In a binary star system, we have two stars, each with their center of gravity. Then, we also have both stars circling one another around what is called the barycenter. This is then also a gravitational center, though no mass is found in the location.
It's like two ice skaters holding each other's hands, circling one another real fast. The gravitational center between them is understood with their spin, their velocity, their mass.
There is nothing mysterious about this.
In a binary star system, the center spot around which both circle is not considered to have much gravity. Yet there is some.
Known are, for instance, LaGrange points. Here is an article, or look up LaGrange points:
https://solarsystem.nasa.gov/faq/88/what-are-lagrange-points/#:~:text=Lagrange%20Points%20are%20positions%20in,position%20with%20minimal%20fuel%20consumption.
Two bodies attract one another, but their velocity through space prevents them from becoming one mass. Instead, the two stars circle one another. About half the star systems are considered to be binary star systems (not sure if this information needs updating).
In between we have a gravitational phenomenon of some kind.
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When we move from a binary-star system to a ten-star system, something disappointing happens in physics. Two bodies, and three bodies, can get calculated by physicists, but they can't calculate the results of systems with more than three bodies (celestial masses). So, basically they are a bit blind when discussing multiple stars in a system.
With a ten-star system, we should still have a barycenter in the middle among all of them. Ask physicists, and none of them will declare that there is a mass in the barycenter.
Go for 100-star system and you can imagine that the pull on that barycenter by all celestial masses increased by quite a bit.
Same for the ice skaters. Two ice skaters circling one another will have their hands getting pulled by their partner in oppositional direction. Yet ten ice skaters all holding on to one another, circling around one center, that will put greater pressures on the two or more hands holding each other exactly in the center.
With 100 ice skaters all circling this group, holding on to one another, the center spot will experience a great pull indeed, while the ice skaters on the outside of the group may either go real fast, or help slow down the circulation altogether.
Again, an analogy that is not perfect but that should help you see that celestial masses attract one another, while there are other circumstances that prevent all masses from becoming a single mass. We find a dynamic outcome.
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The big surprise is that physicists work with two different models without pointing them out, not even discussing this.
The binary-star system, and the star systems with five, ten, or 100 stars, are not considered to have an invisible mass in the center. Nothing is said about an event horizon for these examples.
Yet with a galaxy, and therefore something like 100,000,000 stars in one system, we 'all of a sudden' have an invisible mass, an event horizon.
So, that is the conundrum, bkuehlhorn. Physicists are swapping models between the few stars in a system on the one hand and the many stars in a galactic system on the other hand. And worst of all is that they don't address it. They are silent about their own thinking, swapping models, and not giving a single thought to it.
