The material that accretes onto a neutron star or black hole is expected to emit X-rays because
a. the material will produce synchrotron radiation.
b. hydrogen nuclei begin to fuse and emit high energy photons.
c. the material will become hot enough that it will radiate most strongly a X-ray wavelengths.
d. as the material slows down it converts thermal energy to gravitational potential energy.
e. none of the above
C
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The proton-proton chain
a. combines two hydrogen nuclei to produce a single helium nucleus and energy. b. splits a helium nucleus to produce 4 hydrogen nuclei and energy. c. is the mechanism that increases the temperature between the photosphere and corona of the sun. d. is the interactions between protons in Earth's atmosphere that produces auroras. e. produces energy in the core of the sun in the form of gamma-rays, positrons, and neutrinos.
A company that produces pulsed gas heaters claims their efficiency is approximately 90%. If an engine operates between 250°C and 25°C, what is its maximum thermodynamic efficiency?
A. 83% B. 65% C. 43% D. 90% E. 56%
Which of the following statements about the rings of the four jovian planets is not true?
A) All rings lie within two to three planetary radii of their planet. B) All the particle orbits are fairly circular and near their planet's equatorial plane. C) All have gaps and ringlets. D) All probably look much the same as they did when the solar system first formed. E) All are made of individual particles of rock or ice that orbit in accord with Kepler's laws: inner ring particles orbiting faster, and outer ring particles orbiting slower.
Which of the following statements is true of the third reaction in the proton-proton chain?
A) It yields a helium atom. B) It emits a neutrino. C) It emits a gamma ray. D) It yields carbon dioxide.