scene II
..............................................
POMPEY: Yonder man is carried to prison.
MISTRESS OVERDONE: But what's his offence?
POMPEY: Groping for trouts in a peculiar river.
----------------------------------------------
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 3:01 pm
by geckzilla
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.
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 3:06 pm
by Visitor
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)
Posted: Thu Apr 21, 2011 3:22 pm
by geckzilla
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 :wink:](./images/smilies/icon_wink.gif)
Re: APOD: Peculiar Galaxies of Arp 273 (2011 Apr 21)
Posted: Thu Apr 21, 2011 3:48 pm
by Chris Peterson
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)
Posted: Thu Apr 21, 2011 4:59 pm
by neufer
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)
Posted: Thu Apr 21, 2011 5:34 pm
by kshiarella
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)
Posted: Thu Apr 21, 2011 7:25 pm
by BMAONE23
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)
Posted: Thu Apr 21, 2011 7:29 pm
by rstevenson
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)
Posted: Thu Apr 21, 2011 8:43 pm
by flash
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)
Posted: Thu Apr 21, 2011 10:18 pm
by visitor
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 :wink:](./images/smilies/icon_wink.gif)
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.