There are many facts explained in Dhamma with regards to the existence and the universe. If we talk about galaxies described in Dhamma it is like this.
We already know about the 31 planes of existence. Each set of 31 planes has a sun and moon to give light to them. And it is known as a “World Component (Loka Dhãthuwa)”… or we say it as a Galaxy which include 31 planes.
1000 of world component are known as “Thousand Worlds component / 1000 Galaxies” (Sahasshri Loka Dhãthuwa) also named as Chulani World Component.
This kind of “Thousand worlds component” multiply by 1000 again and we get “Ten thousand Worlds component / Ten thousand galaxies” (Dwi sahasshri loka Dhãthuwa) and also known as “middle world component”
And then when we multiply the middle world component by 1000 again we get the “Great World component also known as Thrisahasshri Loka Dhãthuwa”
And person with miraculous powers comes from Jhana or absorption can understand up to Thousand World component / 1000 Galaxies which call as Sahasshri Loka Dhãthuwa / Chulani World Component. If they want they can communicate to the beings in this 1000 world component/ galaxies.
Samma Sambuddha has the power to preach or even visit & give an effect of Dhamma up to “Great World Component / Great Galaxy”. Some of the chanting (pirith) are known to be spread around all these galaxies. And there were some miraculous things happen in all these galaxies in many ways when some special things happen with regards to the Samma Sambuddhas. In Dhamma we get an idiom to express how vast is this universe. It says,
“If one took mustard seeds which can filled the millions of galaxies and start to walk by giving each mustard seed to each galaxy one by one still the mustard seeds will be finish but not the number of galaxies finishes”
May all beings be well and happy & attain the fruits of Nibbana.