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ASTR 100 (38)
Lecture

Astronomy Lecture 38

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Department
Astronomy
Course
ASTR 100
Professor
Govindrajan
Semester
Fall

Description
Astronomy Lecture 38 12/2/13 Quasars and Active Galaxies 1. Galaxy redshift MAB a. Distance from redshift b. 3D Maps Show Cosmic Web c. First maps of the universe i. Initially only a few hundred galaxy spectra were used to  map  distribution ii. Velocity= H*Distance where H= 71 km/s per Mpc iii. Measure Doppler shift and estimate the distance 2. Radio sky discovered from Wheaton, IL a. 1936 Grote Reber built the fisrt radio dish in his backyard in Wheaton IL b. Discovered Sag A, Cas A, Cygnus A, etc. c. Contour maps of the sky showed “double sources in some cases 3. Objects between the two radio lobes a. 1954 Cygnus A (Peculiar galaxy) identified b. 1960’s many “stars” were identified between the double lobes c. All central sources are distant and show a high redshift in their spectrum 4. Nature of the central objects a. Very compact and extremely energetic b. Spectra often shows emission lines (these objects are not made up of stars) c. Emit all wavelengths of radiation from x­rays to radio d. Output energies 10 to 100 x all stars in an entire galaxy e. Only possible source of energy: a black hole in the nucleus of a galaxy 5. Names for these objects a. Quasar (quasi­stellar radio source)­ when a star like object sits between 
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