Supermassive Black Holes Make Merging Galaxies Green
Green as a color can mean animal, vegetable or mineral. It is the stuff of crocodiles, chlorophyll and copper patina, the essence of serpentine or of snakes in the grass, the hue of a glacial lake, a stagnant pond and the Chicago River on St. Patrick’s Day. Green seems to be everywhere you look—everywhere, that is, but up. As ubiquitous as it is on Earth, green is almost entirely absent from the heavens. There are exceptions...