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First Planet Known To Orbit a White Dwarf Is Falling Apart (nasa.gov)
schwit1 writes: It's virtually certain that some white dwarfs still have planets in orbit despite their violent histories, but seeing those planets has proven difficult... at least, until now. Astronomers using the Kepler space observatory have spotted a planet circling around WD 1145+017, a white dwarf 570 light years away. Not that it's in great shape, mind you. The unusual light signature (PDF) from the dying star hints that the planet is disintegrating under the star's gravitational pressure, leaving behind a giant dust cloud. Researchers suspect it fell into its fatal orbit after the star's rapid change in mass triggered a planetary collision.
You should see more discoveries like this in the future, since the weaker light of a white dwarf is less likely to obscure planets. There's even a chance (however small) that collisions have bumped some planets into habitable zones, giving scientists an unusually clear view of worlds that could support life. Either way, it's evident that planetary systems don't vanish simply because their host stars are running out of time.
You should see more discoveries like this in the future, since the weaker light of a white dwarf is less likely to obscure planets. There's even a chance (however small) that collisions have bumped some planets into habitable zones, giving scientists an unusually clear view of worlds that could support life. Either way, it's evident that planetary systems don't vanish simply because their host stars are running out of time.
The mass of the star has changed, in that perhaps half of its mass has been expelled into a planetary nebula. That expelled mass is beyond the planet's orbit, and the orbit of the planet is subsequently determined only by the remaining stellar mass. Also, that expelled mass is moving away from the remaining white dwarf, and is being diluted in interstellar space. I've forgotten enough college physics to be unable to say what the expected effect on the planet is due to the combined effects of the force of expulsion and the reduced mass of the central star on the planet's orbit should be (does it move in or out, etc).