Not just white: some dying white dwarf stars glow pink and green

White dwarfs, the dense remnants of sun-like stars, can appear pink, green or even purple, astronomers report. A study in RAS Techniques and Instruments says density is key: in the coolest white dwarfs, trace elements like carbon, calcium and sodium interact with dense helium plasma and absorb a wider range of colours. Material from shattered asteroids and planets also shapes their hues.