In a white dwarf, electrons are packed in so tightly that they physically cannot get any closer to one another. this provides an overall outward force, similar to the white dwarf’s thermal pressure but much stronger, called electron degeneracy pressure, which does not depend on the temperature of the material. a white dwarf no longer has any ongoing energy production from nuclear fusion, so it will continuously cool off with time. taking into consideration all the forces acting on each piece of the white dwarf, what will happen to it as it cools?

The white dwarf will start to get darker.

Explanation:

The white dwarf will keep is spherical shape, since electron degeneracy pressure (outward direction) will counteract the force of gravity due to its own mass (inward direction) which lead to hydrostatic equilibrium.

A nuclear reaction occurs when light elements combine into heavier elements (that is know as nucleosynthesis). Exist different ways in which that can happen, but the most common is the Proton-Proton chain. In that fusion reaction, two atoms of Hydrogen combine to form helium, while the fusion takes place, photons are created.

Photons are the elementary particles that constitute light and taking into account that in white dwarfs the production of photons has ceased because there are no nuclear fusions, then, it is clear that the white dwarf will start to get darker as it cools since is emitting into space the photons produced in the past.