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| Active Galaxies and Quasars |
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1. | The dusty torus around the black hole in NGC 4261 has an angular diameter of about 1.6 arc seconds in the widest direction. How wide is that in light years if we know that the galaxy is about 30 Mpc away? |
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2. | Compare the relative sizes of 1 solar mass black hole with a normal star companion of 1 solar mass in a binary system. How large, relative to the approximately 800 light year diameter torus imaged by the Hubble Telescope in NGC 4261, would the central black hole be if it has a mass of 1 billion solar masses? |
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3. | How far does light travel in one hour? |
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4. | How many kilometers are in a light week (the distance light travels in a week)? |
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5. | The best resolution obtainable with the Hubble Space Telescope is about 0.05 seconds of arc. What is the minimum diameter region that the HST can resolve in the center of the giant elliptical galaxy M87, which you may assume to be at a distance of 18.4 Mpc. Compare this with the expected size of a billion solar mass black hole. If there is a black hole of this mass at the center of M87 (as suggested by many observations) could the Hubble Space Telescope resolve it? |
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6. | The nearest AGN is about 2.9 Mpc away. With a resolution of 0.05 arc seconds, what is the minimum size region that the Hubble Space Telescope could resolve in its center. How does this compare with the expected size of a billion solar mass black hole? |