Complex sentence: A white dwarf undergoes carbon detonation only if it has a normal binary star companion close enough for the dwarf star to siphon sufficient amounts of matter onto itself, expelled during the process of the companion's own late stage stellar evolution.
Split into simpler sentences: A white dwarf undergoes carbon detonation only if it has a normal binary star companion close enough for the dwarf star to siphon sufficient amounts of matter onto itself. The siphoned matter having been expelled during the process of the companion's own late stage stellar evolution.