APOD: Stephan's Quintet (2021 Dec 18)

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APOD: Stephan's Quintet (2021 Dec 18)

Post by APOD Robot » Sat Dec 18, 2021 5:05 am

Image Stephan's Quintet

Explanation: The first identified compact galaxy group, Stephan's Quintet is featured in this eye-catching image constructed with data drawn from the extensive Hubble Legacy Archive. About 300 million light-years away, only four of these five galaxies are actually locked in a cosmic dance of repeated close encounters. The odd man out is easy to spot, though. The interacting galaxies, NGC 7319, 7318A, 7318B, and 7317 have an overall yellowish cast. They also tend to have distorted loops and tails, grown under the influence of disruptive gravitational tides. But the predominantly bluish galaxy, NGC 7320, is closer, just 40 million light-years distant, and isn't part of the interacting group. Stephan's Quintet lies within the boundaries of the high flying constellation Pegasus. At the estimated distance of the quartet of interacting galaxies, this field of view spans about 500,000 light-years. But moving just beyond this field, up and to the right, astronomers can identify another galaxy, NGC 7320C, that is also 300 million light-years distant. Including it would bring the interacting quartet back up to quintet status.

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VictorBorun
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by VictorBorun » Sat Dec 18, 2021 7:35 am

what, this whole field of view is 1/5 of Andromeda—Milky Way separation?

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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by Ann » Sat Dec 18, 2021 8:41 am

VictorBorun wrote: Sat Dec 18, 2021 7:35 am what, this whole field of view is 1/5 of Andromeda—Milky Way separation?
That sounds likely. Galaxy groups like Stephan's Quintet are tight.

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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by Ann » Sat Dec 18, 2021 9:25 am

HUBBLE_NGC7318_PS2_CROP_INSIGHT1024[1].jpg
Stephan's Quintet. North is to the right. Image Credit: NASA, ESA, Hubble Legacy Archive;
Processing & Copyright: Bernard Miller

Today's APOD is great. It really brings out excellent details in the galaxies of Stephan's Quintet! :D

1) NGC 7320: This is the foreground galaxy of Stephan's Quintet. We can tell at a glance that this a small, light-weight galaxy. The central region is small and faint, and consists of a mixture of old (yellow) and intermediate (yellow-white, white and bluish) stars. Large galaxies never have centers that are barely brighter than their disks! And unless there is a brilliant starburst at the centers of large galaxies - and even is there is! - they always have a bright yellow central population. As for the central "bulge" of NGC 7320, it is traced with short, fine dust lanes. At the very center is a tiny white spot, the nucleus. The disk is mottled with individual blue stars of, probably, in most cases spectral class B. The disk is of a relatively uniform brightness all over, and the spiral arms don't stand out very strongly against the disk.

2) NGC 7319: This is a barred grand design (two-armed) spiral galaxy with a long, broad, yellow bar. We can tell there is a bar because the arms start far away from the galactic center. The bar blends seamlessly into the large bulge. The center is bright white and spiral-shaped, and it is likely that there is star formation there. Dust is being ejected from the nucleus, possibly because of the black hole there. The arms are contorted by strong tidal forces. There are young stars and some star formation in the arms, particularly in one of the arms, but this is a predominantly yellow galaxy. A long, somewhat faint, blue tidal tail is stretching away from NGC 7319 towards the upper edge of the APOD.

3) NGC 7318 B: This is where most of the action is. NGC 7318 is a yellow spiral galaxy with a pair of short, barely bluish spiral arms, but there is also a long, prominent arc of dust, which is probably the remnant of a long, conspicuous spiral arm. NGC 7318 B is colliding with elliptical galaxy NGC 7318 A. Titanic forces of the collision have flung huge amounts of gas out of NGC 7318 B, and this gas has coalesced into large numbers of huge blue star clusters.

NGC 7317: This is an innocent-looking elliptical galaxy which appears to be unaffected by train wreck of the other galaxies. There is a small elongated object next to NGC 7317 whose redshift is the same as the redshift of NGC 7317, so this may be a tiny satellite of NGC 7317.


I would guess that NGC 7320, the foreground galaxy of Stephan's Quintet, is about the same size and mass as M33. The central regions and nuclei are similar. But the disk and arms of M33 are much "busier" than the disk and arms of NGC 7320.

Ann
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by orin stepanek » Sat Dec 18, 2021 12:00 pm

HUBBLE_NGC7318_PS2_CROP_INSIGHT1024.jpg
I'm probably wrong; but to me it looks almost like NGC7318 may
have been a pair already merged! :shock:
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by Fred the Cat » Sat Dec 18, 2021 3:55 pm

"Of all the gin joints in all the towns in all the world, she walks into mine" is about right for interacting galaxies. But you might expect more double-nucleus barred spirals would be reported. :?
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by neufer » Sat Dec 18, 2021 3:57 pm

APOD Robot wrote: Sat Dec 18, 2021 5:05 am
Explanation: But moving just beyond this field, up and to the right, astronomers can identify another galaxy, NGC 7320C, that is also 300 million light-years distant. Including it would bring the interacting quartet back up to quintet status.
https://en.wikipedia.org/wiki/Snow_angel wrote:
<<On March 28, 2007, Guinness World Records confirmed that North Dakota holds the world record for the most snow angels made simultaneously in one place. The event occurred on February 17, 2007, when 8,962 snow angels were created by people on the state capitol grounds in Bismarck. Previously, the record was held by Michigan Technological University with 3,784 students, locals, and alumni making snow angels on the school football field. Some birds (e.g. pheasants) leave on the snow a figure similar to a snow angel. Weddell seals often leave outlines of themselves, similar to a snow angel, melted into the ice.>>
https://en.wikipedia.org/wiki/Stephan%27s_Quintet wrote:




:arrow: NGC 7320C [bottom left in this image acquired with 17" PlaneWave CDK scope by W4SM in Louisa, VA] plowed through the Hickson association several hundred million years ago, pulling out the 100,000 light-year-long tail of gaseous debris from NGC 7319. The clusters in NGC 7319's streaming tail are 10 million to 500 million years old and may have formed at the time of the violent collision.











:arrow: This close-up view of Stephan's Quintet, a group of five galaxies, reveals a string of bright star clusters that sparkles like a diamond necklace. The clusters, each harboring up to millions of stars, were born from the violent interactions between some members of the group. The rude encounters also have distorted the galaxies' shapes, creating elongated spiral arms and long, gaseous streamers. This NASA Hubble Space Telescope photo showcases three regions of star birth: the long, sweeping tail and spiral arms of NGC 7319 [near center]; the gaseous debris of two galaxies, NGC 7318B and NGC 7318A [top right]; and the area north of those galaxies, dubbed the northern starburst region [top left]. The clusters' bluish color indicates that they're relatively young. Their ages span from about 2 million to more than 1 billion years old. The brilliant star clusters in NGC 7318B's spiral arm (about 30,000 light-years long) and the northern starburst region are between 2 million and more than 100 million years old. NGC 7318B instigated the starburst by barreling through the region. The bully galaxy is just below NGC 7318A at top right. Although NGC 7318B appears dangerously close to NGC 7318A, it's traveling too fast to merge with its close neighbor.

NGC 7320C triggered another collision that wreaked havoc. The faint bluish object at the tip of the tail is a young dwarf galaxy, which formed in the gaseous debris. The quintet is in the constellation Pegasus, 270 million light-years from Earth. The mosaic picture was taken by Hubble's Wide Field and Planetary Camera 2 on Dec. 30, 1998 and June 17, 1999.
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by alter-ego » Sun Dec 19, 2021 3:48 am

neufer wrote: Sat Dec 18, 2021 3:57 pm ...
Are you inferring Clarence graduated from a star to NGC 7320 after receiving his wings?
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by Ann » Sun Dec 19, 2021 4:33 am

There are is an interesting tail that seems to connect foreground galaxy NGC 7320 with background galaxy NGC 7320c:

Deep image of Stephans Quintet Matlas.png
Deep widefield image of Stephans Quintet annotated.png

As you can see, there appears to be a tail connecting foreground galaxy NGC 7320 with background galaxy NGC 7320c. It is of course highly likely that the tail actually stretches between NGC 7319 and NGC 7320c, which are at the same redshift, and that NGC 7320 just happens to block the view.

But it sure looks like...! Please note that the tail is thickest and bluest closest to the visible edge of the blue disk of NGC 7320. Read more here.

Well, Halton Arp would have had a field day looking at this tail! Just saying!

Ann
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by neufer » Sun Dec 19, 2021 1:37 pm

alter-ego wrote: Sun Dec 19, 2021 3:48 am
Are you inferring Clarence graduated from a star to NGC 7320 after receiving his wings?
  • NGC 7320Clarence Odbody dove in with the expectation
    that one of the Galaxy boys would dive in to rescue him.
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Re: APOD: Stephan's Quintet (2021 Dec 18)

Post by alter-ego » Tue Dec 21, 2021 4:15 am

neufer wrote: Sun Dec 19, 2021 1:37 pm
alter-ego wrote: Sun Dec 19, 2021 3:48 am
Are you inferring Clarence graduated from a star to NGC 7320 after receiving his wings?
  • NGC 7320Clarence Odbody dove in with the expectation
    that one of the Galaxy boys would dive in to rescue him.
:-? :facepalm:
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