A planet that has outlived its star

Located 117 light-years from Earth, the star WD1054-226 is a white dwarf – the remnant of a star the size of our Sun that has reached the end of its life. It’s about the size of Earth, but about as heavy as the Sun. And it’s hot: 20,000 to 30,000 Kelvin on the surface, 20 million Kelvin inside. Fusion processes no longer take place, but it takes about 10 billion years for it to cool down completely – our sun has only been around for five billion years. During this time, of course, a habitable zo...