Astronomers have found further evidence that some galaxies grow in a way similar to snowflakes. A snowflake grows by building up ice crystals around a tiny grain of dust in the atmosphere. Likewise, some galaxies start off as modest “seed” galaxies within a cluster and then build up by acquiring stars from other galaxies in the cluster. This brief computer simulation shows the process (the bright dots in the simulation are the luminous cores of galaxies; notice how the one in the center grows to enormous proportions by grabbing stars from the other galaxies).
The authors of the new study observed the massive elliptical galaxy, NGC 1407, also commonly known as M87. Their case relies on measurements of the proportion of heavy elements in M87’s stars as a function of where they are located in the galaxy. The stars in the outer part of the galaxy have a different chemical composition than stars near the core, so it’s likely the galaxy wasn’t built all at once, but from the inside out like a snowflake. Not a gentle, delicate snowflake mind you: M87 is the most massive galaxy in the local universe, with a powerful black hole-driven jet of particles shooting out of its core at near-light-speed.