1. The radius of a white dwarf is determined by a balance between the inward force of gravity and the outward push of . 2. A white dwarf in a close binary system will explode as a supernova if it gains enough mass to exceed the . 3. A(n) consists of hot, swirling gas captured by a white dwarf (or neutron star or black hole) from a binary companion star. 4. A(n) occurs when hydrogen fusion ignites on the surface of a white dwarf in a binary system. 5. A(n) can occur only in a binary system, and all such events are thought to have about the same luminosity. 6. A(n) occurs when fusion creates iron in the core of a star.