Hello :).
Happy to offer help/advice :).
Yes, it sounds like what you’re trying to achieve is similar to this:
To make that video, I use NASA’s Horizon’s app do download orbital parameters for asteroids/comets in CSV format. I then used csv->datatable in unreal engine to get the orbital parameters for each asteroid into datatable form where I could access the data. Then, I made an instanced mesh (just a simple sphere) and used MaxQ/Spice to update the position of each asteroid and the earth for a given time.
5M galaxies might work similarly if you can get the data for them.
As an aside, I think it’s interesting in the video linked above that you can see “swirls” form over time in the rendering of the asteroids. It took a minute to realize what was happening… Because the video plays out over time the “swirl” is following earth… Which, is discovering and cataloging the asteroid data used to render the video. So, wherever the earth is, that’s where the asteroid field becomes densest - because that’s where updated data was which placed the asteroid near earth at the time :).