The results of statistical studies of the exoplanet systems discovered to date suggests that what proportion of stars are likely to have a planet less than half the size of the Earth and in an orbit within a star's habitable zone?
A) 10 to 20%
B) 50%
C) much less than 10%
D) more than 90%
A
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The H-R diagram of a young star cluster shows
a. that high mass stars have not yet reached the main sequence yet. b. that low mass stars have not yet reached the main sequence yet. c. mainly giant stars. d. no stars since none have reached the main sequence yet.
The "close encounter hypothesis" suggested that the planets formed after a near-collision between our Sun and another star. If this hypothesis were correct, which of the following would be true?
A) Planetary systems would be very rare. B) Planetary systems would be very common. C) Most planetary systems would have their jovian planets closer to their stars and their terrestrial planets farther from their stars. D) Most planetary systems would have the same number of planets as our own. E) All planetary systems would be at least 4 billion years old.
Electric dipoles always consist of two charges that are
A) equal in magnitude; opposite in sign. B) equal in magnitude; both are negative. C) equal in magnitude; both are positive. D) unequal in magnitude; opposite in sign. E) unequal in magnitude; both are negative.
A thin lens of focal length 12.5 cm has a 5.0 cm tall object placed 10 cm in front of it. What is the size and orientation of the image?
A. 4.0 cm, inverted B. 4.0 cm, upright C. 8.9 cm, inverted D. 8.9 cm, upright E. 25 cm, upright