Galaxies are made up of stars, gas, dark matter and dust. That last ingredient is only a small amount of the total but radically changes our view of galaxies. Up to half the starlight in a given galaxy could be invisible thanks to the small amount of dust. Over decades, astronomy has sought to get away from dust to study the galaxies’ stars and to study the dust itself.
I study this dust, specifically how it dims and reddens the starlight in galaxies other than our Milky Way. It is tricky to identify if a part of a galaxy is dark because the stars are hidden by dust or simply because there is nothing there.
I will talk about some of the techniques I’ve used to find where and how much dust there is in the swirls of spiral galaxies. Lately, accidentally overlapping galaxies show in vivid detail where the dust spread throughout the foreground galaxy. These make for some spectacular Hubble images.