Which of the following is the double-degenerate model for Type Ia supernovae [soo-per-NOH-ve]?

W) The cores of a binary system undergo common envelope evolution collapse and explode after iron fusion

X) A red giant overflows its Roche [ROHSH] lobe and dumps matter onto a white dwarf until the white dwarf exceeds the Chandrasekhar [chun-druh-SAY-ker] mass

Y) Two white dwarfs collide to create a new object, which exceeds the Chandrasekhar mass

Z) A main sequence star overflows its Roche lobe and dumps matter onto a white dwarf until the white dwarf exceeds the Chandrasekhar mass
Y) TWO WHITE DWARFS COLLIDE TO CREATE A NEW OBJECT, WHICH EXCEEDS THE CHANDRASEKHAR MASS