APOD: M94: A Double Ring Galaxy (2023 Jun 07)

[APOD Robot]

M94: A Double Ring Galaxy

Explanation: Most galaxies don't have any rings of stars and gas -- why does M94 have two? First, spiral galaxy M94 has an inner ring of newly formed stars surrounding its nucleus, giving it not only an unusual appearance but also a strong interior glow. A leading origin hypothesis holds that an elongated knot of stars known as a bar rotates in M94 and has generated a burst of star formation in this inner ring. Observations have also revealed another ring, an outer ring, one that is more faint, different in color, not closed, and relatively complex. What caused this outer ring is currently unknown. M94, pictured here, spans about 45,000 light years in total, lies about 15 million light years away, and can be seen with a small telescope toward the constellation of the Hunting Dogs (Canes Venatici).

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[Ann]

M94: A Double Ring Galaxy. Image Credit & Copyright: Brian Brennan

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To me M94 looks more like a triple ring galaxy!

Anyway, it is interesting that someone has just brought up Hoag's Object, possibly because Biran Brennan's picture of M94 is somewhat reminiscent of Hoag's Object.

Hoag's Object: A Nearly Perfect Ring Galaxy Image Credit: NASA, ESA, Hubble; Processing: Benoit Blanco

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Fascinating!

Ann

[johnnydeep]

Why does the text describe the outer ring as "not closed"? It looks pretty closed to me in this image. Unless they're talking about the apparent bridge of stars/gas at 3 o'clock between it and the inner, more colorful area? [ And honestly, I really see only ONE ring here, the outer one, plus an inner much more complex more typical spiral-galaxy structure. ]

[VictorBorun]

Why does the text describe the outer ring as "not closed"? It looks pretty closed to me in this image. Unless they're talking about the apparent bridge of stars/gas at 3 o'clock between it and the inner, more colorful area? [ And honestly, I really see only ONE ring here, the outer one, plus an inner much more complex more typical spiral-galaxy structure. ]

other astropics see the outer ring as consisting of arcs of uneven brightness

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Click to view full size image 1 or image 2

[VictorBorun]

IR+UV don't see rings at all

So the outer doughnut is a treat that is hard to bring out.
Does this shape mimic a stellar system's Koiper's belt?
Does this shape reflect a thickening in dark matter halo?
Why is at angle to inner disk?

[VictorBorun]

Why does the text describe the outer ring as "not closed"? It looks pretty closed to me in this image. Unless they're talking about the apparent bridge of stars/gas at 3 o'clock between it and the inner, more colorful area? [ And honestly, I really see only ONE ring here, the outer one, plus an inner much more complex more typical spiral-galaxy structure. ]

My eye sees the difference between 3 o'clock zero gap and 9 o'clock tiny gap as a perspective effect.
Give the outer ring a full doughnut shape and you can see it too

[orin stepanek]

At first I thought it was the result of a galactic merger; but after
reading the APOD; I guess not!

[johnnydeep]

Why does the text describe the outer ring as "not closed"? It looks pretty closed to me in this image. Unless they're talking about the apparent bridge of stars/gas at 3 o'clock between it and the inner, more colorful area? [ And honestly, I really see only ONE ring here, the outer one, plus an inner much more complex more typical spiral-galaxy structure. ]

other astropics see the outer ring as consisting of arcs of uneven brightness

M94..jpgM94-.jpg

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Click to view full size image 1 or image 2

Yes, that image displays a "not closed" structure much more convincingly.

[johnnydeep]

Why does the text describe the outer ring as "not closed"? It looks pretty closed to me in this image. Unless they're talking about the apparent bridge of stars/gas at 3 o'clock between it and the inner, more colorful area? [ And honestly, I really see only ONE ring here, the outer one, plus an inner much more complex more typical spiral-galaxy structure. ]

My eye sees the difference between 3 o'clock zero gap and 9 o'clock tiny gap as a perspective effect.
Give the outer ring a full doughnut shape and you can see it too

Yes, I do see some structural "stuff" going on at both 3 and 9 o'clock.

[VictorBorun]

where is M94? where is M101?
Pretty close. M94 is in fact in the Council of Giants gathered around Milky Way and Andromeda while M101 is right next to the CoG.
I finally found something like a 3d map. Sadly it's only a video, not an online interactive 3d model, but you can slide the slider and find a clear view of the things.

Here is the flat view of the CoG on wiki:

Here is a pair of frames from the video:

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Click to view full size image 1 or image 2

[VictorBorun]

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Click to view full size image 1 or image 2

And here I hang the flat view of the CoG over a frame:

[VictorBorun]

07-Laniakea_(LofE07240) 10.jpg (21.08 KiB) Viewed 3507 times

07-Laniakea_(LofE07240) 11.jpg (30.76 KiB) Viewed 3507 times

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Click to view full size image 1 or image 2

[VictorBorun]

http://www.galaxies3d.org/section-download.htm
I am thick but finally got it, there is a 3d space map freeware

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Click to view full size image 1 or image 2

[VictorBorun]

So here is M94, in the middle* of the road to Virgo cluster and M87, and here is M101, jumping a little up to Local Void from where the 3d app is looking:

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Click to view full size image 1 or image 2

in fact it is M96/Leo in the middle of that road. M94 is one third of that road

[VictorBorun]

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Click to view full size image 1 or image 2