APOD: M64: The Evil Eye Galaxy (2021 Mar 29)

[APOD Robot]

M64: The Evil Eye Galaxy

Explanation: Who knows what evil lurks in the eyes of galaxies? The Hubble knows -- or in the case of spiral galaxy M64 -- is helping to find out. Messier 64, also known as the Evil Eye or Sleeping Beauty Galaxy, may seem to have evil in its eye because all of its stars rotate in the same direction as the interstellar gas in the galaxy's central region, but in the opposite direction in the outer regions. Captured here in great detail by the Earth-orbiting Hubble Space Telescope, enormous dust clouds obscure the near-side of M64's central region, which are laced with the telltale reddish glow of hydrogen associated with star formation. M64 lies about 17 million light years away, meaning that the light we see from it today left when the last common ancestor between humans and chimpanzees roamed the Earth. The dusty eye and bizarre rotation are likely the result of a billion-year-old merger of two different galaxies.

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[RocketRon]

because all of its stars rotate in the same direction as the interstellar gas in the galaxy's central region, but in the opposite direction in the outer regions.

I'm curious - how was this determined ?
In a few short years of observations, would the relative shift in positions have been observable in photographs.

Or do other factors come into play here.

[Ann]

because all of its stars rotate in the same direction as the interstellar gas in the galaxy's central region, but in the opposite direction in the outer regions.

I'm curious - how was this determined ?
In a few short years of observations, would the relative shift in positions have been observable in photographs.

Or do other factors come into play here.

NGC 4622, a spiral galaxy whose inner and outer arms rotate in different directions. NASA and The Hubble Heritage Team (STScI/AURA).

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NGC 4622 annotated. NASA and The Hubble Heritage Team (STScI/AURA)

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NGC 4622 is a prime example of a galaxy whose inner and outer arms rotate in different directions.

M64. Photo: Andrea Tamanti.

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M64. Photo: Andrea Tamanti.

I think I can see something similar in M64. The inner and outer cyan-colored arrows show what looks to me like the "direction of the arms". The yellow cross is where I think you find the approximate point of "bifurcation", where the rotation splits from one direction to the other.

I'm sure there are nice mathematical ways of measuring the rotation in various parts of M64. You'll have to ask the math people about that. (Yeah, I think I remember that there is something about the Doppler shift...)

Ann

Click to view full size image

EDIT: We expect galaxy arms to be trailing, even if there are a very few exceptions, like in NGC 4622. That means that if the arms of M64 are trailing, the arrows should point the other way than they do in my annotation. Imagine that the arms are "tails", trailing behind as the galaxy rotates the way a toy on a leash might trail behind a child.

[Gert-Jan]

Astronomically speaking it isn't very important, but the last common ancestor of chimpanzees and humans probably lived between 5 and 7 million years ago. 17 million years ago was more or less the time when the great apes and the gibbons parted ways.

The rotation of stars around galaxies can (often, depending on the orientation) be determined spectroscopically.
If a star is moving towards us, then its light is made a little bit more blue, if he is moving away, then it becomes a little bit more red.
Thus, by carefully studying the emission and absorption lines in the spectra of the stars, it is possible to determine the rotation of a far away galaxy. Typically, on one half of it the stars will be moving towards us (blue) and on the other side they will be moving away. Precisely what one sees in a free spinning wheel. In this case, this simple scheme isn't followed; instead, the centre of the galaxy is rotating in one direction and the outer regions in the other.
Now, this does not work if we look precisely down (or up) at a galaxy. In that case, there won't be any effective motion of the stars to be observed, and consequently we can't tell how it is rotating.

[luciham20]

Thanks for the information on this. I really enjoy the information. google

[De58te]

Nitpicking correction. In the Apod robot's link "last common ancestor" it states that, 'Homininae ancestors speciate from the ancestors of the orangutan between c. 18 to 14 Ma.' And a little further down, 'Hominini: The latest common ancestor of humans and chimpanzees is estimated to have lived between roughly 10 to 5 million years ago.' So technically speaking that 17 million years ago the true hominid apes split from the orangutan. What would become the human species wasn't separated from the chimps 17 million years ago.

[Ann]

M64, the Black (or Evil) Eye galaxy. Image Credit: ESA/Hubble & NASA & the PHANGS-HST Team; Acknowledgement: Judy Schmidt

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This is how I would annotate the picture of M64:

1) A foreground Milky Way star. Note the diffraction spikes.

2) A compact globular cluster belonging to M64. The object is very round and white and lacks diffraction spikes due to the fact that it is not a point source (and also due to the fact that the resolution of the image is not high enough to reveal the faint diffraction spikes that are in fact there).

3) By far the largest and brightest association of young blue stars in M64.

4) A background galaxy.

5) A part of the disk that almost completely lacks blue stars. Its stellar population seems to consist of old red stars only. It is likely that most of the disk of M64 is like that.

6) A stream of blue stars that were formed in the dark central dust cloud. Some of these blue stars are now being carried into the surrounding disk by the rotation of the galaxy.

Ann

[Ann]

Let's compare M64 with a grand design spiral galaxy, M100.

M64:

1) Bright yellow core.

2) Very dark and broad inner dust lane with low levels of star formation.

3) A mostly featureless disk.


M100:

1) Bright yellow core.

2) Brilliant inner ring of star formation.

3) A well-defined dust lane leading from the core into the disk.

4) The dust lane from the core connects to the dust lane that defines one of the two long arms of M100. Star formation is taking place in along this arm.

Ann

[orin stepanek]

Looks more like a black eye to me; maybe got a licking from some thug!
All in all a nice looking spiral!

[XgeoX]

meaning that the light we see from it today left when the last common ancestor between humans and chimpanzees roamed the Earth.

Not true, the last common ancestor of human and chimpanzees roamed the earth until only four years ago...

George “The Animal’ Steele!
RIP Animal

Eric

[Cousin Ricky]

I haven’t seen Geck a lot here lately, but I am noticing her images around the Web.

[johnnydeep]

Ok, I'll bite: Evil Eye I can see, but what about galaxy this brings to mind Sleeping Beauty?

[Ann]

I can't stop comparing M64 with other galaxies, so here is my next one:

The central part of M64, which displays a very thick dust lane and some star formation. Faint streamers of blue stars flow from the central site of star formation into the disk, which is otherwise all 'red and dead'. Image Credit: ESA/Hubble & NASA & the PHANGS-HST Team; Acknowledgement: Judy Schmidt.

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The central part of NGC 4314, which displays an inner ring of star formation. Faint streamers of blue stars flow from the starforming ring into the surrounding disk and spiral arms, which are otherwise all 'red and dead'. Credit: G. Fritz Benedict, Andrew Howell, Inger Jorgensen, David Chapell (University of Texas), Jeffery Kenney (Yale University), and Beverly J. Smith (CASA, University of Colorado), and NASA.

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M64, the Black Eye Galaxy, in its entirety. It is a disk galaxy with an underdeveloped spiral shape. It lacks star formation and young stars everywhere except near its core. Photo: Andrea Tamanti.

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NGC 4314 in its entirety. It is an elegant barred spiral galaxy that is completely devoid of star formation and young stars everywhere except near its core. Credit: G. Fritz Benedict, Andrew Howell, Inger Jorgensen, David Chapell (University of Texas), Jeffery Kenney (Yale University), and Beverly J. Smith (CASA, University of Colorado), and NASA.

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So M64 and NGC 4314 are two morphologically quite different galaxies, but what they have in common is that they contain no major dust lanes, star formation or young stars anywhere except in a small area near their cores.

Ann

[starsurfer]

I thought this was the Black Eye Galaxy?

[XgeoX]

M64_Hubble_960.jpg

Looks more like a black eye to me; maybe got a licking from some thug!
All in all a nice looking spiral!

The Cambridge Photographic Atlas of Galaxies lists it as “The Black Eye” galaxy so they agree with you!

Eric

[ems57fcva]

Nitpicking correction. In the Apod robot's link "last common ancestor" it states that, 'Homininae ancestors speciate from the ancestors of the orangutan between c. 18 to 14 Ma.' And a little further down, 'Hominini: The latest common ancestor of humans and chimpanzees is estimated to have lived between roughly 10 to 5 million years ago.' So technically speaking that 17 million years ago the true hominid apes split from the orangutan. What would become the human species wasn't separated from the chimps 17 million years ago.

I am also wondering where the 17 Ma date for the Homo-Pan (human-chimapanzee) split came from. I for one agree with that dating, but that view that is not common in the scientific community. The common view is actually 5-10 Ma for the human-chimpanzee LCA date, with the biological clock supporting a 5-7 Ma LCA date. I personally feel that the calibration of the biological clock that produces that conclusion is off by a factor of ~3, hence my support for 17 Ma as the date.

I will not go into further details on my thinking. Maybe the 17 Ma date will turn out to be correct and maybe not. The important thing is that the light from M64 that we are seeing now started towards us long before H. sapiens came to be.

[bystander]

I thought this was the Black Eye Galaxy?

... Messier 64, also known as the Evil Eye or Sleeping Beauty Galaxy, ...

The Black Eye Galaxy (also called Evil Eye Galaxy and designated Messier 64, M64, or NGC 4826) ...