Interstellar Dust

The gas and dust(often used interchangeably) in the interstellar medium plays a huge role in our understanding and observations of stars that are in the more distant reaches of the Milky Way. Our empirical knowledge of the existence of astronomical bodies relies heavily on our ability to analyze the electromagnetic radiation that these bodies radiate. In order to do so, we actually have to be able to see the light that these bodies radiate. However, due to the presence of interstellar dust, that isn't always feasible.

Interstellar dust specifically interacts with electromagnetic waves from background stars through a process known as interstellar extinction, causing it to dim from our point of view. This process is actually enacted through two underlying processes, notably in no particular order. The first process is absorption, where the interstellar dust absorbs the incident waves radiated from other stars. This means that light from the stars appears slightly dimmer because not all of their light reaches us. However, the absorption process isn't the main factor that dims the light from these stars. The main process of interstellar extinction that does this is the redirecting of light. About half the sunlight that falls on these interstellar grains of dust ends up being redirected, which means that the light won't reach us. This, in turn, dims our observations of distant stars heavily.