Huge gravity of these dense stars, which have burned all their own fuel, rips apart smaller planetary bodies
It’s the end of the world, not quite as we know it.
Scientists from the University of Warwick and other universities have studied the impact white dwarfs – end-of-state stars that have burned all their fuel – have on planetary systems such as our own solar system.
When asteroids, moons and planets get close to white dwarfs, their huge gravity rips these small planetary bodies into smaller and smaller pieces, which continue to collide, eventually grinding them into dust.
While the researchers said Earth would probably be swallowed by our host star, the sun, before it becomes a white dwarf, the rest of our solar system, including asteroids between Mars and Jupiter, as well as moons of Jupiter, ultimately may be shredded by the sun in a white star form.
Two problems with your theory, that added mass is ejected as a planetary nebula prior to becoming a white dwarf. A considerable amount of mass is lost this way. Secondly the earth, venus, mars, and mercury together don’t even have a percent of a percent of the solar mass. The sun is ~332,000x more massive than the earth. The mass from eating up those planets will be a rounding error.