APOD: Messier 51 in 255 Hours (2023 Aug 11)

[APOD Robot]

Messier 51 in 255 Hours

Explanation: An intriguing pair of interacting galaxies, M51 is the 51st entry in Charles Messier's famous catalog. Perhaps the original spiral nebula, the large galaxy with whirlpool-like spiral structure seen nearly face-on is also cataloged as NGC 5194. Its spiral arms and dust lanes sweep in front of a companion galaxy (right), NGC 5195. Some 31 million light-years distant, within the boundaries of the well-trained constellation Canes Venatici, M51 looks faint and fuzzy to the eye in direct telescopic views. But this remarkably deep image shows off stunning details of the galaxy pair's striking colors and extensive tidal debris. A collaboration of astro-imagers using telescopes on planet Earth combined over 10 days of exposure time to create this definitive galaxy portrait of M51. The image includes 118 hours of narrowband data that also reveals a vast glowing cloud of reddish ionized hydrogen gas discovered in the M51 system.

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[Ann]

Messier 51 in 255 Hours. Credit: The Deep Sky Collective.

What a great image! Above all, it's an amazing portrait of the huge "sheets" of low-mass stars (beige in color) that have been driven out of both galaxies, M51 and NGC 5195, due to tidal forces as a consequence of the interaction between these galaxies.

I also love the red patch of ionized hydrogen to the right!

Superb! The Deep Sky Collective has indeed shown us M51 in a new light!

Ann

[rstevenson]

This is an extraordinary effort by a large group of Astro-imagers. I am intrigued by a few black blobs in the middle right of the image, below the blue streak, circled in my detail screen grab here…

In images within the Milky Way such black blobs are usually a dense cloud of gas and dust, almost certain to become one or more stars eventually. If these blobs in M51 are similar they must be immense. Does anyone know what they are for sure? Conceivably they are actually within our Milky Way, but in the comments under the image on the group’s main image page someone says that there are few such local blobs or nebulae in the direction of M51. They weren’t specifically referring to these black blobs though.

Rob

[the_astronomy_enthusiast]

This is an extraordinary effort by a large group of Astro-imagers. I am intrigued by a few black blobs in the middle right of the image, below the blue streak, circled in my detail screen grab here…
IMG_0811.jpeg
In images within the Milky Way such black blobs are usually a dense cloud of gas and dust, almost certain to become one or more stars eventually. If these blobs in M51 are similar they must be immense. Does anyone know what they are for sure? Conceivably they are actually within our Milky Way, but in the comments under the image on the group’s main image page someone says that there are few such local blobs or nebulae in the direction of M51. They weren’t specifically referring to these black blobs though.

Rob

Hi Rob! When I processed this image, I did a lot of referring to the Hubble version of this. After so careful comparison, I think we can conclude that those dark blobs are actually distorted and shredded dust lanes from NGC 5915.

[rstevenson]

This is an extraordinary effort by a large group of Astro-imagers. I am intrigued by a few black blobs in the middle right of the image, below the blue streak, circled in my detail screen grab here…
IMG_0811.jpeg
In images within the Milky Way such black blobs are usually a dense cloud of gas and dust, almost certain to become one or more stars eventually. If these blobs in M51 are similar they must be immense. Does anyone know what they are for sure? Conceivably they are actually within our Milky Way, but in the comments under the image on the group’s main image page someone says that there are few such local blobs or nebulae in the direction of M51. They weren’t specifically referring to these black blobs though.

Rob

Hi Rob! When I processed this image, I did a lot of referring to the Hubble version of this. After so careful comparison, I think we can conclude that those dark blobs are actually distorted and shredded dust lanes from NGC 5915.

Thanks! Fantastic work by all the members of the collective.

Rob

[De58te]

I would like to know what causes those large patches of baby blue stars which aren't co-mingled with white or red stars? You can see an example at 1 to 2 o'clock in Rob's close up screen grab. And directly below that at 3 o'clock are a patch of all red stars. Is that due from the collision and the red stars due to red shift are flung away from our direction and the blue stars are moving towards us?

[the_astronomy_enthusiast]

I would like to know what causes those large patches of baby blue stars which aren't co-mingled with white or red stars? You can see an example at 1 to 2 o'clock in Rob's close up screen grab. And directly below that at 3 o'clock are a patch of all red stars. Is that due from the collision and the red stars due to red shift are flung away from our direction and the blue stars are moving towards us?

Assuming we are talking about the same thing, the blue stream (1) is a stellar stream caused by the interaction between the galaxies, and the red stream (2) is an outflowing of ionized hydrogen gas that contributes to the cliffs on the right side of the image.

[Christian G.]

Superb and fantastic have already been used, I'll add awesome and breathtaking image!

[Roy]

Superb and fantastic have already been used, I'll add awesome and breathtaking image!

And a complex overall environment made visible! I don’t think the old narratives of “a large galaxy eating a small one” and “tidal debris” will suffice. Are they fissioning? What about the knot of dim stars, just about on a line of the two galaxies further out?

[Ann]

Thanks for the interesting discussion! I just noticed the following:

Is that red thing a jet of ionized gas emanating from the core of NGC 5195? And if it is a jet, does it end in a bow shock?

And what is that gray cluster-like thing in the "beige arm" of M51? Could it be an old cluster of some sort, or maybe, more likely, an non-starforming faint satellite galaxy?

Ann

[AVAO]

Thanks for the interesting discussion! I just noticed the following:

APOD 11 August 2023 detail.png

APOD 11 August 2023 detail annotated.png

Is that red thing a jet of ionized gas emanating from the core of NGC 5195? And if it is a jet, does it end in a bow shock?

And what is that gray cluster-like thing in the "beige arm" of M51? Could it be an old cluster of some sort, or maybe, more likely, an non-starforming faint satellite galaxy?

Ann

ThanX Ann

First of all. What a great APOD!
Congratulations also to this great team, a clear case for the APOD Hall of Fame.

I think the case is really complex here. If you look at the environment in the radio wavelenght, however, a lot becomes clearer. But I don't think that the red arm fragment to the left of the small galaxy NGC 5195 represents a bow shock wave.
I could rather imagine that this is in a way ionized ("illuminated") by the core of NGC 5195.

In the radio frequency range you can see that the red arm fragment is part of a larger and strongly meandering arm (white lines) that forms a loop in the lower right field.

Click to view full size image

Original Radiowave Data (blue & red): NRAO (National Radio Astronomy Observatory)
White contours: H I from 34′′ resolution VLA interferometry map of Rots et al. (1990)

Click to view full size image

Original Infill Data NASA / ESA (SST/HST)

[orin stepanek]

Canes Venatici,would not open
! think; IMHO; M51 looks like an ear!

[Avalon]

My eye was drawn to the bright, little gem of a galaxy at the lower left corner. I'd love to see sharper images of that one, if we could only get closer.

Are galaxies always tugging on each other gravitationally even from tremendous distances, or do they have to be within a certain proximity of each other to get the collision course started?

[Chris Peterson]

My eye was drawn to the bright, little gem of a galaxy at the lower left corner. I'd love to see sharper images of that one, if we could only get closer.

Are galaxies always tugging on each other gravitationally even from tremendous distances, or do they have to be within a certain proximity of each other to get the collision course started?

Everything tugs on everything, regardless of distance (as long as they lie in each other's observably universe). But between galaxies, we only see collisions where galaxies are close enough together that they are gravitationally bound, in orbit around each other. The little galaxy in this image will never merge with M51. The two have relative speeds much higher than escape velocity.

[Ann]

My eye was drawn to the bright, little gem of a galaxy at the lower left corner. I'd love to see sharper images of that one, if we could only get closer.

Yes, mine too. The galaxy in question is IC 4263. I googled it, but I could find no sharp pictures of it. These two pictures are, unfortunately, the best I could find:

IC 4263. Image credit: SDSS/Donald Pelletier.

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IC 4263. Image credit: NED/SDSS

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So we have two SDSS images, one somewhat yellowish, the other blue. So what color is IC 4263 really? NASA's now-defunct ultraviolet telescope GALEX can help us:

IC 4263. Image credit: NASA/GALEX.

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I think the overall GALEX color of IC 4263 resembles that of the GALEX color of NGC 5705, Let's compare it with the SDSS picture of NGC 5705 while we are at it:

NGC 5705. Image credit: NASA/GALEX.

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NGC 5705. Image credit: SDSS.

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Let's get back to IC 4263. There is a Wikipedia entry on it - in French! My French is somewhere between terrible and non-existent! Anyway, this is what I managed to figure out from the French info:

The distance to IC 4263 is 139 million light-years (give or take, I would say!). Its redshift apparently suggests a distance of 131 million light-years. Same difference!

Although, when I checked my software, the redshift of IC 4263 appears to be much the same as the redshift of M51 itself, whose distance is circa 30 million light-years... Really!!)

The Hubble type of IC 4363 is most likely either SB(s)d or SBcd. The capital B means that IC 4263 is barred, the (s) means that there is no ring, and the Sd or Scd means that IC 4263 is a spiral galaxy with loosely wound arms and a patchy, broken structure.

M108, type SB(s)cd. Image credit: NOIRLab/NSF/AURA.

---

Once again, back to IC 4263. According to French Wikipedia, it is a low surface brightness galaxy. This could be true, in view of the fact that the center of the galaxy, while yellow, is not bright. The lack of a bright yellow center suggests not only that the galaxy has a low surface brightness, but also that it is fairly low in mass.

French Wikipedia also says that the V magnitude of IC 4263 is 14.5. This makes it six magnitudes fainter than M51, whose V magnitude (according to English Wikipedia) is 8.4. The (uncertain) distance to M51 is either 23 or 31 million light-years, according to Wikipedia.

And I guess that is what I can say about IC 4263!

Ann

[johnnydeep]

My eye was drawn to the bright, little gem of a galaxy at the lower left corner. I'd love to see sharper images of that one, if we could only get closer.

Are galaxies always tugging on each other gravitationally even from tremendous distances, or do they have to be within a certain proximity of each other to get the collision course started?

Everything tugs on everything, regardless of distance (as long as they lie in each other's observably universe). But between galaxies, we only see collisions where galaxies are close enough together that they are gravitationally bound, in orbit around each other. The little galaxy in this image will never merge with M51. The two have relative speeds much higher than escape velocity.

Let me just add some further explanation of an answer to the OP's question about "tugging". The force of gravity is governed by Newton's Law of Universal Gravitation. From https://en.wikipedia.org/wiki/Newton%27 ... odern_form

So, no matter how far apart two bodies - or galaxies - are, the gravitational force between them will never be zero. The division by r² will make the force as close to zero as you want, but it will always be positive. However, when more than two objects are involved - which is the actual case in reality everywhere! - one body will always end up having the greatest force on another body, and "win" the tug of war. And then there is the added complication of all things being in motion with respect to others, which can prevent collisions (e.g. via orbits, as Chris was explaining) even though the force of gravity is unaffected.

I tried to find out if relativity modifies the standard law shown above, but google wasn't providing an answer. Surely though, near the surface of neutron stars, or near the event horizons of black holes, or when objects are moving at relativistic speeds, the equation for the law has to change, right? (I'm expecting terms like 1/√(1-(v²/c²) to make an appearance.)

Oh, and then there is dark energy (an apparent universal repulsive force!) which will also have to alter Newton's standard equation. Right?

[Chris Peterson]

My eye was drawn to the bright, little gem of a galaxy at the lower left corner. I'd love to see sharper images of that one, if we could only get closer.

Are galaxies always tugging on each other gravitationally even from tremendous distances, or do they have to be within a certain proximity of each other to get the collision course started?

Everything tugs on everything, regardless of distance (as long as they lie in each other's observably universe). But between galaxies, we only see collisions where galaxies are close enough together that they are gravitationally bound, in orbit around each other. The little galaxy in this image will never merge with M51. The two have relative speeds much higher than escape velocity.

Let me just add some further explanation of an answer to the OP's question about "tugging". The force of gravity is governed by Newton's Law of Universal Gravitation. From https://en.wikipedia.org/wiki/Newton%27 ... odern_form


newtons law of universal gravitation wikipedia.jpg


So, no matter how far apart two bodies - or galaxies - are, the gravitational force between them will never be zero. The division by r² will make the force as close to zero as you want, but it will always be positive. However, when more than two objects are involved - which is the actual case in reality everywhere! - one body will always end up having the greatest force on another body, and "win" the tug of war. And then there is the added complication of all things being in motion with respect to others, which can prevent collisions (e.g. via orbits, as Chris was explaining) even though the force of gravity is unaffected.

I tried to find out if relativity modifies the standard law shown above, but google wasn't providing an answer. Surely though, near the surface of neutron stars, or near the event horizons of black holes, or when objects are moving at relativistic speeds, the equation for the law has to change, right? (I'm expecting terms like 1/√(1-(v²/c²) to make an appearance.)

Oh, and then there is dark energy (an apparent universal repulsive force!) which will also have to alter Newton's standard equation. Right?

The gravitational force between two bodies is exactly the same on both of them, no matter their individual masses. A grain of sand feels the same force from the Earth as the Earth feels from the grain of sand. Adding more bodies doesn't change this.

[johnnydeep]

Everything tugs on everything, regardless of distance (as long as they lie in each other's observably universe). But between galaxies, we only see collisions where galaxies are close enough together that they are gravitationally bound, in orbit around each other. The little galaxy in this image will never merge with M51. The two have relative speeds much higher than escape velocity.

Let me just add some further explanation of an answer to the OP's question about "tugging". The force of gravity is governed by Newton's Law of Universal Gravitation. From https://en.wikipedia.org/wiki/Newton%27 ... odern_form


newtons law of universal gravitation wikipedia.jpg


So, no matter how far apart two bodies - or galaxies - are, the gravitational force between them will never be zero. The division by r² will make the force as close to zero as you want, but it will always be positive. However, when more than two objects are involved - which is the actual case in reality everywhere! - one body will always end up having the greatest force on another body, and "win" the tug of war. And then there is the added complication of all things being in motion with respect to others, which can prevent collisions (e.g. via orbits, as Chris was explaining) even though the force of gravity is unaffected.

I tried to find out if relativity modifies the standard law shown above, but google wasn't providing an answer. Surely though, near the surface of neutron stars, or near the event horizons of black holes, or when objects are moving at relativistic speeds, the equation for the law has to change, right? (I'm expecting terms like 1/√(1-(v²/c²) to make an appearance.)

Oh, and then there is dark energy (an apparent universal repulsive force!) which will also have to alter Newton's standard equation. Right?

The gravitational force between two bodies is exactly the same on both of them, no matter their individual masses. A grain of sand feels the same force from the Earth as the Earth feels from the grain of sand. Adding more bodies doesn't change this.

Of course, but I didn't imply otherwise, did I? I was merely trying to say that when more than two bodies are involved, one will have the greatest force and can win the "tug of war" and prevent collision with other bodies. Like, say, when you're sitting on the surface of the Earth, the Earth has won the tug of war with the Moon, and prevents you from colliding with the Moon, even though the force on you from the Moon is still there.

[orin stepanek]

More than you can shake a stick at!
Sorry; When I first saw this I read a Mess of Messiers; I must be losing it!