sentence1: the milky way , which is a prototype of the galaxies that are responsible for most of the luminosity in the universe , is known to possess all the components listed above , and kinematic mapping of these with gaia offers a unique opportunity to clarify some of the fundamental questions of contemporary astronomy .
sentence2: the milky way is the best-studied non-agn dominated star-forming galaxy , and the only galaxy that direct measurements of cr intensities and spectra are available .