What happens to its planets when a star become white dwarf?

It is possible,

if the planet survives the red giant phase

and is far enough away from its host star.

A white dwarf's gravity is much weaker than its

former self as a yellow dwarf.

Recently large planets have been discovered

wandering the galaxy

and scientist estimated that

they could be rather common.

check out the link.

Edit:

for all those that know " little " about stellar evolution,

and the variation of the gravity of a dying star.

i.e. "Alladin" and "Billy Butthead"

If you insist the force of gravity doesnt decrease

as a star evolves from main sequence

to red giant and then to white dwarf phase.

check out the second link.

.

Unless the star exploded in a supernova (in which case the planets would be destroyed), the planets only become colder and darker. That's it. Most stars do not go supernova and explode - they expand and then contract into Dwarfs. Just as our sun will do. Mercury, Venus, and probably Earth will be consumed when the sun expands, but the asteroids and other planets will not. The mass of the resulting White Dwarf when the sun contracts will be the same as the mass before it became a White Dwarf. And that means the gravity will still be exactly the same. And that means the planets will still revolve in their same orbits.

.

new planets might form from the ejected mass, what little remains of the system that was once there, and any stuff that happens to drift in. In fact, planet hunters now are saying that white dwarfs might be a very good place to look around for habitable planets; they're not as violent as living stars. So, something like that might happen to the Sun.

Some planets may get consumed by the star when it's in the red giant/supergiant stage and the rest will orbit the white dwarf.

No... Witch ever has the greatest force will group as many as can together and it will go like that thell find a new group of planets and then soon wander into a sun, but most likely when the white dwarf implodes it will most likely destroy the plNets in system

It maintains it's gravitational field but it expands first and vaporizes it's inner planets the others all freeze up it they weren't in the first place.