Explanation: Named for the southern constellation toward which most of its galaxies can be found, the Fornax Cluster is one of the closest clusters of galaxies. About 62 million light-years away, it's over 20 times more distant than our neighboring Andromeda Galaxy, but only about 10 percent farther along than the better known and more populated Virgo Galaxy Cluster. Seen across this three degree wide field-of-view, almost every yellowish splotch on the image is an elliptical galaxy in the Fornax cluster. Elliptical galaxies NGC 1399 and NGC 1404 are the dominant, bright cluster members toward the bottom center. A standout, large barred spiral galaxy, NGC 1365, is visible on the upper right as a prominent Fornax cluster member.
It is hard not to be struck by the contrast between all the yellow blobs of elliptical galaxies in the Fornax cluster and the large, majestic, gorgeously shaped blue barred spiral galaxy of NGC 1365. This magnificent spiral looks so large compared with all the yellow blobs of the other galaxies that it is hard not to think that NGC 1365 is a foreground object. But it would really seem that it is not, because there was a type Ia supernova in NGC 1365 in 2012, and that should be enough to pin down the distance to NGC 1365 with a reasonable amount of certainty.
And you have to watch Judy's, Geckzilla's, fantastic animation of the core of NGC 1365. Go to this page and find a link to the animation.
NGC 1365 is a huge galaxy, with a diameter of some 300,000 light-years. That makes it three times the size of the Milky Way! And different parts of NGC 1365 orbit at different speeds in a complicated way. Read about it here!
There are two other interesting galaxies in the Fornax Cluster, and they are NGC 1399 and NGC 1427A. NGC 1399 is the largest elliptical galaxy of the Fornax Cluster, or the cD (central dominant) galaxy of the cluster.
I recommend that you look at the 780 KB version of the picture of NGC 1399, which is here. And if you are adventurous, I think you should look at the 22 MB version of the picture. If you do, you will see what looks like a rich sprinkling of round white salt flakes all over the image. These are globular clusters. NHC 1399 has a huge number of globular clusters, between 5700 and 6500 of them! Bear in mind that the Milky Way is estimated to only have some 200 globulars!
Another hugely interesting galaxy of the Fornax Cluster is just barely seen in today's APOD, as a tiny arc-shaped blue little thing at the very bottom edge of the APOD, slightly to the right of center. This is NGC 1427A. You can see it a bit better here, at about 9 o'clock:
Actually, NGC 1427A is a small and gas-rich galaxy helplessly falling into the Fornax Cluster, setting up a firestorm of star formation and almost burning up in the process!
I guess that if the Earth is the Pale Blue Dot, then NGC 1427A is the Poor Blue Blob. It is a hard life out there in the large galaxy clusters!
Ann
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Thu Nov 02, 2023 5:12 pm
by Roy
Ann’s explication seems to highlight several galaxy/cluster principal organization modes. Globe mode, spiral/rotational mode, and disorganized mode. Why is the cosmos organized thusly, as far as we can see?
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Thu Nov 02, 2023 6:53 pm
by Chris Peterson
Roy wrote: ↑Thu Nov 02, 2023 5:12 pm
Ann’s explication seems to highlight several galaxy/cluster principal organization modes. Globe mode, spiral/rotational mode, and disorganized mode. Why is the cosmos organized thusly, as far as we can see?
Keep in mind that we're not seeing static structures, but bodies in complex orbits around each other. How they appear to our brief snapshot view is not representative of any real structure. It's transient. Come back in a few hundred million years and these clusters will look very different, with very different apparent structures.
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Roy wrote: ↑Thu Nov 02, 2023 5:12 pm
Ann’s explication seems to highlight several galaxy/cluster principal organization modes. Globe mode, spiral/rotational mode, and disorganized mode. Why is the cosmos organized thusly, as far as we can see?
Keep in mind that we're not seeing static structures, but bodies in complex orbits around each other. How they appear to our brief snapshot view is not representative of any real structure. It's transient. Come back in a few hundred million years and these clusters will look very different, with very different apparent structures.
Do elliptical, spiral and irregular galaxies morph into each other over time? Merging spirals can form ellipticals I think, but are there other transformations? Irregulars growing into either spirals or ellipticals?
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Thu Nov 02, 2023 9:17 pm
by johnnydeep
Besides the nice galaxies Ann pointed out above, this odd looking "three bead" galaxy caught my eye:
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Roy wrote: ↑Thu Nov 02, 2023 5:12 pm
Ann’s explication seems to highlight several galaxy/cluster principal organization modes. Globe mode, spiral/rotational mode, and disorganized mode. Why is the cosmos organized thusly, as far as we can see?
Keep in mind that we're not seeing static structures, but bodies in complex orbits around each other. How they appear to our brief snapshot view is not representative of any real structure. It's transient. Come back in a few hundred million years and these clusters will look very different, with very different apparent structures.
Do elliptical, spiral and irregular galaxies morph into each other over time? Merging spirals can form ellipticals I think, but are there other transformations? Irregulars growing into either spirals or ellipticals?
There's a lot that isn't known about galaxy formation. But broadly, I don't think anything morphs into a spiral (unless it's a process very early in galaxy formation). It's possible that some non-spiral galaxies formed that way, but when a spiral is tidally disrupted, it commonly becomes an elliptical or irregular galaxy.
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Thu Nov 02, 2023 10:28 pm
by Pastorian
johnnydeep wrote: ↑Thu Nov 02, 2023 9:17 pm
Besides the nice galaxies Ann pointed out above, this odd looking "three bead" galaxy caught my eye:
odd looking galaxy in the fornax cluster - three beads.png
I browsed the CDS Portal - I'm fairly sure the galaxy you're referring to is NGC 1380, position: 03 36 27.828 -34 58 33.85. The cause of the beaded appearance becomes more clear in this excellent HST image:
Another intriguing find from today's thread is the face-on spiral to the 10 o'clock of NGC 1427A in the HST image that Ann posted:
Ann wrote: ↑Thu Nov 02, 2023 6:58 am
Another hugely interesting galaxy of the Fornax Cluster is just barely seen in today's APOD, as a tiny arc-shaped blue little thing at the very bottom edge of the APOD, slightly to the right of center. This is NGC 1427A. You can see it a bit better here, at about 9 o'clock:
Browsing the CDS Portal, it appears to be designated as 2MASX J03400430-3536514, and I would expect that it is not a part of the Fornax Cluster. Not sure yet how to determine distances from the data on the portal.
PS: CDS Portal (http://cdsportal.u-strasbg.fr/) is next level, bringing a whole interactive aspect for this armchair astronomer. Glad to have read about it on these boards a while back.
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
johnnydeep wrote: ↑Thu Nov 02, 2023 9:17 pm
Besides the nice galaxies Ann pointed out above, this odd looking "three bead" galaxy caught my eye:
odd looking galaxy in the fornax cluster - three beads.png
I browsed the CDS Portal - I'm fairly sure the galaxy you're referring to is NGC 1380, position: 03 36 27.828 -34 58 33.85. The cause of the beaded appearance becomes more clear in this excellent HST image:
Yup, that's it alright, but it looks completely different in that center region closeup!
Another intriguing find from today's thread is the face-on spiral to the 10 o'clock of NGC 1427A in the HST image that Ann posted:
'''
Browsing the CDS Portal, it appears to be designated as 2MASX J03400430-3536514, and I would expect that it is not a part of the Fornax Cluster. Not sure yet how to determine distances from the data on the portal.
Yup, that's a nice one!
PS: CDS Portal (http://cdsportal.u-strasbg.fr/) is next level, bringing a whole interactive aspect for this armchair astronomer. Glad to have read about it on these boards a while back.
Nice. I'll save a link.
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Thu Nov 02, 2023 11:35 pm
by orin stepanek
NGC1365; What a beauty! Upper Right!
Not seeing Andromeda here!
Ah! NGC1365 from JWST; so beautiful
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Fri Nov 03, 2023 5:59 am
by Ann
johnnydeep wrote: ↑Thu Nov 02, 2023 9:17 pm
Besides the nice galaxies Ann pointed out above, this odd looking "three bead" galaxy caught my eye:
I'll reserve judgement on whether or not the "three bead galaxy" really is NGC 1380. Admittedly it could be, although it does look quite different in the picture posted by Pastorian. It is true that some lenticular galaxies, which otherwise lack dust or star formation, may have a small dust ring near their cores.
But often, when we see a "three-bead" galaxy, we are seeing what I would call a former barred spiral galaxy that has lost its ability to form new stars. All its stars have grown old and yellow, and the galaxy has lost its spiral arms and its dust lanes.
But a three-bead galaxy may have started out like this:
Galaxy NGC 1300. You can see its core, its bar and its bar-end enhancement.
These are found where the bar-ends meet the spiral arms. They typically
contain a high amount of star formation.
When the galaxy grows old, the bar-end enhancements may remain bright.
Keep in mind that we're not seeing static structures, but bodies in complex orbits around each other. How they appear to our brief snapshot view is not representative of any real structure. It's transient. Come back in a few hundred million years and these clusters will look very different, with very different apparent structures.
Do elliptical, spiral and irregular galaxies morph into each other over time? Merging spirals can form ellipticals I think, but are there other transformations? Irregulars growing into either spirals or ellipticals?
There's a lot that isn't known about galaxy formation. But broadly, I don't think anything morphs into a spiral (unless it's a process very early in galaxy formation). It's possible that some non-spiral galaxies formed that way, but when a spiral is tidally disrupted, it commonly becomes an elliptical or irregular galaxy.
Which way?
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Do elliptical, spiral and irregular galaxies morph into each other over time? Merging spirals can form ellipticals I think, but are there other transformations? Irregulars growing into either spirals or ellipticals?
There's a lot that isn't known about galaxy formation. But broadly, I don't think anything morphs into a spiral (unless it's a process very early in galaxy formation). It's possible that some non-spiral galaxies formed that way, but when a spiral is tidally disrupted, it commonly becomes an elliptical or irregular galaxy.
Which way?
The way they are... as ellipticals or irregulars.
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Chris Peterson wrote: ↑Thu Nov 02, 2023 9:23 pm
There's a lot that isn't known about galaxy formation. But broadly, I don't think anything morphs into a spiral (unless it's a process very early in galaxy formation). It's possible that some non-spiral galaxies formed that way, but when a spiral is tidally disrupted, it commonly becomes an elliptical or irregular galaxy.
Which way?
The way they are... as ellipticals or irregulars.
Ah - "Formed that way, not "formed that way"! D'oh!
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
johnnydeep wrote: ↑Thu Nov 02, 2023 9:17 pm
Besides the nice galaxies Ann pointed out above, this odd looking "three bead" galaxy caught my eye:
odd looking galaxy in the fornax cluster - three beads.png
I browsed the CDS Portal - I'm fairly sure the galaxy you're referring to is NGC 1380, position: 03 36 27.828 -34 58 33.85. The cause of the beaded appearance becomes more clear in this excellent HST image:
I browsed the CDS Portal - I'm fairly sure the galaxy you're referring to is NGC 1380, position: 03 36 27.828 -34 58 33.85. The cause of the beaded appearance becomes more clear in this excellent HST image:
And just to be clear, that diffuse white "fog" of a halo surrounding the galaxy cores in these images is composed of stars, not just gas, correct?
Since these images are visible-light images, the white stuff surrounding the galaxy cores are most definitely stars. Because gas doesn't glow at visible wavelengths unless it's being ionized and made to emit light at visible wavelengths. And there is nothing here that could create that sort of large-scale ionization.
There might, for all I know, be a ubiquitous glow of extremely faint hydrogen alpha emission all over and inside this galaxy. But it would be way, way, way too faint to show up here. But it is far, far from certain that there is any appreciable amount of any such hydrogen alpha surrounding these elliptical and lenticular galaxies at all. Take a look at this LRGB + H-alpha picture of Markarian's Chain in the Virgo Cluster:
The Virgo Cluster of galaxies in LRGB and 33 hours of H-alpha.
Note the red tendril between disturbed spiral NGC 4438 and elliptical M86.
Credit: Jakob Sahner.
You can see that, apart from the bridge of ionized hydrogen between NGC 4438 and M86, there isn't a lot of visible red gas in the Virgo Cluster. Not in a 33 hours of H-alpha exposure image, at least.
However, there may be million-degree gas surrounding NGC 1380. There exists no Chandra X-ray telescope image showing us NGC 1380, but there is a Chandra X-ray picture of the central massive elliptical galaxy, NGC 1399, and two other elliptical galaxies close to it:
But this million-degree gas is only visible to telescopes like Chandra. So, conclusion, the white stuff we can see in the images you asked about is stars, and stars only.
Ann
Re: APOD: The Fornax Cluster of Galaxies (2023 Nov 02)
Posted: Sun Nov 05, 2023 2:29 pm
by johnnydeep
Ann said:
So, conclusion, the white stuff we can see in the images you asked about is stars, and stars only.
Thanks. And yes, I am always amazed by this fact. Stars, stars, oh so many blazing stars!
The Fornax Cluster of Galaxies
