* Novas don't destroy the star: Novas are powerful explosions that occur on the surface of a white dwarf star. The white dwarf itself survives the explosion.
* White dwarfs are the leftover cores of stars: A white dwarf is the dense, hot remnant of a star that has exhausted its nuclear fuel.
* The nova is fueled by accretion: The nova happens when a white dwarf in a binary star system accretes (pulls in) matter from its companion star. This accretion builds up a layer of hydrogen on the white dwarf's surface, eventually reaching a critical mass.
* Thermonuclear runaway: The hydrogen layer ignites in a thermonuclear runaway reaction, causing a powerful explosion that we see as a nova.
In short, a nova is a powerful explosion on the surface of a white dwarf, not its destruction. The white dwarf remains after the nova, albeit slightly heavier from the accreted material.
Important Note: There are also supernovas which are much more powerful explosions than novas and can destroy the star completely. A supernova is a result of a different process than a nova, and typically involves either a white dwarf exceeding a certain mass limit or a massive star collapsing under its own gravity.
