________ is the thermonuclear fusion of hydrogen to form helium operating in the cores of massive ...

________ is the thermonuclear fusion of hydrogen to form helium operating in the cores of massive stars on the main sequence.
 
  a. The CNO cycle
  b. The proton-proton chain
  c. Hydrostatic equilibrium
  d. The neutrino process
  e. None of the above

Question 2

Which of the following can't be associated with the spiral arms of a galaxy?
 
  a. dust and gas
  b. metal-poor stars
  c. young, massive stars
  d. star formation

Question 3

The lower edge of the main-sequence band is known as ________ and represents the location in the H-R diagram at which stars begin their lives as main-sequence stars.
 
  a. the Coulomb barrier
  b. hydrostatic equilibrium
  c. the birth line
  d. the zero-age main sequence
  e. the evolutionary track

Question 4

Sgr A is believed to be the center of the Milky Way galaxy because I. it lies in the general direction of the center of the galaxy based on observations of globular clusters in the plane of the Milky Way. II. long-wavelength dust-penetrating images show it to be a region crowded with stars. III. orbits of stars around it indicate a mass several million times that of the Sun within a volume a few light hours in size. IV. radio observations show it is a concentrated source at the center of swirling clouds of gas.
 
  a. I & II only
  b. II & III only
  c. I & IV only
  d. II & IV only
  e. All of I, II, III, & IV