APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

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APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by APOD Robot » Wed Nov 13, 2024 5:05 am

Image Barred Spiral Galaxy NGC 1365 from Webb

Explanation: A mere 56 million light-years distant toward the southern constellation Fornax, NGC 1365 is an enormous barred spiral galaxy about 200,000 light-years in diameter. That's twice the size of our own barred spiral Milky Way. This sharp image from the James Webb Space Telescope's Mid-Infrared Instrument (MIRI) reveals stunning details of this magnificent spiral in infrared light. Webb's field of view stretches about 60,000 light-years across NGC 1365, exploring the galaxy's core and bright newborn star clusters. The intricate network of dusty filaments and bubbles is created by young stars along spiral arms winding from the galaxy's central bar. Astronomers suspect the gravity field of NGC 1365's bar plays a crucial role in the galaxy's evolution, funneling gas and dust into a star-forming maelstrom and ultimately feeding material into the active galaxy's central, supermassive black hole.

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by AVAO » Wed Nov 13, 2024 6:16 am

APOD Robot wrote: Wed Nov 13, 2024 5:05 am Image Barred Spiral Galaxy NGC 1365 from Webb
[...]
Astronomers suspect the gravity field of NGC 1365's bar plays a crucial role in the galaxy's evolution, funneling gas and dust into a star-forming maelstrom and ultimately feeding material into the active galaxy's central, supermassive black hole.

The black hole must feel a bit lonely, all alone in the middle :|

Source: Spaceguy44 reddit

Click to view full size image 1 or image 2
Rem.: The color assignment for the MIRI used in this example is artistic and not scientific in order to emphasize the drama of the event - just4fun. Original data: NASA/ESA/CSA jac berne (flickr)

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Ann » Wed Nov 13, 2024 6:54 am

NGC 1365 is a very interesting and impressive galaxy, and JWST's MIRI image sheds new light on it.


A striking aspect of the inner core is the "eye shape" that is created by the dust lanes above and below the core. The central round yellowish light source between the dust lanes in the MIRI image could represent the pupil of an eye, and the dust lanes the eyelids.


The "eyelids" look extremely bright in far infrared light. The center of NGC 1365 also looks both bright and star-filled in an optical and infrared composite image from ESO and TIMER, but the dust lanes look quite different than in the JWST image (because the infrared filter used for the ESO/TIMER image did not detect MIRI's far infrared wavelengths at all):


The dust lanes, which are so bright in the MIRI image, are dark in the ESO/TIMER picture. On the other hand, dozens of bright white knots are seen that could be young star clusters. But are they?


In the GALEX image, blue represents hot ultraviolet stars, and yellow represents cooler stars. As you can see, the core of NGC 1365 is not bright blue at all, and there really does not appear to be very many new stars there.

There are two possible reasons for the apparent lack of young ultraviolet stars in the core of NGC 1365. One is that the dust lanes there simply don't form new stars at all. Not all dust lanes do. Consider the overlapping galaxy pair known as AM 1316-241:


Another possibility is that new star clusters are indeed forming in the bright dust lanes surrounding the core of NGC 1365, but the clusters are hidden by dust. On the whole, I find that unlikely. The formation of new star clusters in the dust lanes should disturb the dust and make it look "irregular", but we see no signs of any such disturbances.


Let's take a closer look at the core as seen by MIRI:

APOD 13 November 2024 detail annotated.png

Let's look at the objects in the core. The one farthest to the left is a round yellowish thing, that actually looks as if it could be the galactic core. Yes, but look at the red rays that appear to emerge from another location in the galactic center. They don't come from the yellowish knot at left. And since NGC 1365 is a Seyfert galaxy with an active core, I expect any light rays and jets from the central region to come from the core. That's why I surmised that the small bright knot to the lower left of the yellow knot is the actual core of the galaxy, and the yellowish object to the left of it would be a star cluster. Maybe a globular cluster?

Then again... the picture that AVAO, Jac, posted above does indeed suggest that what I called "the yellowish knot at left" is indeed the core of NGC 1365:


So I guess that the "red rays" seen in the MIRI image come from an intensely bright far infrared source. Perhaps a hidden cluster?

Finally, you can see a bright "swelling" at the end of one of the central dust lanes that in my opinion must be a relatively newborn star cluster.


To close, I want to show you a picture of NGC 1365 that shows the "true" brightness distribution of NGC 1365, where the brightest parts of the galaxy are the core and the inner bar:


If you have trouble seeing the inner bar of NGC 1365 (and not just the long bar between the spiral arms), here it is:


Finally, I want to remind everyone that I am a complete amateur. I love galaxies, and I love to try to understand why they are the way they are, and I love to compare them with other galaxies. I really do my best to try to understand what is going on, as long as I can understand it in a non-mathematical way.

But I am not a scientist and certainly not a researcher, and what I write here is not the gospel truth. Always remember that.

Ann
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by LasseH » Wed Nov 13, 2024 8:59 am

I studied all the red rays closely. They could not all originate in one intense source.
They don't all cross in one and the same point.
For one thing, two pairs of rays above the center (pointing at 12 and 1 o'clock) are parallel. Also, one pair below (pointing at 5 o'clock) are parallel.

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Christian G. » Wed Nov 13, 2024 12:39 pm

The supermassive black hole of NGC 1365 has been found to rotate close to the maximal possible speed, so just under the speed of light, based on measurements of the inner edge of the accretion disk; but wouldn't that be the case of all black holes with accretion disks? i.e. that matter spins increasingly faster as it nears the event horizon until reaching maximal speed every time?

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Chris Peterson » Wed Nov 13, 2024 1:26 pm

Christian G. wrote: Wed Nov 13, 2024 12:39 pm The supermassive black hole of NGC 1365 has been found to rotate close to the maximal possible speed, so just under the speed of light, based on measurements of the inner edge of the accretion disk; but wouldn't that be the case of all black holes with accretion disks? i.e. that matter spins increasingly faster as it nears the event horizon until reaching maximal speed every time?
Don't confuse the orbital speed of material falling into a black hole with the rotational velocity of the black hole itself. It's all rather complicated. A simple (Schwarzschild) black hole (which probably doesn't exist) has no spin (zero angular momentum) and has a "final orbit" radius of 1.5 times the event horizon radius. That's the point where a body in orbit reaches the speed of light. But for a rotating black hole (Kerr, angular momentum > 0) the metrics get complex and the radius of the event horizon gets smaller. I take it that by measuring the motion of the accretion disk, it was possible to infer the angular momentum and therefore rotational speed of the black hole.
Chris

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by HellCat » Wed Nov 13, 2024 3:44 pm

Ann wrote: Wed Nov 13, 2024 6:54 am
Finally, I want to remind everyone that I am a complete amateur. I love galaxies, and I love to try to understand why they are the way they are, and I love to compare them with other galaxies. I really do my best to try to understand what is going on, as long as I can understand it in a non-mathematical way.

But I am not a scientist and certainly not a researcher, and what I write here is not the gospel truth. Always remember that.

Ann
Dear Ann,
As a fellow galaxy lover, this is exactly why I came here today. Fantastic overview and photographic comparisons.
Also, even if you were a professionally paid researcher... their words still wouldn't be the gospel truth!
Your opinion and insights are just as valuable.
Steve
PS - also a lover of the scientific process.

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Ann » Wed Nov 13, 2024 4:46 pm

HellCat wrote: Wed Nov 13, 2024 3:44 pm
Ann wrote: Wed Nov 13, 2024 6:54 am
Finally, I want to remind everyone that I am a complete amateur. I love galaxies, and I love to try to understand why they are the way they are, and I love to compare them with other galaxies. I really do my best to try to understand what is going on, as long as I can understand it in a non-mathematical way.

But I am not a scientist and certainly not a researcher, and what I write here is not the gospel truth. Always remember that.

Ann
Dear Ann,
As a fellow galaxy lover, this is exactly why I came here today. Fantastic overview and photographic comparisons.
Also, even if you were a professionally paid researcher... their words still wouldn't be the gospel truth!
Your opinion and insights are just as valuable.
Steve
PS - also a lover of the scientific process.
Thank you so much, Steve! 😊

Ann
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Christian G. » Wed Nov 13, 2024 5:49 pm

Chris Peterson wrote: Wed Nov 13, 2024 1:26 pm
Christian G. wrote: Wed Nov 13, 2024 12:39 pm The supermassive black hole of NGC 1365 has been found to rotate close to the maximal possible speed, so just under the speed of light, based on measurements of the inner edge of the accretion disk; but wouldn't that be the case of all black holes with accretion disks? i.e. that matter spins increasingly faster as it nears the event horizon until reaching maximal speed every time?
Don't confuse the orbital speed of material falling into a black hole with the rotational velocity of the black hole itself. It's all rather complicated. A simple (Schwarzschild) black hole (which probably doesn't exist) has no spin (zero angular momentum) and has a "final orbit" radius of 1.5 times the event horizon radius. That's the point where a body in orbit reaches the speed of light. But for a rotating black hole (Kerr, angular momentum > 0) the metrics get complex and the radius of the event horizon gets smaller. I take it that by measuring the motion of the accretion disk, it was possible to infer the angular momentum and therefore rotational speed of the black hole.
Thanks! Most interesting. And this begs a further question for me: when you speak of the rotational speed of a black hole, er, what is rotating exactly? The singularity? The event horizon? A pure spinning "field" with no actual object spinning?

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Chris Peterson » Wed Nov 13, 2024 6:13 pm

Christian G. wrote: Wed Nov 13, 2024 5:49 pm
Chris Peterson wrote: Wed Nov 13, 2024 1:26 pm
Christian G. wrote: Wed Nov 13, 2024 12:39 pm The supermassive black hole of NGC 1365 has been found to rotate close to the maximal possible speed, so just under the speed of light, based on measurements of the inner edge of the accretion disk; but wouldn't that be the case of all black holes with accretion disks? i.e. that matter spins increasingly faster as it nears the event horizon until reaching maximal speed every time?
Don't confuse the orbital speed of material falling into a black hole with the rotational velocity of the black hole itself. It's all rather complicated. A simple (Schwarzschild) black hole (which probably doesn't exist) has no spin (zero angular momentum) and has a "final orbit" radius of 1.5 times the event horizon radius. That's the point where a body in orbit reaches the speed of light. But for a rotating black hole (Kerr, angular momentum > 0) the metrics get complex and the radius of the event horizon gets smaller. I take it that by measuring the motion of the accretion disk, it was possible to infer the angular momentum and therefore rotational speed of the black hole.
Thanks! Most interesting. And this begs a further question for me: when you speak of the rotational speed of a black hole, er, what is rotating exactly? The singularity? The event horizon? A pure spinning "field" with no actual object spinning?
Not really my area. I think it's something like your third suggestion, and less about some sort of actual "spin" than it is angular momentum (which make sense without any need for an object with some physical size). An event horizon can't spin because it's not a physical thing at all. Rotating black holes drag the region of spacetime around them.
Chris

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Wed Nov 13, 2024 6:52 pm

AVAO wrote: Wed Nov 13, 2024 6:16 am
APOD Robot wrote: Wed Nov 13, 2024 5:05 am Image Barred Spiral Galaxy NGC 1365 from Webb
[...]
Astronomers suspect the gravity field of NGC 1365's bar plays a crucial role in the galaxy's evolution, funneling gas and dust into a star-forming maelstrom and ultimately feeding material into the active galaxy's central, supermassive black hole.

The black hole must feel a bit lonely, all alone in the middle :|

...
Is it any different in any other galaxy with a central black hole?
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Wed Nov 13, 2024 7:39 pm

Ann wrote: Wed Nov 13, 2024 6:54 am NGC 1365 is a very interesting and impressive galaxy, and JWST's MIRI image sheds new light on it.


...
Let's take a closer look at the core as seen by MIRI:


APOD 13 November 2024 detail annotated.png

Image

Let's look at the objects in the core. The one farthest to the left is a round yellowish thing, that actually looks as if it could be the galactic core. Yes, but look at the red rays that appear to emerge from another location in the galactic center. They don't come from the yellowish knot at left. And since NGC 1365 is a Seyfert galaxy with an active core, I expect any light rays and jets from the central region to come from the core. That's why I surmised that the small bright knot to the lower left of the yellow knot is the actual core of the galaxy, and the yellowish object to the left of it would be a star cluster. Maybe a globular cluster?

...
Ann
Red rays or no, how can that clearly core-like dead center bright spot NOT be the core? Hmm, on second thought, maybe there are two cores!
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Ann » Wed Nov 13, 2024 8:33 pm

johnnydeep wrote: Wed Nov 13, 2024 7:39 pm
Ann wrote: Wed Nov 13, 2024 6:54 am NGC 1365 is a very interesting and impressive galaxy, and JWST's MIRI image sheds new light on it.


...
Let's take a closer look at the core as seen by MIRI:


APOD 13 November 2024 detail annotated.png

Image

Let's look at the objects in the core. The one farthest to the left is a round yellowish thing, that actually looks as if it could be the galactic core. Yes, but look at the red rays that appear to emerge from another location in the galactic center. They don't come from the yellowish knot at left. And since NGC 1365 is a Seyfert galaxy with an active core, I expect any light rays and jets from the central region to come from the core. That's why I surmised that the small bright knot to the lower left of the yellow knot is the actual core of the galaxy, and the yellowish object to the left of it would be a star cluster. Maybe a globular cluster?

...
Ann
Red rays or no, how can that clearly core-like dead center bright spot NOT be the core? Hmm, on second thought, maybe there are two cores!
I changed my mind, Johnny. I now believe that the bright yellowish spot is indeed the core, and the source from which the red rays appear is probably a hidden star cluster which is extremely bright in far infrared light.

I don't think it is possible for a galaxy to have two cores, unless the galaxy is a merger product where two galaxies have recently merged, or are in the process of merging.

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by AVAO » Wed Nov 13, 2024 8:47 pm

johnnydeep wrote: Wed Nov 13, 2024 6:52 pm
AVAO wrote: Wed Nov 13, 2024 6:16 am
APOD Robot wrote: Wed Nov 13, 2024 5:05 am Image Barred Spiral Galaxy NGC 1365 from Webb
[...]
Astronomers suspect the gravity field of NGC 1365's bar plays a crucial role in the galaxy's evolution, funneling gas and dust into a star-forming maelstrom and ultimately feeding material into the active galaxy's central, supermassive black hole.

The black hole must feel a bit lonely, all alone in the middle :|

...
Is it any different in any other galaxy with a central black hole?

Well, I'm not being entirely serious. If you want to see the surroundings of our cosmic queen in the near infrared, you have to "dim" the rest massively, which then means that the surroundings around the core area appear practically empty and dark. In reality: if you increase the brightness, the queen outshines all the crown jewels around her, but the star stream bar mentioned by Ann becomes clearly visible.

Click to view full size image 1 or image 2

biggg: https://live.staticflickr.com/65535/541 ... e661_o.jpg
Original data: NASA/ESA/CSA (JWST) jac berne (flickr)

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by AVAO » Wed Nov 13, 2024 8:56 pm

Ann wrote: Wed Nov 13, 2024 8:33 pm
johnnydeep wrote: Wed Nov 13, 2024 7:39 pm
Ann wrote: Wed Nov 13, 2024 6:54 am NGC 1365 is a very interesting and impressive galaxy, and JWST's MIRI image sheds new light on it.


...
Let's take a closer look at the core as seen by MIRI:


APOD 13 November 2024 detail annotated.png

Image

Let's look at the objects in the core. The one farthest to the left is a round yellowish thing, that actually looks as if it could be the galactic core. Yes, but look at the red rays that appear to emerge from another location in the galactic center. They don't come from the yellowish knot at left. And since NGC 1365 is a Seyfert galaxy with an active core, I expect any light rays and jets from the central region to come from the core. That's why I surmised that the small bright knot to the lower left of the yellow knot is the actual core of the galaxy, and the yellowish object to the left of it would be a star cluster. Maybe a globular cluster?

...
Ann
Red rays or no, how can that clearly core-like dead center bright spot NOT be the core? Hmm, on second thought, maybe there are two cores!
I changed my mind, Johnny. I now believe that the bright yellowish spot is indeed the core, and the source from which the red rays appear is probably a hidden star cluster which is extremely bright in far infrared light.

I don't think it is possible for a galaxy to have two cores, unless the galaxy is a merger product where two galaxies have recently merged, or are in the process of merging.

Ann

I completely agree with you, Ann.
The red rays only exist in mid-infrared (MIRI). The matter is clear in near-infrared (NIRCAM) images.


What a beauty. I would book that trip immediately :wink:
bigger: https://live.staticflickr.com/65535/541 ... 2ec9_o.jpg
Original data: NASA/ESA/CSA (JWST-NIRCAM) NGC 1365 core in Near-IR jac berne (flickr)
Last edited by AVAO on Thu Nov 14, 2024 5:28 am, edited 1 time in total.

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Wed Nov 13, 2024 9:52 pm

AVAO wrote: Wed Nov 13, 2024 8:56 pm
Ann wrote: Wed Nov 13, 2024 8:33 pm
johnnydeep wrote: Wed Nov 13, 2024 7:39 pm

Red rays or no, how can that clearly core-like dead center bright spot NOT be the core? Hmm, on second thought, maybe there are two cores!
I changed my mind, Johnny. I now believe that the bright yellowish spot is indeed the core, and the source from which the red rays appear is probably a hidden star cluster which is extremely bright in far infrared light.

I don't think it is possible for a galaxy to have two cores, unless the galaxy is a merger product where two galaxies have recently merged, or are in the process of merging.

Ann

I completely agree with you, Ann.
The red rays only exist in mid-infrared (MIRI). The matter is clear in near-infrared (NIRCAM) images.


What a beauty. I would book that trip immediately :wink:
bigger: https://live.staticflickr.com/65535/541 ... 2ec9_o.jpg
Original data: NASA/ESA/CSA (JWST-NIRCAM) jac berne (flickr)
Is that also NGC 1365? (Sadly, I often can't tell if the images you post are just alternate pics of the APOD or something else entirely. You are a bit oracular. 😊)
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by Ann » Thu Nov 14, 2024 4:56 am

AVAO wrote: Wed Nov 13, 2024 8:56 pm

I completely agree with you, Ann.
The red rays only exist in mid-infrared (MIRI). The matter is clear in near-infrared (NIRCAM) images.


What a beauty. I would book that trip immediately :wink:

bigger: https://live.staticflickr.com/65535/541 ... 2ec9_o.jpg
Original data: NASA/ESA/CSA (JWST-NIRCAM) jac berne (flickr)

Wow, Jac! That is extremely beautiful. And the dust lanes appear to be full of star clusters. Well, I would guess that most of those clusters can't be very young or ultraviolet-bright, because if they were, the dust lanes should be bright in the GALEX ultraviolet image, too.

Of course, the GALEX image is very low resolution. Also some (or many!) of the clusters may indeed be young, but their ultraviolet light is very strongly dimmed by the dust they are immersed in.

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by AVAO » Thu Nov 14, 2024 5:41 am

johnnydeep wrote: Wed Nov 13, 2024 9:52 pm
AVAO wrote: Wed Nov 13, 2024 8:56 pm
Ann wrote: Wed Nov 13, 2024 8:33 pm

I changed my mind, Johnny. I now believe that the bright yellowish spot is indeed the core, and the source from which the red rays appear is probably a hidden star cluster which is extremely bright in far infrared light.

I don't think it is possible for a galaxy to have two cores, unless the galaxy is a merger product where two galaxies have recently merged, or are in the process of merging.

Ann

I completely agree with you, Ann.
The red rays only exist in mid-infrared (MIRI). The matter is clear in near-infrared (NIRCAM) images.


What a beauty. I would book that trip immediately :wink:
bigger: https://live.staticflickr.com/65535/541 ... 2ec9_o.jpg
Original data: NASA/ESA/CSA (JWST-NIRCAM) jac berne (flickr)
Is that also NGC 1365? (Sadly, I often can't tell if the images you post are just alternate pics of the APOD or something else entirely. You are a bit oracular. 😊)

OK. We only see the core area of ​​NGC 1365 here as a combination of various NIRCAM images from the JWST.
And yes, I find the galaxy and its core region amazing, as it has amazingly different appearances in the different wavelength ranges - especially in the core area. WEBB in the near infrared allows us to look behind the dust clouds of HST.

NGC1365 Core with HST Credits for the ground-based image: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for the WFPC2 image: NASA and John Trauger (Jet Propulsion Laboratory) Credits for the NICMOS image: NASA, ESA, and C. Marcella Carollo (Johns Hopkins University and Columbia University)

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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Thu Nov 14, 2024 12:12 pm

AVAO wrote: Thu Nov 14, 2024 5:41 am
johnnydeep wrote: Wed Nov 13, 2024 9:52 pm
AVAO wrote: Wed Nov 13, 2024 8:56 pm


I completely agree with you, Ann.
The red rays only exist in mid-infrared (MIRI). The matter is clear in near-infrared (NIRCAM) images.


What a beauty. I would book that trip immediately :wink:
bigger: https://live.staticflickr.com/65535/541 ... 2ec9_o.jpg
Original data: NASA/ESA/CSA (JWST-NIRCAM) jac berne (flickr)
Is that also NGC 1365? (Sadly, I often can't tell if the images you post are just alternate pics of the APOD or something else entirely. You are a bit oracular. 😊)

OK. We only see the core area of ​​NGC 1365 here as a combination of various NIRCAM images from the JWST.
And yes, I find the galaxy and its core region amazing, as it has amazingly different appearances in the different wavelength ranges - especially in the core area. WEBB in the near infrared allows us to look behind the dust clouds of HST.

NGC1365 Core with HST Credits for the ground-based image: Allan Sandage (The Observatories of the Carnegie Institution of Washington) and John Bedke (Computer Sciences Corporation and the Space Telescope Science Institute) Credits for the WFPC2 image: NASA and John Trauger (Jet Propulsion Laboratory) Credits for the NICMOS image: NASA, ESA, and C. Marcella Carollo (Johns Hopkins University and Columbia University)
Thanks. And I see you also clarified what it was in your original post. Thank you!
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by fredk » Thu Nov 14, 2024 3:39 pm

It's not clear from the APOD caption or the Webb release, but the straight red rays near the centre of NGC 1365 in the APOD image are diffraction spikes due to the bright compact sources around the nucleus, not actual features in the galaxy.

They're more obvious as diffraction spikes in the partner image:

https://webbtelescope.org/contents/medi ... KDT5ATRD8C

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johnnydeep
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Thu Nov 14, 2024 5:04 pm

fredk wrote: Thu Nov 14, 2024 3:39 pm It's not clear from the APOD caption or the Webb release, but the straight red rays near the centre of NGC 1365 in the APOD image are diffraction spikes due to the bright compact sources around the nucleus, not actual features in the galaxy.

They're more obvious as diffraction spikes in the partner image:

https://webbtelescope.org/contents/medi ... KDT5ATRD8C
Hmm, I think you are probably correct. And now I feel a bit foolish for even considering they might be real structures.
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VictorBorun
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by VictorBorun » Sun Nov 17, 2024 4:42 pm

AVAO wrote: Wed Nov 13, 2024 6:16 am
Click to view full size image 1 or image 2
Rem.: The color assignment for the MIRI used in this example is artistic and not scientific in order to emphasize the drama of the event - just4fun. Original data: NASA/ESA/CSA jac berne (flickr)
I was expecting 3 bright sources of red JWST spikes to be the core and the 2 ends of the bar.
Barred Spiral Galaxy NGC 1365 from Webb 1+.jpg
If it is in fact so, then the end of the bar that is shown up and left is blocked in the human-visible wavelength range.
Barred Spiral Galaxy NGC 1365 from Webb 2+.jpg
Barred Spiral Galaxy NGC 1365 from Webb 2.jpg
...
Click to view full size image 1 or image 2
Then the dust lanes are in front of it, and the disk of of the galaxy is observed here like it is put on the ceiling overhead
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johnnydeep
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Sun Nov 17, 2024 5:07 pm

So, experts, what's the consensus: are those red "rays" real, or just JWST diffraction spike artifacts?
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fredk
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by fredk » Wed Nov 20, 2024 5:31 pm

I contacted the Webb news team about this. They agreed the release was confusing and say they'll try to make it clear that these are diffraction spikes in future releases.

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johnnydeep
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Re: APOD: Barred Spiral Galaxy NGC 1365 from Webb (2024 Nov 13)

Post by johnnydeep » Wed Nov 20, 2024 5:52 pm

fredk wrote: Wed Nov 20, 2024 5:31 pm I contacted the Webb news team about this. They agreed the release was confusing and say they'll try to make it clear that these are diffraction spikes in future releases.
Thanks!
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