Why is it thought that quasars probably spend only a fairly short time in their highly luminous phase?
A) because there aren't many quasars around today
B) because there aren't any quasars closer than about a redshift of 1
C) because all quasars are at about the same epoch, narrowly defined in time
D) because a black hole could not power a highly luminous quasar for more than a few million years
E) because quasars are known to be the consumers of massive galaxies
D
You might also like to view...
Current evidence suggests that the Universe is
a. flat, infinite, and neither expanding nor contracting. b. closed, finite, and slowing its expansion. c. open, infinite, and slowing in its expansion. d. static with no expansion. e. flat, infinite, and accelerating in its expansion.
The most detailed look we've had of an asteroid comes from
A) spacecraft sent to an asteroid. B) ground-based radar images. C) Earth orbital X-ray images. D) ground-based optical images. E) high-altitude UV spectroscopy.
A corner cube is formed by three plane mirrors perpendicular to one another resulting in a retroreflector. What is the angle between the directions of an incoming ray of light and of the corresponding outgoing ray of light for this device?
a. 90° b. 180° c. 0° d. 360°
In a single-slit diffraction experiment, the first minimum in the diffraction pattern occurs at an angle given by sin? = 2?/W
Indicate whether the statement is true or false