The Shapes of Galaxies

ick up any photograph of a Hubble deep field and look carefully. In a single image spanning a patch of sky smaller than a grain of sand held at arm's length, hundreds of galaxies are visible. They are not all the same. Some are smooth oval glows. Some are flat blue disks with spiral arms. Some are wrapped around each other in gravitational embraces. Some are so faint they are barely there. This book explains what all of those different shapes mean and why they exist.The Shapes of Galaxies is a complete scientific account of galaxy morphology for adult readers, covering the full range from the largest elliptical giants at the centers of galaxy clusters to the smallest ultrafaint dwarfs containing more dark matter than stars. You will understand why spiral galaxies have arms (density waves that compress gas and trigger star formation, not rotating fixed structures), why elliptical galaxies are red and smooth (they formed in rapid early mergers that exhausted their gas and scrambled their disk structure), why lenticular galaxies look like spirals without arms (former spirals stripped of their cold gas by cluster environments), and why some of the most spectacular galaxies in the universe are ordinary galaxies in the act of colliding.Twelve chapters cover every major galaxy type in depth: spirals and the physics of the Tully-Fisher relation, barred spirals and how the bar channels gas to the center to fuel star formation, ellipticals and the violent relaxation that produces their smooth profiles, lenticulars as cosmic archaeologists of the quenching process, dwarf galaxies as the most dark-matter-dominated objects known, mergers and the tidal features that persist for billions of years as fossil records, and the full history of how galaxy morphologies have changed across 13 billion years of cosmic time. The final chapter covers what the James Webb Space Telescope has found in the first billion years of cosmic history, including disk galaxies that formed earlier than any model predicted and elongated structures with no counterpart in the nearby universe.Part of the Stars and Galaxies Adult Series.

ick up any photograph of a Hubble deep field and look carefully. In a single image spanning a patch of sky smaller than a grain of sand held at arm's length, hundreds of galaxies are visible. They are not all the same. Some are smooth oval glows. Some are flat blue disks with spiral arms. Some are wrapped around each other in gravitational embraces. Some are so faint they are barely there. This book explains what all of those different shapes mean and why they exist.The Shapes of Galaxies is a complete scientific account of galaxy morphology for adult readers, covering the full range from the largest elliptical giants at the centers of galaxy clusters to the smallest ultrafaint dwarfs containing more dark matter than stars. You will understand why spiral galaxies have arms (density waves that compress gas and trigger star formation, not rotating fixed structures), why elliptical galaxies are red and smooth (they formed in rapid early mergers that exhausted their gas and scrambled their disk structure), why lenticular galaxies look like spirals without arms (former spirals stripped of their cold gas by cluster environments), and why some of the most spectacular galaxies in the universe are ordinary galaxies in the act of colliding.Twelve chapters cover every major galaxy type in depth: spirals and the physics of the Tully-Fisher relation, barred spirals and how the bar channels gas to the center to fuel star formation, ellipticals and the violent relaxation that produces their smooth profiles, lenticulars as cosmic archaeologists of the quenching process, dwarf galaxies as the most dark-matter-dominated objects known, mergers and the tidal features that persist for billions of years as fossil records, and the full history of how galaxy morphologies have changed across 13 billion years of cosmic time. The final chapter covers what the James Webb Space Telescope has found in the first billion years of cosmic history, including disk galaxies that formed earlier than any model predicted and elongated structures with no counterpart in the nearby universe.Part of the Stars and Galaxies Adult Series.