For nearly 40 years astronomers had believed that the interiors of white dwarfs – the remnants of stars like our Sun – were crystallised carbon; that is to say, they were made of diamond. These would be truly enormous jewels – several thousand kilometres in diameter. It’s only in the last few years that clear evidence for these giant cosmic gems’ existence has been obtained.
Around 50 light years from Earth in the constellation of Centaurus is the compacted heart of a dead star with the technical name BPM 37093. It no longer shines, but it does still twinkle, as a 10 billion, quadrillion-carat diamond 4,000 kilometres (2,485 miles) in diameter. Its fascinating secret was uncovered because it resonates with regular frequency and, by measuring the pulsations, scientists were able to determine the composition of its interior. It’s a similar method to the way geologists can establish what’s underground using a seismograph.
Our Sun will reach its white dwarf stage in about 5 billion years’ time, crystallising over a further 2 billion years to become literally the jewel of our own Solar System.