* Much smaller: A white dwarf is about the size of the Earth, while its progenitor star could have been much larger, even the size of our Sun.

* Much denser: A white dwarf packs the mass of a star into a much smaller volume. A teaspoonful of white dwarf material would weigh several tons on Earth.

* No longer fusing: A white dwarf is the burnt-out core of a star that has exhausted its nuclear fuel. It no longer undergoes nuclear fusion and emits light due to residual heat from its past fusion activity.

* Colder: A white dwarf slowly cools over time, eventually becoming a black dwarf (a theoretical object that hasn't been observed yet).

* Mostly composed of degenerate matter: The electrons in a white dwarf are packed so tightly that they behave like a single entity, resisting further compression.

* Can be incredibly hot: Although they are cooling, white dwarfs can have surface temperatures of tens of thousands of degrees Celsius.

In short, a white dwarf is the remnant of a star that has died, a much smaller, denser, and cooler object that no longer produces energy through fusion.