NATS 1740 Chapter Notes - Chapter 20: Spiral Galaxy, Cosmological Principle
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NATS 1740 Full Course Notes
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Chapter 20: galaxies and the foundation of modern cosmology. Cosmology- the study of the overall structure and evolution of the universe. Spiral galaxies- flat white disks with yellow bulges at the centre. Disk is filled with cool gas and dust with hot ionized gas and have spiral arms. Elliptical galaxies- appear rounded in shape and longer in one direction. Have no disk or cool gas, but often contain hot ionized gas. Irregular galaxies- galaxies that are neither spiral or elliptical. Disk component- portion of the spiral galaxy that contains cool gas and dust. Stars of all ages are found here that follow circular orbit around the galactic centre. Halo component-includes the halo and the centre bulge. Contains old stars and very little cool gas/dust. Blue cloud-galaxies have many young hot stars and have active star formation because of the cool gas clouds. Red sequence-galaxies that contain only older stars and are elliptical in shape.