APOD: Stephan's Quintet from Webb, Hubble,... (2022 Jul 18)

[APOD Robot]

Stephan's Quintet from Webb, Hubble, and Subaru

Explanation: OK, but why can't you combine images from Webb and Hubble? You can, and today's featured image shows one impressive result. Although the recently launched James Webb Space Telescope (Webb) has a larger mirror than Hubble, it specializes in infrared light and can't see blue -- only up to about orange. Conversely, the Hubble Space Telescope (Hubble) has a smaller mirror than Webb and can't see as far into the infrared as Webb, but can image not only blue light but even ultraviolet. Therefore, Webb and Hubble data can be combined to create images across a wider variety of colors. The featured image of four galaxies from Stephan's Quintet shows Webb images as red and also includes images taken by Japan's ground-based Subaru telescope in Hawaii. Because image data for Webb, Hubble, and Subaru are made freely available, anyone around the world can process it themselves, and even create intriguing and scientifically useful multi-observatory montages.

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[Ann]

Stephan's Quintet looks amazing in the combined Hubble, JWST and Subaru image, processed by Rob Gendler.

Stephan's Quintet from Webb, Hubble, and Subaru. Image Credit: Webb, Hubble, Subaru; NASA, ESA, CSA, NOAJ, STScI; Processing & Copyright: Robert Gendler

---

Stephan's Quintet by JWST's MIRI. Credit: NASA, ESA, CSA, STScI

But my favorite Stephan's Quintet image is the one by JWST's MIRI (Mid-infrared instrument). Just look at what it shows us!

So... the dust distribution in small foreground spiral-like galaxy NGC 7320 is not spiral-shaped. Note the little background galaxy that can be seen right through the disk of NGC 7320!

Galaxy NGC 7319, at top, has an accreting black hole at its center, and its accretion disk is brilliantly bright at mid-infrared wavelengths.

But the centers of galaxies NGC 7318A and NGC 7318B, whose collision has caused all the fireworks in Stephan's Quintet, look "quiet", dust-free and "uneventful" at MIRI's wavelengths.

Ann

[VictorBorun]

Stephan's Quintet looks amazing in the combined Hubble, JWST and Subaru image, processed by Rob Gendler.
But my favorite Stephan's Quintet image is the one by JWST's MIRI (Mid-infrared instrument). Just look at what it shows us!
Ann

No accounting for taste
In Russian it's more like Nor taste neither colour make comrade

To me, it's a crime for Rob Gendler to make white of mid-IR quasar NGC 7319
And why no green?
If we compress mid IR, near IR, visible and UV into one RGB pic, every thermal spectrum peak is to look some pure colour based on the temperature.
It's the narrowness of the visible band that makes stars look white (Sun), reddish or ever so slightly bluish.
Compress the spectrum scale, and any thermal spectrum peak would become narrow, acid-coloured

PS but I admire the precise overlaying by Rob Gendler. A great job!

PPS unhappy with white, I still appriciate how Gendler presented that mid-IR quasar NGC 7319.
Can we see these 2 pairs of curved jets?

[sc02492]

This is a pretty image, expertly processed. However, the red, visible light signal from Hubble (and other visible light sources) is now conflated with the IR signal(s) of JWST- that would be fine if they represented similar spatial and intensity distributions of light, but this isn't necessarily the case. Lumping them together in the red channel potentially compromises the ability to identify the independent and unique contribution of JWST compared to Hubble/visible light (which is what makes JWST exciting!). In my opinion, JWST data are more easily interpreted and appreciated when they stand on their own, (and/or perhaps presented as a rollover with visible light data so that the audience can explore the differences). Admittedly there is no right or wrong way to portray what is essentially an artistic representation of the data, as in this case.

Steve Cannistra
www.starrywonders.com

[AVAO]

This is a pretty image, expertly processed. However, the red, visible light signal from Hubble (and other visible light sources) is now conflated with the IR signal(s) of JWST- that would be fine if they represented similar spatial and intensity distributions of light, but this isn't necessarily the case. Lumping them together in the red channel potentially compromises the ability to identify the independent and unique contribution of JWST compared to Hubble/visible light (which is what makes JWST exciting!). In my opinion, JWST data are more easily interpreted and appreciated when they stand on their own, (and/or perhaps presented as a rollover with visible light data so that the audience can explore the differences). Admittedly there is no right or wrong way to portray what is essentially an artistic representation of the data, as in this case.

Steve Cannistra
www.starrywonders.com

I have a similar view. I think the optical spectrum should still be retained as a background in the case of overlays. Otherwise the whole thing ends in an illegible confusion of colors, even if it is scientifically correct in principle. If new wavelengths are added, these should be readable as an addition, e.g. via a corresponding rollover. Something like the one shown below, even if the colors are in that case only "synthetic"...


https://live.staticflickr.com/65535/522 ... a267_o.jpg
jac berne (flickr) Original data: NASA, ESA, CSA, STScI

[orin stepanek]

Amazing how many stars are hidden that JWST can show us!

Wow! Kitty looks very busy

[Chris Peterson]

This is a pretty image, expertly processed. However, the red, visible light signal from Hubble (and other visible light sources) is now conflated with the IR signal(s) of JWST- that would be fine if they represented similar spatial and intensity distributions of light, but this isn't necessarily the case. Lumping them together in the red channel potentially compromises the ability to identify the independent and unique contribution of JWST compared to Hubble/visible light (which is what makes JWST exciting!). In my opinion, JWST data are more easily interpreted and appreciated when they stand on their own, (and/or perhaps presented as a rollover with visible light data so that the audience can explore the differences). Admittedly there is no right or wrong way to portray what is essentially an artistic representation of the data, as in this case.

Steve Cannistra
www.starrywonders.com

You can't produce a color image from multichannel data that is going to clearly show the data from those channels. You can play with different palettes all day, but the bottom line is that you hide information and much of the convolution is irreversible.

On the whole, it is best to think of these releases as aesthetic, not scientific. We can glean some information from the color, we can learn a lot about structure, but if science is the goal, we need to work with each channel independently. We can't combine them into a single color image.

[De58te]

I am a bit confused. The Apod introduction states that the James Webb telescope can't see blue color, only up to orange. Yet the infrared picture of the nebula that Orin Stepanek posted and he attributed to the JWST still shows the blue portion of the nebula, although a little fainter, yet the orange part of the nebula has disappeared. Me thinks maybe that is a Hubble photo?

[Chris Peterson]

I am a bit confused. The Apod introduction states that the James Webb telescope can't see blue color, only up to orange. Yet the infrared picture of the nebula that Orin Stepanek posted and he attributed to the JWST still shows the blue portion of the nebula, although a little fainter, yet the orange part of the nebula has disappeared. Me thinks maybe that is a Hubble photo?

HST and JWST images are instantly distinguished from each other by looking at the diffraction spikes. While we can't say for absolute certainty that the IR image comes from the HST, we can know that it doesn't come from the JWST. (In fact, however, the near IR frame is an HST image.)

[AVAO]

This is a pretty image, expertly processed. However, the red, visible light signal from Hubble (and other visible light sources) is now conflated with the IR signal(s) of JWST- that would be fine if they represented similar spatial and intensity distributions of light, but this isn't necessarily the case. Lumping them together in the red channel potentially compromises the ability to identify the independent and unique contribution of JWST compared to Hubble/visible light (which is what makes JWST exciting!). In my opinion, JWST data are more easily interpreted and appreciated when they stand on their own, (and/or perhaps presented as a rollover with visible light data so that the audience can explore the differences). Admittedly there is no right or wrong way to portray what is essentially an artistic representation of the data, as in this case.

Steve Cannistra
www.starrywonders.com

You can't produce a color image from multichannel data that is going to clearly show the data from those channels. You can play with different palettes all day, but the bottom line is that you hide information and much of the convolution is irreversible.

On the whole, it is best to think of these releases as aesthetic, not scientific. We can glean some information from the color, we can learn a lot about structure, but if science is the goal, we need to work with each channel independently. We can't combine them into a single color image.

Your comment describes very precisely one of the basic problems in creating astronomical images according to scientific principles. However, I would not judge the multi-wavelength image produced by Robert Gendler as purely aesthetically and scientifically worthless and I hope that you can also agree with the following argument:

It is only the resulting pixelbased color values ​​that become meaningless. Even if several wavelength spectra are combined, scientific values can be generated if, for example, the overall structural appearance of astronomical objects is better visible.


Crab Nebula NASA / ESA

The example of Stephan's Quintet from today's APOD is extremely difficult to understand structurally and spatially. This is exactly where color differences like in Ann's example of the "small" background galaxy behind NGC 7320 help us to see this more clearly and thus to be able to understand it better.

[Chris Peterson]

This is a pretty image, expertly processed. However, the red, visible light signal from Hubble (and other visible light sources) is now conflated with the IR signal(s) of JWST- that would be fine if they represented similar spatial and intensity distributions of light, but this isn't necessarily the case. Lumping them together in the red channel potentially compromises the ability to identify the independent and unique contribution of JWST compared to Hubble/visible light (which is what makes JWST exciting!). In my opinion, JWST data are more easily interpreted and appreciated when they stand on their own, (and/or perhaps presented as a rollover with visible light data so that the audience can explore the differences). Admittedly there is no right or wrong way to portray what is essentially an artistic representation of the data, as in this case.

Steve Cannistra
www.starrywonders.com

You can't produce a color image from multichannel data that is going to clearly show the data from those channels. You can play with different palettes all day, but the bottom line is that you hide information and much of the convolution is irreversible.

On the whole, it is best to think of these releases as aesthetic, not scientific. We can glean some information from the color, we can learn a lot about structure, but if science is the goal, we need to work with each channel independently. We can't combine them into a single color image.

Your comment describes very precisely one of the basic problems in creating astronomical images according to scientific principles. However, I would not judge the multi-wavelength image produced by Robert Gendler as purely aesthetically and scientifically worthless and I hope that you can also agree with the following argument:

It is only the resulting pixelbased color values ​​that become meaningless. Even if several wavelength spectra are combined, scientific values can be generated if, for example, the overall structural appearance of astronomical objects is better visible.


Crab Nebula NASA / ESA

The example of Stephan's Quintet from today's APOD is extremely difficult to understand structurally and spatially. This is exactly where color differences like in Ann's example of the "small" background galaxy behind NGC 7320 help us to see this more clearly and thus to be able to understand it better.

I did not say color images were "worthless". Only that choosing a monotonic palette scheme as some kind of general rule is foolish and in many cases will produce less useful information than other palette choices.

And, if our goal is truly to understand as richly as possible the structure of the nebula, then color images are not the way to go about that.

[johnnydeep]

I am a bit confused. The Apod introduction states that the James Webb telescope can't see blue color, only up to orange. Yet the infrared picture of the nebula that Orin Stepanek posted and he attributed to the JWST still shows the blue portion of the nebula, although a little fainter, yet the orange part of the nebula has disappeared. Me thinks maybe that is a Hubble photo?

HST and JWST images are instantly distinguished from each other by looking at the diffraction spikes. While we can't say for absolute certainty that the IR image comes from the HST, we can know that it doesn't come from the JWST. (In fact, however, the near IR frame is an HST image.)

Well, aside from the diffraction spike clue, the caption on that image from the link says they are both from Hubble:

Comparison of the Carina Nebula in visible light (left) and infrared (right), both images by Hubble. In the infrared image, we can see more stars that weren't visible before. Credit: NASA/ESA/M. Livio & Hubble 20th Anniversary Team (STScI)

[johnnydeep]

I was all set to be flummoxed by the extra diffraction spikes in what I first thought was a Webb image! So, I was relieved to read that the other spikes must be from Hubble and/or Subaru!

[PDemosthenes]

I would love it if NASA would typically mention the span of an object. Usually in light years. most of us earth bounds have little understanding of how huge many of these objects are.

[VictorBorun]

I would love it if NASA would typically mention the span of an object. Usually in light years. most of us earth bounds have little understanding of how huge many of these objects are.

[VictorBorun]

I wonder what shines mid-IR and not near-IR in galactic cores; not just in Stephan's Quintet, but in Cartwheel trio, too.
Maybe cores have a lot of red/brown dwarfs we have never known about before?

[VictorBorun]

my attempt to fit the 3 high resolution pictures of Cartwheel trio and their mystical IR-cores

[VictorBorun]

hover versions

Click to view full size image 1 or image 2

Click to view full size image 1 or image 2

[johnnydeep]

I would love it if NASA would typically mention the span of an object. Usually in light years. most of us earth bounds have little understanding of how huge many of these objects are.

...

Except that the left most member of the quintet - NGC 7320 - is only 40 Mly away, and the other 4 members are an average of 300 Mly away. So, if NGC 7320 was moved to 300 Mly away in this view, it would appear 7.5 times smaller than it does here.

[ EDIT: I thought I had posted this 6 hours earlier, but apparently only "previewed" it and forgot to "submit" it. ]

[Ann]

I would love it if NASA would typically mention the span of an object. Usually in light years. most of us earth bounds have little understanding of how huge many of these objects are.

...

Except that the left most member of the quintet - NGC 7320 - is only 40 Mly away, and the other 4 members are an average of 300 Mly away. So, if NGC 7320 was moved to 300 Mly away in this view, it would appear 7.5 times smaller than it does here.

[ EDIT: I thought I had posted this 6 hours earlier, but apparently only "previewed" it and forgot to "submit" it. ]

Yeah! I've done that!

Ann

[VictorBorun]

my attempt to fit the 3 high resolution pictures of Stephan's Quintet quartet and their mystical IR-cores

[VictorBorun]

hover versions

Click to view full size image 1 or image 2

Click to view full size image 1 or image 2