WHICH ONE BLACK HOLE OR GALAXY CAME FIRST ????

Hello everyone myself Prince kumar samariya and I am here with a very interesting topic and we will try to findout the answer of a very interesting question. So let's get started.

Whenever we think about black hole and galaxy we become very excited.Everyone wants to know everything single thing about black hole and galaxy. But did you ever thing which one black hole or galaxy  came first ?

Well this is very interesting question. Because when ever we observe galaxies across the universe, we find that most of them have super-massive black holes in their centers. For example,  Our own Milky Way galaxy has a black hole of about 4 million solar masses. This connection between black holes and galaxies raises an interesting question regarding the origin and evolution of galaxies. Did early galaxies form around black holes, or did black holes form within young galaxies? In other words, which came first, the black holes or the galaxies?

We’ve recently looked at both the largest and the smallest black holes in the Universe, and this gives us the wonderful opportunity to look at the order in which the different structures in the Universe formed. On the largest scales, this is what the Universe looks like!

If we’re asking the question of whether the large black holes at the center of galaxies came before the galaxies themselves or whether the galaxies formed first and then developed black holes at their centers, we’re really asking the following question: did the Universe form structure on the smallest scales first, or on the largest scales?

For decades, this was an ideological argument primarily between Americans, who favored a bottom-up approach, and Soviets, who favored a top-down approach. Here’s the difference:

• Top-down: The Universe starts off with large-magnitude fluctuations on large scales and not on small scales. The overdense regions, being very large, gravitationally collapse down from irregularly-shaped triaxial ellipsoids along their shortest axis, forming pancake-like structures that fragment apart into galaxies. At later times, these galaxies evolve and grow black holes in their centers; the galaxies would form before the black holes in this scenario.In simple words supercluster-sized clouds of gas collapse upon themselves. These clouds then fragment into galaxy-sized clouds that continue to collapse into full-fledged galaxies. The stars and dust within the centers of these galaxies eventually collapse into black holes that grow to supermassive size over time. This model is similar to the way stars form within stellar nurseries, where lots of stars are born from a single large cloud.
• Bottom-up: The Universe starts off with large-magnitude fluctuations on small scales and not on large scales. The overdense regions grow over time, producing small mass clumps that grow, merge, and cluster together, eventually growing into large galaxies and clusters of galaxies. In this scenario, black holes would form first along with small stellar clumps, and only at much later times would they grow into what we consider galaxies. Simply In this approach small pockets of gas collapse first, which then merge to form galaxies. These galaxies then form into clusters and superclusters later on. In this model stars and black holes would tend to form before galaxies.

Both models have some observational evidence to support them. When we look at the distribution of galaxies across the universe, for example, we find that they are grouped into clusters and superclusters at all scales. This is what you would expect if the early universe had the initial supercluster-sized clouds of the top down model. But we also see early fluctuations on a small scale. In particular, the effects of cold dark matter come into play early on, so star formation (and likewise the formation of black holes) began early on as well. This is further supported by the fact that within 400 – 500 million years after the big bang the first stars were already shining. So basically it looks like both the top down and bottom up processes contributed to the to the process. Galaxies formed through a process of mergers, but those protogalaxies were already part of a large supercluster structure.

But while both processes seem to play a role, the bottom up process has an advantage. That’s because gravitational interactions between masses don’t occur instantly. Gravitational disruptions travel the universe at the speed of light, so interactions on a small scale have a leg up. 

So to the best of our knowledge, that’s what we get: a Universe where stars and black holes form early on, then galaxies both form around them and form by these young, small regions merging together. Over time, they grew to the enormous supermassive black holes and the enormous galaxies we see today. But it takes initial, comparably-sized fluctuations on both the small and large scales to reproduce what we see in our Universe.

It’s knowing all this that informs how all the structure in the Universe formed, evolved and continues to grow over time, even all the way up to the present day.

So the best answer we have is that the seeds of supermassive black holes and the seeds of galaxies were what formed first, and they did so at approximately the same time. But these black holes began as quite large structures, growing to at least many thousands of solar masses before the environments in which they were housed could ever be considered galaxies, and so it appears that black holes came first, but they form in regions that will merge-and-grow into large, rich galaxies in very short order.

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P. SAMARIYA

[PRINCE KUMAR SAMARIYA]