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M72: A Globular Cluster of Stars

Explanation: Globular clusters once ruled the Milky Way. Back in the old days, back when our Galaxy first formed, perhaps thousands of globular clusters roamed our Galaxy. Today, there are less than 200 left. Many globular clusters were destroyed over the eons by repeated fateful encounters with each other or the Galactic center. Surviving relics are older than any Earth fossil, older than any other structures in our Galaxy, and limit the universe itself in raw age. There are few, if any, young globular clusters in our Milky Way Galaxy because conditions are not ripe for more to form. Pictured above by the Hubble Space Telescope are about 100,000 of M72's stars. M72, which spans about 50 light years and lies about 50,000 light years away, can be seen with a small telescope toward the constellation of the Water Bearer (Aquarius).

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Looks kinda like any other run of the mill section of space that has a conglomeration of white spots -- Until you click on the picture once or twice -- then it becomes one of those "wow" shots

Back in the "old days"?
Not any older than six thousand years!

With a globular cluster, what are the dynamics that form the group? Are they static in relationship with each other? Or are they moving in to a central point or expanding? If gravity is the driving power behind elliptical galaxies that have spin, what happened to Globular?

My understanding is that the stars in globular clusters do 'pincushion' orbits, mostly, about the centre of mass by gravitational action. However, I have no observational data on this.

Thanks, APOD! This is a good one !
I'd never seen a globular cluster be so exciting before !!!
It is odd, as to why our galaxy would have 200 roaming 'banditos' so to speak, as per the mainstream of starcreation in the arm structures.

Now, as to the 'age' of globular clusters, that is another matter entirely.

Great image! I like the background galaxies most! There are really nice edge-on ones!

Does anyone of you know what these orange to red dots are that appear all over the image?

I was wondering some of the same things that tesla (above) mentioned. What is different in the gravitational forces that cause some globular clusters to apparently resolve themselves into a disk-like galaxy as our galaxy but others still remain as globular clusters? What kind of rotational motions do they have?

biddie67 wrote:I was wondering some of the same things that tesla (above) mentioned. What is different in the gravitational forces that cause some globular clusters to apparently resolve themselves into a disk-like galaxy as our galaxy but others still remain as globular clusters? What kind of rotational motions do they have?

Good question!
I'm looking forward to the answer! I could only imagine that for any reason star-forming went much faster in globular clusters than in galaxies.

Great APOD today,
THANK YOU by me and bt my heart!!!
stefanodrin

Anyone know why some of the larger (and possibly nearer) objects display the diffraction spikes but not the smaller objects? Does this have to do with the fact that aren't enough photons from the smaller ones to diffract off the mirror supports? Or that there will always be the diffractions but not enough to see them on the image? Thanks.

Vincent,

I assumed the diffraction spikes were caused by stars that are within our galaxy, and therefore closer and brighter. I've seen other images like this, and that has been the explanation in the past. I have no idea if I'm right, however!

M72 is in our own galaxy.

tesla wrote:With a globular cluster, what are the dynamics that form the group? Are they static in relationship with each other? Or are they moving in to a central point or expanding? If gravity is the driving power behind elliptical galaxies that have spin, what happened to Globular?

The stars are gravitationally bound, which means all are in orbits around their perceived center of mass. That is generally at the center of the cluster, of course, but since the star density is so high, the individual stars interact with their neighbors as well. The result is that each star follows a highly perturbed orbit. Occasionally, a star is sufficiently perturbed to be ejected from the cluster completely- a process called evaporation. This limits the lifetime of a globular cluster to the order of 10 billion years.

Hofi wrote:Great image! I like the background galaxies most! There are really nice edge-on ones!

There are also some lovely spirals!

And agree: great image!

owlice wrote:

Hofi wrote:Great image! I like the background galaxies most! There are really nice edge-on ones!

There are also some lovely spirals!

You are right! If you have a close look, you can even see some background nebulae! ... Really great stuff!

I agree: a great image!

bystander wrote:M72 is in our own galaxy.

I'm not sure what is meant by "in" our own galaxy. I was under the impression that most globulars orbit the galactic center but aren't part of the galactic disc. M72 is about 53,000 light years from the galactic center but the dimensions of the galactic disc are approx 12,000 x 100,000 light years so it might or might not be part of the disc. I found this picture that shows globular outsides of the galactic disc. Does any know where M72 is located with respect to the galactic disc?

KJackson wrote:Does any know where M72 is located with respect to the galactic disc?

Courtesy of Think Astronomy Software.

Lovely picture. Clicking on it when online brings up a wider field-of-view that has some galaxies that are not seen in the APOD. There is a particularly large spiral galaxy to the bottom left corner. I wonder what that galaxy is called (assuming that it has a name)?
<<< those two smilies are from the "View more smilies" link. The owl is cute!

DavidLeodis wrote:Lovely picture. ... The owl is cute!

I agree!!

owlice wrote:

DavidLeodis wrote:Lovely picture. ... The owl is cute!

I agree!!

I ed at that. The is a smilie for your member name owlice.

Since these represent some of the oldest in the galaxy and the stars are relvatively close together - far closer than the stars in our neighborhood - I have to wonder about the forms of life that might exist within these clusters. If life forms there have evolved and survived, might their proximity to each other possibly create the kind of scenarios as depicted in our more popular science fiction? Scenarios where differing life forms interact with some regularity. It is an intriguing thought.

sirnelson wrote:Since these represent some of the oldest in the galaxy and the stars are relvatively close together - far closer than the stars in our neighborhood - I have to wonder about the forms of life that might exist within these clusters. If life forms there have evolved and survived, might their proximity to each other possibly create the kind of scenarios as depicted in our more popular science fiction? Scenarios where differing life forms interact with some regularity. It is an intriguing thought.

It is generally thought that planetary systems are rare to non-existent in globulars, because gravitational perturbations from nearby stars will make them unstable. Any planets that survive are likely to be very close to their parent star, and therefore poor candidates for any sort of life as we imagine possible.