ASTR 1103 Lecture Notes - Lecture 16: Elliptical Galaxy, Gravitational Lens, Ring Galaxy
9 Feb 2020
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Document Summary
Clusters of galaxies: rich clusters more than 1000 galaxies, spherical, 10 million ly diameter, poor clusters less than 1000 galaxies, irregularly shaped. Coma cluster: rich cluster of galaxies located in coma berenices, 300 million ly from earth, giant elliptical and close to center. Local group: example of a poor cluster, contains less than 1000 galaxies, about 4 million ly in diameter, mixture of elliptical, spirals, and irregulars. Dark matter in galaxy clusters: difference between: visible mass of cluster (luminosity) and gravitational mass of cluster (orbits of galaxies in cluster, gravitational lensing) is attributed to dark matter. Gravitational lensing: allows measuring of gravitational mass, massive object (galaxy cluster) bends light from a distant galaxy creating two images (mirage) or an einstein ring. Tidal interactions: are gravitational interactions like the tides on earth, barred spirals may be produced by tidal interactions. Galactic cannibalism: another name for the merger of galaxies. Starburst galaxies: galaxies undergoing a rapid burst of star formation.
