76) The outward pressure in the core of a red : 1828919
76) The outward pressure in the core of a red giant balances the inward pull of gravity when
A) the electron orbits are compressed so much they are all in contact.
B) the electrons and protons have combined to form neutrons.
C) hydrogen begins fusing into helium.
D) carbon fuses into heavier elements.
E) iron forms in the inner core.
77) Which of these is true of planetary nebulae?
A) They are expelled by the most massive stars in their final stages before supernova.
B) They are rings of material around protostars that will accrete into planets in time.
C) They are ejected envelopes surrounding a highly evolved low-mass star.
D) They are the envelopes that form when blue stragglers merge.
E) They are the material which causes the eclipses in eclipsing binary systems.
78) Compared to our Sun, a typical white dwarf has
A) about the same mass and density.
B) about the same mass and a million times higher density.
C) a larger mass and a hundred times lower density.
D) a smaller mass and half the density.
E) a smaller mass and twice the density.
79) A(n) ________ represents a relatively peaceful mass loss as a red giant becomes a white dwarf.
B) emission nebula
C) supernova remnant
D) planetary nebula
80) A surface explosion on a white dwarf, caused by falling matter from the atmosphere of its binary companion, creates what kind of object?
C) gamma ray burstar
D) Type I supernova
E) Type II supernova
81) Which of these evolutionary paths is the fate of our Sun?
A) brown dwarf
B) supernova of Type II
D) planetary nebula
82) When the outer envelope of a red giant escapes, the remaining carbon core is called a
A) black dwarf.
B) white dwarf.
C) planetary nebula.
D) black hole.
E) brown dwarf.
83) The initial mass of a protostar generally determines the star's future evolution. But in some cases, what can alter this process?
A) The star may be isolated in space, far from other influences.
B) The star may be in a spectroscopic binary system.
C) The star may gain mass by passing through a dark cloud.
D) The star may collide with another, unrelated star.
E) The star may drift away from the other stars in its formation cluster.
84) Black dwarfs are
A) very common, making up the majority of the dark matter in the universe.
B) often made from very low mass protostars that never fuse hydrogen.
C) rare, for collapsing cores of over three solar masses are uncommon.
D) rare, for few binary systems are close enough for this merger to happen.
E) not found yet; the oldest, coldest white dwarf in the Galaxy has not cooled enough yet.
85) Virtually all the carbon-rich dust in the plane of the galaxy originated in
A) low-mass stars.
B) high-mass stars.
C) planetary nebulae.
D) white dwarfs.
E) brown dwarfs.