Lecture20 - Astro Nova NASA projects massive job cuts Space...

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Astro Nova NASA projects massive job cuts Space Shuttle program ends in 2010 ~8,000 contractor positions to go Constellation not to fly until 2015 New Director for NOAO David Silva begins 5-yr term
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Previous Lecture Standard Candles Cepheid Period-Luminosity relation Tully-Fisher relation rotation – luminosity correlation Supernova Ia light curve shape correction Redshift-Distance relation v = H 0 d Hubble constant: H 0 = 72 ± 3 km/sec/Mpc
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Quiz Question #1 The longer the period of a Cepheid variable star, the: A. nearer it is B. more distant it is C. brighter it is D. fainter it is E. more slowly it moves within its galaxy
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Active Galaxies Rare galaxies with very luminous central regions core appears point-like (stellar), with luminosity > 2.5 x 10 10 L sun optical spectra show strong broad emission lines from ions with a wide range of energies non-thermal emission from radio to X-ray jets: oppositely-directed flows of matter, sometimes moving near speed of light rapid brightness variations (days-weeks)
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Types of Active Galaxies Radio galaxies L radio > 10 37 –10 38 watts synchrotron emission from high speed electrons in magnetic fields typical of morphology < pc size central source two narrow jets, ~10 Kpc long, outer lobes of size 50 – 1,000 Kpc material flows out the jets to the lobes
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Superluminal Motions Seen in radio jets projection effects of subluminal, but high speed, motions
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Seyfert Galaxies spiral galaxies with bright, blue nuclei
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Lecture20 - Astro Nova NASA projects massive job cuts Space...

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