How do astronomers think the sun may have begun?

How can scientists test their ideas about the origin of the universe if they can't physically interact with or study?

Plz ! ive been stuck on this forever

Actinobacteria sp. are fermenting organisms (which do you use oxygen to breathe) referred to as chemoorganohetereotrophs this means they break down organic material and convert it to inorganic material. which part of the carbon cycle does this describe