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Hubble's Messier 5

Explanation: "Beautiful Nebula discovered between the Balance [Libra] & the Serpent [Serpens] ..." begins the description of the 5th entry in 18th century astronomer Charles Messier's famous catalog of nebulae and star clusters. Though it appeared to Messier to be fuzzy and round and without stars, Messier 5 (M5) is now known to be a globular star cluster, 100,000 stars or more, bound by gravity and packed into a region around 165 light-years in diameter. It lies some 25,000 light-years away. Roaming the halo of our galaxy, globular star clusters are ancient members of the Milky Way. M5 is one of the oldest globulars, its stars estimated to be nearly 13 billion years old. The beautiful star cluster is a popular target for Earthbound telescopes. Of course, deployed in low Earth orbit on April 25, 1990, the Hubble Space Telescope has also captured its own stunning close-up view that spans about 20 light-years near the central region of M5. Even close to its dense core at the left, the cluster's aging red and blue giant stars and rejuvenated blue stragglers stand out in yellow and blue hues in the sharp color image.

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What is the current thinking on why globular clusters haven't formed into galaxies. ?
Or perhaps that is why have so many globular clusters formed into galaxies ??

RocketRon wrote:What is the current thinking on why globular clusters haven't formed into galaxies. ?
Or perhaps that is why have so many globular clusters formed into galaxies ??

I don't think the formation of globular clusters is understood well enough to ask your two questions, let alone answer them.

RocketRon wrote:What is the current thinking on why globular clusters haven't formed into galaxies. ?
Or perhaps that is why have so many globular clusters formed into galaxies ??

Just what I was wondering! Is there any open-source software with examples to play with to simulate this sort of thing? I've got a coupld of parallelas so I can do 64Gigaflops should I feel like it.

RocketRon wrote:What is the current thinking on why globular clusters haven't formed into galaxies. ?
Or perhaps that is why have so many globular clusters formed into galaxies ??

As a complete amateur, I can offer nothing more than speculation on these questions.

Globular clusters typically formed about 12 billion years ago, when the universe was incredibly different from today. It was many times smaller and many times denser, and it was churning with unused almost pristine gas, containing extremely small amounts of elements heavier than hydrogen and helium, and it was rife with raging star formation.

A globular cluster is typically the remnant of one incredible burst of star formation. Why didn't this "seed" keep growing into a full-fledged galaxy? Just possibly because that one burst of star formation was too "successful". It turned too much of the gas in its vicinity into stars all at once, and then the most massive of these newborn stars went supernova almost simultaneously, blowing the rest of the gas away.
I can't help thinking of nearby smallish galaxy M82. M82 is an incredible starburst galaxy, forming stars in its center at a phenomenal rate. But this galaxy is also blowing gas out of itself at a phenomenal rate. Its outer disk is completely devoid of recent star formation. It just could be that the violent star formation of M82 has doomed this galaxy to a premature old age, where stars in the not too far future will no longer form.

In the early universe, perhaps other mass concentrations, where stars formed at a more modest rate, could hold on to more of their own gas supplies and keep growing steadily, acquiring mass much more efficiently than the globular clusters.

But one globular cluster in the Milky Way is thought to be the core of a dwarf galaxy, Omega Centauri. This globular cluster managed to produce more than one burst of star formation and create a galaxy around itself, but it couldn't hold on to it. Both the core and the surrounding disk were too lightweight.

Ann

Crikies...'bout blinded me....seriously...need shades...oh...here.... ...lots better....

:---[===] *

As I've said in the past, something is wrong with the physics, age, or understanding of cluster theory.
If gravity exists (ha!), then after 13 billion years this cluster would have condensed into a massive black hole. It appears to have little "centrifugal" momentum to counteract gravity, as do disc shaped solar systems or galaxies. Someone answers, "oh, well each individual star has its own 'tangential velocity', but they are randomly oriented, hence no disc formation". But if the cluster's origin was a one-time event from a shared gas cloud, how could there have been individual, random, and no doubt even opposing momentums / orbits generated? Someone else says, "well, even with gravity, all motion is not uniformly 'inward': by close encounters, some stars are even ejected from the cluster". But forget not: in those encounters, the remaining star LOSES momentum, and hence SHOULD fall further towards the common center of gravity.
These clusters as described I believe defy Newtonian physics. But I don't think it's Newton who is wrong.....

tomatoherd wrote:As I've said in the past, something is wrong with the physics, age, or understanding of cluster theory.

Which "cluster theory" would that be? We don't have a good theory about the formation of globular clusters. But their behavior is accurately described by orbital mechanics.

If gravity exists (ha!), then after 13 billion years this cluster would have condensed into a massive black hole. It appears to have little "centrifugal" momentum to counteract gravity, as do disc shaped solar systems or galaxies.

There's no such thing as centrifugal momentum. There's no mechanism that would cause a cluster to collapse. Why do you think that gravity needs some counteracting force? Our solar system is 5 billion years old, and it hasn't collapsed. Like a star system, or a galaxy, a globular cluster is a collection of largely independently orbiting bodies. Orbits don't normally decay. The only reason a globular cluster could collapse would be if the individual stars in it lost angular momentum. Since there are no viscous processes, there is nothing to remove energy from the stars. They interact gravitationally, which simply transfers angular momentum. Stars that lose a little move into closer orbits; stars that gain it move outwards, and may be lost to the cluster. That's why clusters evaporate, they don't condense.

Someone answers, "oh, well each individual star has its own 'tangential velocity', but they are randomly oriented, hence no disc formation". But if the cluster's origin was a one-time event from a shared gas cloud, how could there have been individual, random, and no doubt even opposing momentums / orbits generated? Someone else says, "well, even with gravity, all motion is not uniformly 'inward': by close encounters, some stars are even ejected from the cluster". But forget not: in those encounters, the remaining star LOSES momentum, and hence SHOULD fall further towards the common center of gravity.

What difference does it make if the structure is a disk or a sphere? The dynamics of individual stars is no different. Even in disk galaxies, the majority of mass is found in the bulge, where the orbits are largely at random inclinations. Clusters may not have formed from a shared gas cloud. And even if they did, and started out as disks, there's no reason for them to stay that way. Disks aren't stable. Galaxies, too, evolve into ellipticals. When you perturb rotating disk structures, you gradually randomize the orbital inclinations of the members.

If a star loses ALL angular momentum, it will fall into the center. But that takes far longer on average than a few tens of billions of years for a structure like a globular cluster. In fact, the cluster evaporates faster, which just reduces the perturbations over time.

These clusters as described I believe defy Newtonian physics. But I don't think it's Newton who is wrong.....

Clusters demonstrate Newtonian physics. And you need nothing more than Newtonian physics to numerically model them, and the models behave just like what we observe.

Concerning the galaxy located behind M5, has an NGC number been assigned?

Just like open clusters, I imagine globular clusters to be formed in huge starforming regions. There is speculation that some of the earliest nebulae in the universe were much larger than ones that we can see now.

Chris:
thanks for your patient reply.
But, I can understand formation of a disc galaxy out of a primordial mass/cloud. And its resultant components are mostly orbiting the galaxy's center in the same direction. But I cannot wrap my head around how an even smaller mass could condense into individual components all moving in random directions (and be still so "unlumpy" after 13 billion years). It makes no sense.
I know there's no centrifugal momentum. That's why the quotes. But if the earth lost its tangential velocity suddenly, it would accelerate towards the sun. I know there's no frictional forces.
But accretion discs move to center, mergers occur in galaxy groups, etc, etc. Why are clusters so stable? I don't believe it. Yet I know Newton is not violated in observed clusters: each stellar orbit must perfectly balance the attractive force of gravity. It's the formation that boggles credibility.
And to me, 13 billion years is a loooong time.

Zoom in on the galaxy located behind M5, most likely, a number of the very small objects near the background galaxy in M5 are themselves globular clusters!

tomatoherd wrote:But, I can understand formation of a disc galaxy out of a primordial mass/cloud. And its resultant components are mostly orbiting the galaxy's center in the same direction.

Only while the primordial disk structure is maintained. But that's not a stable structure, and the period of reasonable stability is related to the stellar density. So even in a disk galaxy, most of the stars are not orbiting on the same plane or in the same direction. Only in the disk itself do we see that, where the stars are far enough apart that they don't perturb each other much.

But I cannot wrap my head around how an even smaller mass could condense into individual components all moving in random directions (and be still so "unlumpy" after 13 billion years).

This is the lowest energy state for a multiple-body orbiting system. It's what every such system eventually evolves into: a spherical structure, with the components in randomly inclined orbits, and a density gradient from the center to the outside. It's exactly what you get when you numerically model a large number of particles which are gravitationally bound and are controlled only by Newtonian dynamics.

How they initially condense (or form) is an entirely different question, which remains unanswered. But once you have condensed structures, their behavior is understandable, and globulars are well understood in this respect.

But accretion discs move to center, mergers occur in galaxy groups, etc, etc. Why are clusters so stable?

Accretion disks behave as they do because of viscous interactions (electromagnetic forces are important). Galaxies are much more diffuse, and their interactions occur over scales similar to their size (with the greatest part of the disruption occurring in the tenuous outer parts, not the cores). Globular clusters are very compact and located far from their parent galaxies with respect to their sizes. So they are not strongly influenced by tidal forces. They simply aren't exposed to much in the way of external perturbations. So most persist until they evaporate. Some, however, must be disrupted by tidal forces when they orbit too closely to a galaxy, or even come to close to another globular. But those are going to be statistically rare events.

And to me, 13 billion years is a loooong time.

To me, it's "we've only just begun".

Okay, Chris. I surrender.
I suppose since Galileo was at Pisa gravitation has continued to prove it just doesn't conform to human presuppositions.
But it appears at least I am not alone in perplexity over the formation stage.

redstar58 wrote:Concerning the galaxy located behind M5, has an NGC number been assigned?

Almost certainly not. There are a lot of M5 stars surrounding the galaxy, which is clearly quite distant and therefore (apparently) very small and faint. The V magnitude of M5 itself is about +6.65, and the brightest stars in it are about magnitude +12. Clearly the galaxy is not as bright as the brightest stars of M5. In view of the fact that the NGC catalogue was put together in 1888, chances are overwhelming that the galaxy had not been discovered at that time.

Ann

The formation of globular clusters may not be understood, but is the movement of its stars understood? Wasn't there something about some globular clusters condensing in the center, while others did not?

Also, if you look at the full sized photo, you will see several lines of stars that shouldn't be there if the star movements were random. I know we are good at seeing patterns, even in randomness, but the lines ARE real patterns that you could describe mathematically. I might expect one line of 12 or so stars of similar spacing and brightness, but there are over a dozen, some composed of over 20 stars. A few of the star lines are surrounded by areas of fewer stars than the average apparent density. Could this be caused somewhat by image processing?

tomatoherd wrote:I suppose since Galileo was at Pisa gravitation has continued to prove it just doesn't conform to human presuppositions.

It conforms to mine quite nicely. I don't think Newtonian gravitation deviates much from human intuition, and where it does, it doesn't take very much knowledge to overcome that.

But it appears at least I am not alone in perplexity over the formation stage.

There's hope that the next generation of space telescopes will let us observe them in the formation process.

Speaking of blue stragglers, there is one in the nearby universe, Algol in Perseus. The more massive component of a tight binary star turned into a red giant, filled its Roche lobe, and began spilling matter onto its smaller, more compact companion. The mass transfer went on until the former secondary star became the primary, now a blue B-type star about 90 times brighter than the Sun in V light. The former primary, by contrast, is now a shrunken, too small and faint red giant, only 4.5 times brighter than the Sun in V light.

Ann

Ann wrote:

redstar58 wrote:Concerning the galaxy located behind M5, has an NGC number been assigned?

Almost certainly not. There are a lot of M5 stars surrounding the galaxy, which is clearly quite distant and therefore (apparently) very small and faint. The V magnitude of M5 itself is about +6.65, and the brightest stars in it are about magnitude +12. Clearly the galaxy is not as bright as the brightest stars of M5. In view of the fact that the NGC catalogue was put together in 1888, chances are overwhelming that the galaxy had not been discovered at that time.

It's not even in NED... It's very, very hard to see a galaxy through such a bright foreground object.

It always amaze me how long these stars have lasted...

:---[===] *

FLPhotoCatcher wrote:The formation of globular clusters may not be understood, but is the movement of its stars understood? Wasn't there something about some globular clusters condensing in the center, while others did not?

Also, if you look at the full sized photo, you will see several lines of stars that shouldn't be there if the star movements were random. I know we are good at seeing patterns, even in randomness, but the lines ARE real patterns that you could describe mathematically. I might expect one line of 12 or so stars of similar spacing and brightness, but there are over a dozen, some composed of over 20 stars. A few of the star lines are surrounded by areas of fewer stars than the average apparent density. Could this be caused somewhat by image processing?

What we see as a straight line in 2 dimensions...may not be a straight line in 3 dimensions. As this is a picture of a ball of stars, they only appear "flat" and "straight". The stars are actually closer, or further away and in an arc...

:---[===] *

Several of the stars have a red ring-like object to their left (some better seen in the enlarged image when clicking on the APOD when online). I wonder if they are image artefacts but if so I'm curious why they only seem to be on the immediate left of the stars.

DavidLeodis wrote:Several of the stars have a red ring-like object to their left (some better seen in the enlarged image when clicking on the APOD when online). I wonder if they are image artefacts but if so I'm curious why they only seem to be on the immediate left of the stars.

Well, they are only visible in the red channel, which makes me think they are out-of-focus reflections of the bright stars (donut shaped because that's what the aperture looks like) visible only with the 814W filter. Possibly the AR coating on that filter is less efficient in the IR? The offset could be caused by the tilt of the filter, either incidental or by design. In any case, they're clearly imaging artifacts.

Chris Peterson wrote:

DavidLeodis wrote:Several of the stars have a red ring-like object to their left (some better seen in the enlarged image when clicking on the APOD when online). I wonder if they are image artefacts but if so I'm curious why they only seem to be on the immediate left of the stars.

Well, they are only visible in the red channel, which makes me think they are out-of-focus reflections of the bright stars (donut shaped because that's what the aperture looks like) visible only with the 814W filter. Possibly the AR coating on that filter is less efficient in the IR? The offset could be caused by the tilt of the filter, either incidental or by design. In any case, they're clearly imaging artifacts.

Thanks Chris . It was their donut shapes that particularly caught my interest. Mmmmm, I fancy a or two now.

DavidLeodis wrote:

Chris Peterson wrote:

DavidLeodis wrote:Several of the stars have a red ring-like object to their left (some better seen in the enlarged image when clicking on the APOD when online). I wonder if they are image artefacts but if so I'm curious why they only seem to be on the immediate left of the stars.

Well, they are only visible in the red channel, which makes me think they are out-of-focus reflections of the bright stars (donut shaped because that's what the aperture looks like) visible only with the 814W filter. Possibly the AR coating on that filter is less efficient in the IR? The offset could be caused by the tilt of the filter, either incidental or by design. In any case, they're clearly imaging artifacts.

Thanks Chris . It was their donut shapes that particularly caught my interest. Mmmmm, I fancy a or two now.

We had a discussion about these donut artifacts the last time this image was run. I have looked all through the raw data to find out where they came from but never quite figured it out. If I had to guess I would say it came about by combining two F814W filters because all of the exposures have a lot of charge bleeds in them. So what you can do is combine a couple of them taken while the telescope was at different orientations and fill in the white streaks with real data from a second dataset. Somehow, some way, those annuli ended up there. I can't ask the image processor because ESA never credits them, much to my annoyance.