1. They can go supernova. Because many stars orbit others in relatively close proximity, a white dwarf in a binary system can begin to cannibalise its partner, pulling material away from it. The white dwarf continues to gobble up matter from the other star until eventually a critical mass is reached, triggering a chain reaction that results in the white dwarf violently exploding in a type Ia supernova.
2. Their gravity is 350,000x Earth’s. ‘Degenerate dwarfs’, as they’re otherwise known, no longer generate outward pressure via fusion like main-sequence stars, so their huge mass causes them to collapse and compact under gravity. The more mass a white dwarf has, the greater the gravity, the more its matter is compressed and, therefore, the smaller the dwarf is.
3. Many will become black dwarfs. A white dwarf is the core of a dead star and these stellar remnants gradually cool until they no longer radiate – in other words, they become more or less the same temperature as the background of space. At this point, they are considered ‘black dwarfs’. However, no black dwarfs exist yet because this process takes trillions of years, many times longer than the current age of our universe.
4. A teaspoon of white dwarf matter weighs 5.5 tons. White dwarfs are extremely dense objects. They have a radius that’s typically around 100 times smaller than our Sun, but have the same mass. As a result, just a single teaspoon of white dwarf matter would weigh as much as an elephant on Earth.
5. The Sun will one day become a white dwarf. The most massive stars will eventually go supernova, but stars will anything from 0.8 to about ten solar masses will ultimately become white dwarfs. This represents over 97 per cent of the Milky Way – most of the stars you can see in the night sky.