According to the model in which active galactic nuclei are powered by supermassive black holes, the high luminosity of an active galactic nucleus primarily consists of
A) light emitted by hot gas in an accretion disk that swirls around the black hole.
B) intense radiation emitted by the black hole itself.
C) the combined light of thousands of young, high-mass stars that orbit the black hole.
D) radio waves emitted from radio lobes found on either side of the galaxy we see in visible light.
A) light emitted by hot gas in an accretion disk that swirls around the black hole.
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Capacitors in Combination: A 2.0-?F capacitor and a 4.0-?F capacitor are connected in series across an 8.0-V potential source. What is the charge on the 2.0-?F capacitor?
A. 2.0 ?C B. 4.0 ?C C. 12 ?C D. 11 ?C E. 25 ?C
On an H-R diagram, a red supergiant would be located in the
A) upper right. B) upper left. C) lower left. D) lower right.
Imagine an advanced civilization living on a planet orbiting at a distance of 10 AU (1.5 billion kilometers) from a close binary star system that consists of a 15 MSun red giant star and a 10 MSun black hole. The black hole is surrounded by an accretion disk. Sometime within the next million years or so, the civilization's planet is likely to be doomed because
A) the red giant will probably supernova within the next million years. B) jets of material shot out of the accretion disk will shoot down their planet. C) the red giant star, which provides most of energy the civilization needs to exist, will soon be destroyed in the accretion disk. D) tidal forces from the black hole will rip the planet apart. E) the planet's orbit will gradually decay, as it is sucked in by the black hole.
Hubble's Law (also known as the Hubble-Lemaitre Law) can be restated as:
A. The mass-to-light ratio of a spiral galaxy is greater if its rotational velocity is also greater. B. The more distant a galaxy, the faster it is receding. C. The rotation curve of a galaxy is related to the amount of mass inside. D. The velocity curves of spiral galaxies only make sense if there exists a lot of unseen matter.