As of early 2013, the number of confirmed exoplanets found was:
A) 5, all around stars within 20 light years of us.
B) 42, all much bigger than Jupiter, but orbiting red dwarf stars.
C) over 400, orbiting more than 300 stars.
D) about 900, mainly around stars much smaller and fainter than our Sun.
E) thousands, around every star we have closely examined to date.
D
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Presuming that it takes several billion years of complex live to evolve in a stable environment, the stars most likely to currently have inhabited planets are
a. G to K main sequence stars. b. B to A main sequence stars. c. G to K giants. d. white dwarf stars e. neutron stars.
If an object has a multiplicity ? that decreases as its thermal energy U increases, its temperature would
A. be always zero. B. be always positive (and nonzero). C. be negative (and nonzero). D. increase as U increases. E. decrease as U increases
What evidence do we have that Earth's magnetic field reverses its polarity every 250,000 years?
A. Earth's magnetic field strength and direction change constantly. B. The direction of the magnetic field is "frozen" into new crust as it cools. C. historical documents from ancient Egypt and other civilizations D. Core samples from Antarctica show a regular change in polarity. E. All of these choices are correct.
In the case of constant acceleration, the average velocity equals the instantaneous velocity:
a. at the beginning of the time interval. b. at the end of the time interval. c. half-way through the time interval. d. three-fourths of the way through the time interval.