Simplify the following text for a Grade 10 native English-speaking person.
Original: novae ) is a cataclysmic nuclear explosion caused by the accretion of hydrogen on to the surface of a white dwarf star , which ignites and starts nuclear fusion in a runaway manner .
Simplified: A nova ( plural : novae ) is a nuclear explosion that occurs when gravity from a white dwarf star collects hydrogen from a neighboring star . This process starts nuclear fusion on the white dwarf , and a nuclear explosion results .