The narrowness of the rings of Uranus and Neptune is believed to be caused by
a. gravitational interactions between ring particles.
b. a spiral density wave which confines them.
c. the magnetic field which holds them in place.
d. the smaller mass of Uranus and Neptune as compared to that of Saturn.
e. small shepherd moons that orbit near the rings.
E
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Which of the following could not be measured by an observation that uses only imaging?
A) the rate at which a variable star brightens and dims B) the general shape of an interstellar cloud of gas C) the color of a planet D) the brightness of a star in our sky E) the number of bright stars in a nearby star cluster
The Sun projects charged particles into space, giving rise to a flow of radiation called the
a. heliosphere. b. solar wind. c. corona. d. chromosphere.
The Pleistocene is a(n)
a. epoch. b. era. c. eon. d. period.
What did most Greek philosophers accept as a first principle? a. Earth was the unmoving center of the Universe. b. The heavens are imperfect
c. The tetrahedron is the perfect geometric form. d. There are only six planets in the Universe. e. Earth travels on an elliptical orbit.