Answer:
A typical white dwarf is as massive as the Sun but only about as large in size as Earth.
Explanation:
The final stages of stars depend on its mass. For the case of a star like the Sun, it fuses hydrogen into helium in its core, that nuclear fusion brings, as a result, a radiation pressure that counteracts the gravitational force that goes inward as a consequence of its own mass. Hence, the star will be in hydrostatic equilibrium (spherical shape) when the two forces balanced each other.
When the hydrogen fuel runs out, the layers of the sun will start to collapse by means of the gravity, since there is not equilibrium. However, that collapse increases the nucleus temperature which allows helium to fuse in heavier elements. The suddenly nuclear reaction expands the layers again in a violent way.
The expansion of the gas drops its temperature, which leads to the change in color for red, and therefore, it will become a red giant star.
Once the star is in this red giant phase, it will reach a point in which the helium fuel runs out too, so the superficial layers will collapse again until this gravitational force will be counteracted by the pressure of degenerate electrons, then, a white dwarf is gotten.
all that it was discussed in the last paragraph leads to the result that the mass will be concentrated in a smaller radius, then, white dwarfs have high densities.
