What observational evidence suggests that the centers of quasars are small, about a fraction of a light-year?
A. photographs of quasars
B. the fact that quasars are so distant, and therefore are very young
C. They emit radiation over a very wide range of wavelengths
D. The intensity of their radiation fluctuates over periods of months
E. All of these choices are correct.
Answer: D
You might also like to view...
Uniform Circular Motion: One way that future space stations may create artificial gravity is by rotating the station. Consider a cylindrical space station 380 m in diameter that is rotating about its longitudinal axis. Astronauts walk on the inside surface of the space station. How long will it take for each rotation of the cylinder if it is to provide "normal" gravity for the astronauts?
A. 28 s B. 39 s C. 6.2 s D. 4.4 s
Generally speaking, a main-sequence star is ________ than it was during the time it was a protostar
A) hotter and dimmer B) hotter and brighter C) cooler and dimmer D) cooler and brighter
Sunspots increase and decrease periodically over a 15 year time span.
a. true b. false
If the distance between us and a star is doubled, with everything else remaining the same, its luminosity
A) is decreased by a factor of two, and its apparent brightness is decreased by a factor of two. B) remains the same, but its apparent brightness is decreased by a factor of four. C) is decreased by a factor of four, and its apparent brightness is decreased by a factor of four. D) remains the same, but its apparent brightness is decreased by a factor of two. E) is decreased by a factor of four, but its apparent brightness remains the same.