The white dwarf stars are defined as objects that are almost similar to the size of the Earth and their mass is equivalent to the sun. The materials that are present within the massive white dwarf cannot undergo any process of fusion reactions due to which they have an absence of energy source.
The density of these white dwarfs is roughly kg/m³, which is significantly very high. These are probably the most dense materials that are present in the universe. In order to study the white dwarf stars, the UV astronomy is generally used.