The average distance between stars in the neighborhood of the Solar System is about ________.
A. 4 AU
B. 4 kiloparsecs
C. 4 light-years
D. 4 arc seconds
Answer: C
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If a nuclear fission reactor produces an average power of 1.0 GW over the course of a year,
what mass of 235U is used up for a 365-day year if 200 MeV are released per fission reaction? (1 eV = 1.60 × 10-19 J, mneutron ? mproton = 1.67 × 10-27 kg) A) 0.35 kg B) 3.3 × 108 kg C) 1.1 × 108 kg D) 390 kg E) 1.75 kg
As discussed in the Extraordinary Claims box, when the giant impact idea was first proposed, it was generally thought to be so unlikely that it wasn’t seriously considered until decades later, after the Apollo missions to the Moon. What key piece of scientific understanding was missing that made it seem so unlikely when first proposed?
a. An understanding of the number and size of leftover planetesimals in the early solar system. b. An understanding of how heavily cratered the Moon’s surface is. c. A precise age for the solar system. d. An understanding of the difficulty of gravitationally capturing a body as large as our Moon.
What is the most common class of star in our galaxy?
A) G-type B) O-type C) M-type D) A-type
The Valles Marineris is ________ on the surface of Mars.
A. a long scarp B. a large volcano C. a 4,000-km canyon D. an old riverbed