The two white dwarf stars orbit so close together that the whole system could fit inside the planet Saturn. (Credit: Caltech/IPAC)

Astronomers using the Zwicky Transient Facility at Kitt Peak in Arizona have discovered the second fastest orbiting pair of white dwarfs. At the end of their normal lives, our sun and other stars like it become white dwarfs. Their outer layers puff away and leave behind a hot, dense core. And if those stars started life in a binary pair, as most stars do, then th