A Globular cluster (GC) is fascinating because gravity only attracts so eventually there should be a collapse or at least collisions within the GC, but they have been moving around perhaps billions of years.
On the web I found this explanation for GC stability:
Even within a globular cluster where the typical separation of stars in a globular cluster is around 1 light year (thus star-star collisions are rare). Hence binary stars can orbit each other, and globular clusters can remain stable for literally billions of years.
I feel this explanation is not justified when only gravity is involved. Gravity is known as a weak force but if is so weak that it can't bring stars together when most of them are at a similar distance of only 1 light year, than how can gravity be so strong to maintain the globular structure lasting billions of years? This is not a coherent explanation.
DeepSkyVideos on youtube had a good description of the orbit for M10 GC around the Milky Way. A link is attached.
This description makes a GC even more interesting. Astonomers claim gravity is the force holding the stars together in the cluster. M10 has an elliptical orbit around the core of the Milky Way so its path takes it through the galactic plane. The video mentions a paper that analyzed M10. As the GC passes through this plane of many stars there is a trivial attrition, where some stars are stripped from the GC. This conclusion means the gravity in the GC is strong enough to maintain its shape and to hold most of its members even though periodic disruptions through the galactic plane. It also means passing through the galactic plane does not trigger more collisions within the GC or even its collapse.
I wonder if EUT can offer a better explanation for GC behaviors.
There is a repulsive force within the cluster. The sun and stars are positively charged being predominantly ionized hydrogen. The electric fields of the positively charged stars should inhibit collisions by their electric fields, since + repels +. Astronomers generally ignore plasma and electromagnetic effects but a GC reveals the usefulness of an electric field from a positively charged body when there are so many in a relatively small volume.
I am not competent to explain a GC but a simple observation of several show the stars are generally uniform, implying a similar size and so similar electric fields. There are more stars at the center with the density decreasing as stars are further from the center. The observation implies gravity holds the general shape while all the individual members are repelling all the other members. There is no defined outer edge for this shape held together so loosely in this manner. With this explanation for a very loose structure, when M10 passes through the galactic plane the GC behaves like a bundle of ballons tied together by a string; so with a bump they just jostle around.
M10 has an orbital period in millions of years but it has passed through the plane many times and remains a GC.
The mechanism for the creation of a globular cluster is not known.
From an astronomy.com article:
Thanks to the NASA/ESA Hubble Space Telescope, some of the most mysterious cosmic residents have just become even more puzzling. New observations of globular clusters in a small galaxy show they are very similar to those found in the Milky Way, and so must have formed in a similar way. One of the leading theories on how these clusters formed predicts that globular clusters should only be found nestled in among large quantities of old stars. But these old stars, though rife in the Milky Way, are not present in this small galaxy, and so the mystery deepens.
Globular clusters — large balls of stars that orbit the centers of galaxies but can lie very far from them — remain one of the biggest cosmic mysteries. They were once thought to consist of a single population of stars that all formed together. However, research has since shown that many of the Milky Way's globular clusters had far more complex formation histories and are made up of at least two distinct populations of stars.
Of these populations, around half the stars are a single generation of normal stars that were thought to form first, and the other half form a second generation of stars, which are polluted with different chemical elements. In particular, the polluted stars contain much more nitrogen than the first generation of stars.
The proportion of polluted stars found in the Milky Way's globular clusters is much higher than astronomers expected, suggesting that a large chunk of the first-generation star population is missing. A leading explanation for this is that the clusters once contained many more stars, but a large fraction of the first-generation stars were ejected from the cluster at some time in its past.
This explanation makes sense for globular clusters in the Milky Way, where the ejected stars could easily hide among the many similar old stars in the vast halo, but the new observations, which look at this type of cluster in a much smaller galaxy, call this theory into question.
Astronomers used Hubble's Wide Field Camera 3 to observe four globular clusters in a small nearby galaxy known as the Fornax Dwarf Spheroidal Galaxy.
"We knew that the Milky Way's clusters were more complex than was originally thought, and there are theories to explain why. But to really test our theories about how these clusters form, we needed to know what happened in other environments," said Soren Larsen of Radboud University in Nijmegen, the Netherlands. "Before now, we didn't know whether globular clusters in smaller galaxies had multiple generations or not, but our observations show clearly that they do!"
The astronomers' detailed observations of the four Fornax clusters show that they also contain a second polluted population of stars and indicate that not only did they form in a similar way to one another, but their formation process is also similar to clusters in the Milky Way. Specifically, the astronomers used the Hubble observations to measure the amount of nitrogen in the cluster stars and found that about half of the stars in each cluster are polluted at the same level that is seen in Milky Way's globular clusters.
This high proportion of polluted second-generation stars means that the Fornax globular clusters' formation should be covered by the same theory as those in the Milky Way.
Based on the number of polluted stars in these clusters, they would have to have been up to 10 times more massive in the past before kicking out huge numbers of their first generation stars and reducing to their current size. But, unlike the Milky Way, the galaxy that hosts these clusters doesn't have enough old stars to account for the huge number that were supposedly banished from the clusters.
"If these kicked-out stars were there, we would see them, but we don't!" said Frank Grundahl of Aarhus University in Denmark. "Our leading formation theory just can't be right. There's nowhere that Fornax could have hidden these ejected stars, so it appears that the clusters couldn't have been so much larger in the past."
This finding means that a leading theory on how these mixed-generation globular clusters formed cannot be correct, and astronomers will have to think once more about how these mysterious objects in the Milky Way and further afield came to exist.
I find globular clusters mysterious and so do astronomers. Perhaps my simple analogy is wrong. Astronomers expected to find stars ejected from a GC but found none; they concluded their current theory is wrong.
Later I added this comment:
My simple analogy is too simple; there are certainly more forces involved to keep the observed spacing between stars within the cluster.
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