What causes X-ray bursters?
A) The binary companion of a neutron star spirals in and combines with the neutron star.
B) The mass of an accreting neutron star passes a critical threshold between 2 and 3 Msun and explodes.
C) Helium fusion, which occurs when the thin layer of accreted material on a neutron star reaches 100 million K
D) The rapid rotation of the neutron star causes it to fly apart.
Question 2
Objects in the Kuiper belt
A) are in random orbits at all inclinations to the ecliptic.
B) are the sources of long-period comets.
C) lie beyond the orbit of Neptune, and close to the ecliptic.
D) are dense, like the iron meteorites.
E) lie beyond the orbit of Neptune and perpendicular to the ecliptic.