What is the unified model of active galactic nuclei? How does it explain differences in the continuous spectrum and emission lines of an active galactic nucleus?
What will be an ideal response?
A supermassive black hole is the centerpiece of the unified model. According to the unified model, what you see when you view the core of an active galaxy depends on how the black hole's accretion disk is tipped with respect to the observer's line of sight.
If the accretion disk is viewed edge-on, the central area cannot be seen because the thick, dusty outer torus of the accretion disk blocks the view of the center. The visible gas is further from the central black hole. It is cooler, orbits more slowly, and produces less broad spectral lines. The hottest gas cannot be seen because it is obscured by the cool edge of the accretion disk.
If the accretion disk is tipped away from edge-on, the observer can see more of the hot gas in the central cavity of the accretion disk. This region emits broad emission lines because the hot gas is orbiting at very high velocities. The view of hotter gas allows more X-ray emission to be seen.
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A(n) _____________material has properties that are equal in three perpendicular directions.
Fill in the blank(s) with the appropriate word(s).
From center to surface, which of the following correctly lists the interior layers (defined by density) of a terrestrial world?
A) core, mantle, crust B) mantle, core, crust C) mantle, crust, core D) core, crust, lithosphere
The Earth is instantly replaced in its orbit by a speck of dust. Which statement best describes the subsequent orbital motion of that piece of dust?
A) The dust particle will move to a larger orbit and orbit the Sun in more than 1 year. B) The dust particle will continue in the same orbit as the Earth did, orbiting the Sun in 1 year. C) The dust particle will move to a smaller orbit and orbit the Sun in less than 1 year. D) The dust particle will spiral into the Sun. E) The dust particle will be ejected from the Solar System.
Magma that solidifies before reaching Earth's surface is called
A) intrusive igneous rock. B) plutonic rock. C) a pluton. D) all of the above.