Episode 3 ( cosmos facts)

Lucy in the sky with diamonds.

A star in the constellation of Centaurus has a secret at its heart. At first it appeared to be a dim white dwarf, but it subsequently turned out to be incredibly dense, with the mass of the Sun crammed into an object only a third the diameter of Earth.

It is also remarkably cool, with a core temperature of a mere 6,600°C (by comparison, the Sun is around 15 million°C). At these temperatures stars begin to vibrate, and astronomers can use these vibrations to peer inside a star. In this case, they found that the star’s carbon core had crystallised to form a diamond 10 billion trillion trillion carats in size. The star was later nicknamed Lucy, after the Beatles song ā€˜Lucy in the Sky with Diamonds’.

Since the discovery of Lucy, several other crystallised stars have been found, some with diamond hearts the size of Earth.