What are stars made of?
A: Gases, primarily Hydrogen, then Helium
B: Nothing but light and energy
C: Trick question- we really don't know
D: Pretty much the same as Earth, but with a special shell
E: They're fireflies stuck in the big blue/black thing
Ans: A: Gases, primarily Hydrogen, then Helium
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In the context of black holes, if an object collapses to zero radius, its density and gravity _____
A) remain constant B) increase C) become infinite D) decrease
All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
A) Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet. B) Venus has many circular features, called coronae, which appear to be tectonic in origin. C) Venus's largest features are three elevated regions that look somewhat like continents. D) Venus appears to lack any water that could lubricate the flow of rock in its crust and mantle.
Suppose you read somewhere that 10 percent of the matter in the Milky Way is in the form of dust grains. Should you be surprised? If so, why?
A) Given how easily dust grains can form, 10 percent is a surprisingly low fraction. B) The fraction of 10 percent is surprisingly high because dust grains can form only at low temperatures. C) There is nothing surprising about the 10 percent figure because dust grains are the material from which stars are born. D) The fraction of 10 percent cannot be correct. Dust grains are solid and only 2 percent of the matter in the galaxy is made of anything besides hydrogen and helium.
The proton-proton chain needs high temperature because
a. of the ground state energy of the hydrogen atom. b. of the presence of helium atoms. c. the protons must overcome the Coulomb barrier. d. of the need for low density. e. the neutrinos carry more energy away than the reaction produces.