APOD: Messier 66 Close Up (2021 Jan 28)

Comments and questions about the APOD on the main view screen.
User avatar
APOD Robot
Otto Posterman
Posts: 4482
Joined: Fri Dec 04, 2009 3:27 am

APOD: Messier 66 Close Up (2021 Jan 28)

Post by APOD Robot » Thu Jan 28, 2021 5:05 am

Image Messier 66 Close Up

Explanation: Big, beautiful spiral galaxy Messier 66 lies a mere 35 million light-years away. The gorgeous island universe is about 100 thousand light-years across, similar in size to the Milky Way. This reprocessed Hubble Space Telescope close-up view spans a region about 30,000 light-years wide around the galactic core. It shows the galaxy's disk dramatically inclined to our line-of-sight. Surrounding its bright core, the likely home of a supermassive black hole, obscuring dust lanes and young, blue star clusters sweep along spiral arms dotted with the tell-tale glow of pinksh star forming regions. Messier 66, also known as NGC 3627, is the brightest of the three galaxies in the gravitationaly interacting Leo Triplet.

<< Previous APOD This Day in APOD Next APOD >>

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Thu Jan 28, 2021 10:46 am

Structures of M66.png
M66 has a "squashed S-shape that is unmistakable. I have marked the S-shape in yellow in the attachment to the right.

But M66 also has a broad "blue flow" of bright stars just below the dust lane framing the yellow bar. I have marked the "blue flow" in blue in the attachment at right.

M66_Hubble_LeoShatz_Crop1024[1].jpg
M66 close up. NASA, ESA, Hubble; Processing & Copyright: Leo Shatz
The field of view in the APOD isn't wide enough to let us see all of M66. But the way the arms turn sharply at the ends of the bar is a good indication that the galaxy is M66.

But really, the unmistakable sign that this galaxy is M66 is the "blue flow" of stars below center in the APOD. The only other galaxy I know of off-hand that has an even slightly similar "blue flow" of stars is M106. But in M106, the blue flow is not located in the same place, and it is not as bright.

Finally, it must be pointed out that M66 is a member of a galactic triplet, the Leo triplet. The other two members M65 and NGC 3628.

Ann
You do not have the required permissions to view the files attached to this post.
Color Commentator

User avatar
orin stepanek
Plutopian
Posts: 6994
Joined: Wed Jul 27, 2005 3:41 pm
Location: Nebraska

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by orin stepanek » Thu Jan 28, 2021 1:17 pm

M66_Hubble_LeoShatz_Crop1024.jpg
Wow! Look at all the stars that are so far away! Bogs my mind that we can see them so clearly in a galaxy so far away! Just beautiful!!! :shock: :D
You do not have the required permissions to view the files attached to this post.
Orin

Smile today; tomorrow's another day!

DL MARTIN

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by DL MARTIN » Thu Jan 28, 2021 4:40 pm

When moon rocks were brought to Earth mention was made as to their geological age. Indeed the moon, itself, is referred as being billions of years old. Yet a galaxy is referred to as being so many light years away with no mention of the fact that what we are seeing is similarly aged. Why are we not constrained to account for the intervening time when the galaxy emitted the light we see at present. Or does the galaxy cease evolving in the eyes of astronomers. That seems out of the Dark Ages.

User avatar
johnnydeep
Commander
Posts: 949
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by johnnydeep » Thu Jan 28, 2021 6:04 pm

DL MARTIN wrote:
Thu Jan 28, 2021 4:40 pm
When moon rocks were brought to Earth mention was made as to their geological age. Indeed the moon, itself, is referred as being billions of years old. Yet a galaxy is referred to as being so many light years away with no mention of the fact that what we are seeing is similarly aged. Why are we not constrained to account for the intervening time when the galaxy emitted the light we see at present. Or does the galaxy cease evolving in the eyes of astronomers. That seems out of the Dark Ages.
Not quite sure what you're getting at, but we see galaxies as they were X years ago, where X is their distance in light years. We simply have no information on what has happened to them since then, though we can make projections based on velocities, and theories of galaxy evolution.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

User avatar
johnnydeep
Commander
Posts: 949
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by johnnydeep » Thu Jan 28, 2021 6:05 pm

APOD Robot wrote:
Thu Jan 28, 2021 5:05 am
Image Messier 66 Close Up

Explanation: Big, beautiful spiral galaxy Messier 66 lies a mere 35 million light-years away. The gorgeous island universe is about 100 thousand light-years across, similar in size to the Milky Way. This reprocessed Hubble Space Telescope close-up view spans a region about 30,000 light-years wide around the galactic core. It shows the galaxy's disk dramatically inclined to our line-of-sight. Surrounding its bright core, the likely home of a supermassive black hole, obscuring dust lanes and young, blue star clusters sweep along spiral arms dotted with the tell-tale glow of pinksh star forming regions. Messier 66, also known as NGC 3627, is the brightest of the three galaxies in the gravitationaly interacting Leo Triplet.
FYI - the first link is broken. It shows as "https://apod.nasa.gov/apod/://www.nasa. ... messier-66", but was probably meant to be https://www.nasa.gov/feature/goddard/2017/messier-66
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

DL MARTIN

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by DL MARTIN » Thu Jan 28, 2021 8:29 pm

Thanks for the clarification on the limit of knowing what happens in the intervening time from transmission to reception. What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.

User avatar
johnnydeep
Commander
Posts: 949
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by johnnydeep » Thu Jan 28, 2021 8:38 pm

DL MARTIN wrote:
Thu Jan 28, 2021 8:29 pm
Thanks for the clarification on the limit of knowing what happens in the intervening time from transmission to reception. What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.
I guess it's true that the concept "seeing afar is seeing old" is often taken for granted. But since there's no way to know what has actually happened to a far-old object since its light got to us, we don't have much of a choice. Though, as I said, often predictions of likely present or future activities can be meaningfully done, like the prediction that our sun will eventually swell to a red giant, or that Andromeda will eventually collide with The Milky Way.

I'm curious what Chris Peterson (or anyone else!) has to say.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Thu Jan 28, 2021 9:28 pm

DL MARTIN wrote:
Thu Jan 28, 2021 8:29 pm
Thanks for the clarification on the limit of knowing what happens in the intervening time from transmission to reception. What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.
Light moves unimaginably fast. Yet compared with the vastness of space, light seems to move slowly. And human lives are terribly brief.

We can't know of events whose signals, moving at the speed of light, have not yet reached us.

What can we do about it?

Are you implying that we shouldn't talk about the signals that have reached us, and the events and physical objects whose nature we can deduce from those signals?

Ann
Color Commentator

User avatar
Chris Peterson
Abominable Snowman
Posts: 16232
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Chris Peterson » Fri Jan 29, 2021 2:34 am

DL MARTIN wrote:
Thu Jan 28, 2021 8:29 pm
Thanks for the clarification on the limit of knowing what happens in the intervening time from transmission to reception. What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.
Because it is irrelevant. Indeed, the framework of special relativity is based on the idea that an event occurs when it is observed (technically, observable). We genuinely see the galaxy as it is, in almost every way that matters. There is no meaningful "now" that extends to the entire universe. Every location has its own "now".
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Fri Jan 29, 2021 6:52 am

What you disregard, DL MARTIN, is that time and space are connected. We can't break free of our own spacetime to find information about something that is not located in our own spacetime.


When I was 15 years old, I grabbed my parents' binoculars to go outside and have a look at Andromeda. It was incredibly powerful to see the pale yellow fuzzy spot and realize that I was looking at millions and possibly billions of stars at a glance. I felt convinced that there were habitable planets in that fuzzy spot, and in short, I had an overwhelmingly strong sense that I was "looking at aliens".

I started fantasizing that these aliens were not so different from myself. I imagined that there was another teenager in there on a planet in Andromeda, probably a girl, and maybe she was looking at us with her binoculars just like I was looking at her. I wanted to wave at her.

Years later I reviewed the possibility of "waving" - that is, sending a signal - to anyone inside Andromeda who might be looking our way. But if it was even possible to send such a signal, I realized that it would take two million years for it to reach any intelligent beings in Andromeda. And then, if the intelligent Andromedans decided that they wanted to send a signal back to us, it would take another two million years for that signal to reach us.


In short, if we were to send a signal to Andromeda, it would take four million years before we could even hope of getting an answer.

And if we - whoever "we" would be after four million years - actually got an answer from Andromeda, it still wouldn't tell us what Andromeda is like "now" (in what at that time would be our "now"). Because the answer from Andromeda would still be "two million years late".

We exist in another time frame than Andromeda. We can't know of each other's "now".

It is meaningless to ask what Andromeda is "now", and even more meaningless to ask what M66 is "now". Because there is no universal "now" in space, only all these separate locations in spacetime.

Ann
Color Commentator

User avatar
johnnydeep
Commander
Posts: 949
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by johnnydeep » Fri Jan 29, 2021 3:11 pm

Chris Peterson wrote:
Fri Jan 29, 2021 2:34 am
DL MARTIN wrote:
Thu Jan 28, 2021 8:29 pm
Thanks for the clarification on the limit of knowing what happens in the intervening time from transmission to reception. What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.
Because it is irrelevant. Indeed, the framework of special relativity is based on the idea that an event occurs when it is observed (technically, observable). We genuinely see the galaxy as it is, in almost every way that matters. There is no meaningful "now" that extends to the entire universe. Every location has its own "now".
I like to think I believe in relativity, but I still have a problem with this idea. Consider a star that we see in our "now" that appears to be still happily fusing elements to produce light. Now consider that in the star's "now", it has gone supernova. Naively, to say that the star still exists (to us), and that it no longer exists (from its perspective) are incompatible concepts. I guess I need to ponder this some more...
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

User avatar
Chris Peterson
Abominable Snowman
Posts: 16232
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Chris Peterson » Fri Jan 29, 2021 3:19 pm

johnnydeep wrote:
Fri Jan 29, 2021 3:11 pm
Chris Peterson wrote:
Fri Jan 29, 2021 2:34 am
DL MARTIN wrote:
Thu Jan 28, 2021 8:29 pm
Thanks for the clarification on the limit of knowing what happens in the intervening time from transmission to reception. What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.
Because it is irrelevant. Indeed, the framework of special relativity is based on the idea that an event occurs when it is observed (technically, observable). We genuinely see the galaxy as it is, in almost every way that matters. There is no meaningful "now" that extends to the entire universe. Every location has its own "now".
I like to think I believe in relativity, but I still have a problem with this idea. Consider a star that we see in our "now" that appears to be still happily fusing elements to produce light. Now consider that in the star's "now", it has gone supernova. Naively, to say that the star still exists (to us), and that it no longer exists (from its perspective) are incompatible concepts. I guess I need to ponder this some more...
But no claim is being made that it "still" exists... in great part because the concept of "still" is very hard to define.

In what way does it matter if it "still" exists? What matters is that we are seeing a star at a certain point in its evolution. What else has any relevance?
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
johnnydeep
Commander
Posts: 949
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by johnnydeep » Fri Jan 29, 2021 3:39 pm

Chris Peterson wrote:
Fri Jan 29, 2021 3:19 pm
johnnydeep wrote:
Fri Jan 29, 2021 3:11 pm
Chris Peterson wrote:
Fri Jan 29, 2021 2:34 am


Because it is irrelevant. Indeed, the framework of special relativity is based on the idea that an event occurs when it is observed (technically, observable). We genuinely see the galaxy as it is, in almost every way that matters. There is no meaningful "now" that extends to the entire universe. Every location has its own "now".
I like to think I believe in relativity, but I still have a problem with this idea. Consider a star that we see in our "now" that appears to be still happily fusing elements to produce light. Now consider that in the star's "now", it has gone supernova. Naively, to say that the star still exists (to us), and that it no longer exists (from its perspective) are incompatible concepts. I guess I need to ponder this some more...
But no claim is being made that it "still" exists... in great part because the concept of "still" is very hard to define.

In what way does it matter if it "still" exists? What matters is that we are seeing a star at a certain point in its evolution. What else has any relevance?
Hmm, so even existence is relative? Surely, an object's own space-time frame is the most accurate one? Well, that's what I WANT to say anyway. But I can see that there are frames a billion light years away in which the object does not exist YET, and also less far away frames where it still exists, as well as it's own frame where it has already stopped existing. True, though, "existence" is just a particular configuration of particles and forces. My classical physics upbringing is hard to shake.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

User avatar
Chris Peterson
Abominable Snowman
Posts: 16232
Joined: Wed Jan 31, 2007 11:13 pm
Location: Guffey, Colorado, USA

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Chris Peterson » Fri Jan 29, 2021 3:44 pm

johnnydeep wrote:
Fri Jan 29, 2021 3:39 pm
Chris Peterson wrote:
Fri Jan 29, 2021 3:19 pm
johnnydeep wrote:
Fri Jan 29, 2021 3:11 pm


I like to think I believe in relativity, but I still have a problem with this idea. Consider a star that we see in our "now" that appears to be still happily fusing elements to produce light. Now consider that in the star's "now", it has gone supernova. Naively, to say that the star still exists (to us), and that it no longer exists (from its perspective) are incompatible concepts. I guess I need to ponder this some more...
But no claim is being made that it "still" exists... in great part because the concept of "still" is very hard to define.

In what way does it matter if it "still" exists? What matters is that we are seeing a star at a certain point in its evolution. What else has any relevance?
Hmm, so even existence is relative? Surely, an object's own space-time frame is the most accurate one? Well, that's what I WANT to say anyway. But I can see that there are frames a billion light years away in which the object does not exist YET, and also less far away frames where it still exists, as well as it's own frame where it has already stopped existing. True, though, "existence" is just a particular configuration of particles and forces. My classical physics upbringing is hard to shake.
Existence isn't relative. What does "accurate" mean in this context? What matters besides the reality that we are seeing objects as they are at certain ages? If you watch an old film of a person speaking, do you complain because it fails to represent the person as they will be 20 years later, and 20 years in our own past?
Chris

*****************************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

User avatar
neufer
Vacationer at Tralfamadore
Posts: 18576
Joined: Mon Jan 21, 2008 1:57 pm
Location: Alexandria, Virginia

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by neufer » Fri Jan 29, 2021 9:33 pm

Chris Peterson wrote:
Fri Jan 29, 2021 2:34 am
DL MARTIN wrote:
Thu Jan 28, 2021 8:29 pm

What concerns me is that the idea that what we are perceiving is simply away rather than also ago seems to ignore change at the source. Its as if the Sun doesn't change during the intervening eight minutes of light travel. Yet we seem to deny this reality when referring to galaxies.
Because it is irrelevant. Indeed, the framework of special relativity is based on the idea that an event occurs when it is observed (technically, observable). We genuinely see the galaxy as it is, in almost every way that matters. There is no meaningful "now" that extends to the entire universe. Every location has its own "now".
In GENERAL relativity there is, indeed, a meaningful "now" that extends to the entire universe: "Now" is the time period when the Cosmic Microwave Background is at ~2.725 K (or roughly 13.8 billion years after the Big Bang).

However, we have no reason to believe that the set of galaxies within about 3 billion light years of us are at all unrepresentative of the galaxies which currently exist "now". Hence, the only real scientific purpose of knowing the distance to such "nearby" galaxies is:
  • 1) to determine the current expansion rate of the Universe
    2) to determine the size of the galaxy
    3) to determine the color of the galaxy.
https://en.wikipedia.org/wiki/Chronology_of_the_universe wrote:
<<The earliest stages of the universe's existence are estimated as taking place 13.8 billion years ago. After about 370,000 years, the universe finally becomes cool enough for neutral atoms to form ("recombination"), and as a result it also became transparent for the first time. The newly formed atoms—mainly hydrogen and helium with traces of lithium—quickly reach their lowest energy state (ground state) by releasing photons ("photon decoupling"), and these photons can still be detected today as the cosmic microwave background (CMB). This is currently the oldest observation we have of the universe.

After recombination and decoupling, the universe was transparent but the clouds of hydrogen only collapsed very slowly to form stars and galaxies, so there were no new sources of light. The only photons (electromagnetic radiation, or "light") in the universe were those released during decoupling (visible today as the cosmic microwave background) and 21 cm radio emissions occasionally emitted by hydrogen atoms. The decoupled photons would have filled the universe with a brilliant pale orange glow at first, gradually redshifting to non-visible wavelengths after about 3 million years, leaving it without visible light. This period is known as the cosmic Dark Ages.

Between about 10 and 17 million years the universe's average temperature was suitable for liquid water 273–373 K (0–100 °C) and there has been speculation whether rocky planets or indeed life could have arisen briefly, since statistically a tiny part of the universe could have had different conditions from the rest as a result of a very unlikely statistical fluctuation, and gained warmth from the universe as a whole.

At some point around 200 to 500 million years, the earliest generations of stars and galaxies form (exact timings are still being researched), and early large structures gradually emerge, drawn to the foam-like dark matter filaments which have already begun to draw together throughout the universe. The earliest generations of stars have not yet been observed astronomically. They may have been huge (100-300 solar masses) and non-metallic, with very short lifetimes compared to most stars we see today, so they commonly finish burning their hydrogen fuel and explode as highly energetic pair-instability supernovae after mere millions of years. Other theories suggest that they may have included small stars, some perhaps still burning today. In either case, these early generations of supernovae created most of the everyday elements we see around us today, and seeded the universe with them.

Galaxy clusters and superclusters emerge over time. At some point, high energy photons from the earliest stars, dwarf galaxies and perhaps quasars leads to a period of reionization that commences gradually between about 250-500 million years, is complete by about 700-900 million years, and diminishes by about 1 billion years (exact timings still being researched). The universe gradually transitioned into the universe we see around us today, and the Dark Ages only fully came to an end at about 1 billion years.

From 1 billion years, and for about 12.8 billion years, the universe has looked much as it does today. It will continue to appear very similar for many billions of years into the future. The thin disk of our galaxy began to form at about 5 billion years (8.8 Gya), and the Solar System formed at about 9.2 billion years (4.6 Gya), with the earliest traces of life on Earth emerging by about 10.3 billion years (3.5 Gya).

From about 9.8 billion years of cosmic time, the slowing expansion of space gradually begins to accelerate under the influence of dark energy, which may be a scalar field throughout our universe.>>
Art Neuendorffer

User avatar
johnnydeep
Commander
Posts: 949
Joined: Sun Feb 20, 2011 8:57 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by johnnydeep » Sat Jan 30, 2021 12:32 am

Chris Peterson wrote:
Fri Jan 29, 2021 3:44 pm
johnnydeep wrote:
Fri Jan 29, 2021 3:39 pm
Chris Peterson wrote:
Fri Jan 29, 2021 3:19 pm


But no claim is being made that it "still" exists... in great part because the concept of "still" is very hard to define.

In what way does it matter if it "still" exists? What matters is that we are seeing a star at a certain point in its evolution. What else has any relevance?
Hmm, so even existence is relative? Surely, an object's own space-time frame is the most accurate one? Well, that's what I WANT to say anyway. But I can see that there are frames a billion light years away in which the object does not exist YET, and also less far away frames where it still exists, as well as it's own frame where it has already stopped existing. True, though, "existence" is just a particular configuration of particles and forces. My classical physics upbringing is hard to shake.
Existence isn't relative. What does "accurate" mean in this context? What matters besides the reality that we are seeing objects as they are at certain ages? If you watch an old film of a person speaking, do you complain because it fails to represent the person as they will be 20 years later, and 20 years in our own past?
Thanks, Chris, for still more to think about. And to neufer for the idea that a true “now” can be defined by the temperature of the CMB, which will presumably be measured to be the same by everyone anywhere in the universe, and which will gradually decrease due to the expansion of space.
--
"To B̬̻̋̚o̞̮̚̚l̘̲̀᷾d̫͓᷅ͩḷ̯᷁ͮȳ͙᷊͠ Go......Beyond The F͇̤i̙̖e̤̟l̡͓d͈̹s̙͚ We Know."

VictorBorun
Science Officer
Posts: 361
Joined: Fri Oct 16, 2020 10:25 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by VictorBorun » Sat Jan 30, 2021 6:05 am

They say "The isophotal axis ratio is 0.32", so I compressed the pic to get a face-on view.
Now even clearer is the dust visibility trick played by the shining bulge: the dusty lanes in front of the backlight are strikingly brown and the dusty lanes on the othes side are ghostly pale.

VictorBorun
Science Officer
Posts: 361
Joined: Fri Oct 16, 2020 10:25 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by VictorBorun » Sat Jan 30, 2021 6:31 am

Ann wrote:
Thu Jan 28, 2021 10:46 am
M66 has a "squashed S-shape that is unmistakable.
But M66 also has a broad "blue flow" of bright stars just below the dust lane framing the yellow bar.
the big S of the arms after 0.32 compressing is asymmetric.
Even more asymmetric M66 looks with its Great Blue Spot.

And overall shape is an ellipsis rather than a disk. Can it be so distorted with tidal forces?

Or could it be that 0.32 compressing should be applied in another direction altogether? Than the nice picture in my previous comment is irrelevant and the dust disk in the bulge with its dust visibility halves is a freak :(
Last edited by VictorBorun on Sat Jan 30, 2021 8:51 am, edited 1 time in total.

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Sat Jan 30, 2021 7:27 am

VictorBorun wrote:
Sat Jan 30, 2021 6:31 am
Ann wrote:
Thu Jan 28, 2021 10:46 am
M66 has a "squashed S-shape that is unmistakable.
But M66 also has a broad "blue flow" of bright stars just below the dust lane framing the yellow bar.
the big S of the arms after 0.32 compressing is asymmetric.
Even more asymmetric M66 looks with its Great Blue Spot.

And overall shape is an ellipsis rather than a disk. Can it be so distorted with tidal forces?
In view of the fact that M66 is in a "tidal dance" with M65 and NGC 2836, yes, it is certainly distorted by tidal forces.

Few galaxies are strikingly symmetrical. One of the most symmetrical galaxies I know of is NGC 2857.

NGC 2857 is a grand design galaxy, which is to say that it has two long main arms. The arms are so long that they each wind more than a full turn around the nucleus, which is rare.

NGC 2857 is forming stars along the length of its arms at what looks like a moderate pace. In this way, it does not create massive individual "hot spots" that might destroy its symmetry from within.

It also appears to be relatively lonely in space. That way, it isn't affected by strong tidal forces from without. Interestingly, and unlike M66, it doesn't have a bright outer disk of old stars, which might have pulled on the spiral arms from without.

NGC 2857 made it into Halton Arp's Atlas of Peculiar Galaxies, possibly because it is so symmetrical.

However, as for M66, remember that it is inclined to our line of sight. It would certainly not be perfectly symmetrically shaped if we could see it face on, but it might be a bit less irregular than it appears to be from this "viewing angle".

Ann
Color Commentator

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Sat Jan 30, 2021 7:52 am

neufer wrote:
Fri Jan 29, 2021 9:33 pm

In GENERAL relativity there is, indeed, a meaningful "now" that extends to the entire universe: "Now" is the time period when the Cosmic Microwave Background is at ~2.725 K (or roughly 13.8 billion years after the Big Bang).
Very interesting, Art. Tell me, though. The photons that we receive from M66 and catch with our telescopes most certainly inhabit our "now" and our CMB temperature (or they did when our telescopes saw them).

What about a position some 35 million light-years away? Surely the CMB temperature can't change that much over 35 million light-years?

Does that mean that M66 is part of our "now"? Not because we receive photons from M66, because we receive photons from galaxies billions of light-years away, but because its CMB temperature is the same as ours?

Or isn't it?

Ann
Color Commentator

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Sat Jan 30, 2021 10:41 am

Instead of messing up my post about NGC 2857, I decided to make another post where I compare this highly symmetrical spiral galaxy with a spiral galaxy that is not symmetrical at all.

As you can see, M99 appears to be tugged at by strong tidal forces, and it also experiences high levels of star formation, which in itself is an impediment to a symmetrical shape.
Wikipedia wrote:

This galaxy has a morphological classification of SA(s)c, indicating a pure spiral shape with loosely wound arms. It has a peculiar shape with one normal looking arm and an extended arm that is less tightly wound.
...
A bridge of neutral hydrogen gas links NGC 4254 with VIRGOHI21, an HI region and a possible dark galaxy. The gravity from the latter may have distorted M99 and drawn out the gas bridge, as the two galaxy-sized objects may have had a close encounter before they went their separate ways. However, VIRGOHI21 may instead be tidal debris from an interaction with the lenticular galaxy NGC 4262 some 280 million years ago.
...
While not classified as a starburst galaxy, M99 has a star formation activity three times larger than other galaxies of similar Hubble type that may have been triggered by the encounter. M99 is likely entering the Virgo Cluster for the first time and is located at the periphery of the cluster at a projected separation of 3.7°, or around one megaparsec, from the cluster center at Messier 87. The galaxy is undergoing ram-pressure stripping as it moves through the intracluster medium.
As for NGC 2857, it would seem to be a low surface brightness galaxy, which indicates that its rate of star formation is low, too. But if so, its rate of star formation has probably not been much greater in the past, since the galaxy appears to lack a bright old yellow population, except in its small nuclear region.

Ann
Color Commentator

VictorBorun
Science Officer
Posts: 361
Joined: Fri Oct 16, 2020 10:25 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by VictorBorun » Sat Jan 30, 2021 1:51 pm

If M99 is a cluster breaker distorted by the headwind of the intergalactic media in the Virgo Cluster,
why should M66 be distorted by the other galaxies of Leo triplet? Can M66 be a crusher too?

It has its blue in plenty. Even a Great Blue Pocket.

User avatar
Ann
4725 Å
Posts: 11656
Joined: Sat May 29, 2010 5:33 am

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by Ann » Sat Jan 30, 2021 2:21 pm

VictorBorun wrote:
Sat Jan 30, 2021 1:51 pm
If M99 is a cluster breaker distorted by the headwind of the intergalactic media in the Virgo Cluster,
why should M66 be distorted by the other galaxies of Leo triplet? Can M66 be a crusher too?

It has its blue in plenty. Even a Great Blue Pocket.
I don't think that M66 is a crusher, but it is definitely affected by tidal forces caused by M65 and NGC 3628.

M65 (at far right in the picture at right) seems unaffected by the tidal forces of its neighbors. Yes, but look at NGC 3628 (above center). Look at how puffed-up the ends of its disk are! That's not what edge-on disk galaxies normally look like. And look at that magnificent tidal tail stretching for, probably, more than 100,000 light-years to the "left" of the main body of the galaxy!

There are tidal forces at work in the region of the Leo Triplet all right!

Ann
Color Commentator

VictorBorun
Science Officer
Posts: 361
Joined: Fri Oct 16, 2020 10:25 pm

Re: APOD: Messier 66 Close Up (2021 Jan 28)

Post by VictorBorun » Sat Jan 30, 2021 2:45 pm

ok, got it.

By the way, when a galaxy rams into a cluster and gets shiny and blue, is the blue from blue giants and supergiants formation?
Can it be directly the galaxy gas disk hitting the cluster gas?
Thermal light is blue when it is very hot. Not 6000°K like the Sun but say 20,000°K.
At 300° thermal speed of molecules is 400 m/s (N2) or 1200 m/s (He). I guess it's 1700 m/s (H2) or 2400 m/s (H).
So at 20,000°K it's 70 times the energy or 8 times the speed, 20,000 km/s
OK, I quit. Ramming into a cluster at 3000 km/s is done, at 20,000 km/s is not.

Update. Oh no, my math is all wrong. 8 times the speed of 2400 m/s (one-atom H) is only 20 km/s, a tiny figure compared to a rammer's 3000 km/s.
So the kinetic energy for blue, UV and Xray is there. Mechanics to translate kinetic energy to light is another thing.
Last edited by VictorBorun on Sat Jan 30, 2021 5:56 pm, edited 1 time in total.