The Evolution and Distribution of Galaxies (Astronomy)

Recall cards on how galaxies formed, grew, and arranged themselves across the cosmos. Looking back in time: the 13.8-billion-year-old universe, the first stars within a billion years, the more than 2 trillion galaxies, and the tiny, blue, low-mass early galaxies seen at high redshift. Galaxy mergers: collisions far more common in the past, starbursts that burn through their gas in a few million years, the Tadpole and its tidal tail, NGC 6240's twin black holes, and galactic cannibalism. Large-scale structure: the cosmological principle, the Local Group, the Virgo and Coma clusters, superclusters, voids, and the sponge-like cosmic web. Dark matter: galaxy rotation curves, cluster mass-to-light ratios, gravitational lensing, MACHOs, and cold versus hot dark matter. And the assembly of structure: top-down versus bottom-up formation, red-and-dead ellipticals, and a universe that is about 5% atoms, 27% dark matter, and 68% dark energy.