However, the death of a red dwarf and its subsequent transformation into a white dwarf does not mark the end of its evolutionary journey. Over the course of billions of years, the stellar husk continues to bleed heat, until the core finally cools to around 10 million °C.
The crystal spheres are made of carbon and oxygen under such high density their crystal structure will make them appear to be like a metal - although it is possible that diamonds may also form as the star cools.
The result is likely a core composed of crystallized oxygen and a mantle dominated by carbon.
The crystallization process would dramatically slow the cooling process, theoretically prolonging the life of a star by as much as 2 billion years.
This crystallization process was first predicted by Hugh Van Horn, a theoretical astrophysics professor at the University of Rochester in America some fifty years ago.
The first direct evidence of white dwarf stars solidifying into crystals has been discovered by astronomers at the University of Warwick, and our skies are filled with them.
The team in Warwick studied 15,000 white dwarf candidates within around 300 light years of Earth and measured their colour and luminosity for clues about their composition.
Tremblay and his colleagues analyzed data gathered by the European Space Agency's Gaia spacecraft, which launched in December 2013 to help researchers construct the best-ever 3D map of the Milky Way. The data found a "pile-up", or a rather larger number of white dwarfs with "specific colors and luminosities that do not correspond to any single mass or age".
According to the authors of the new paper, the release of heat energy alone would not be enough to account for their observations. "This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky". "We realized that this was not a distinct population of white dwarfs, but the effect of the cooling and crystallization predicted 50 years ago". So understanding this crystallization process could bring greater accuracy when scientists assign ages to the stars.
"All white dwarfs will crystallize at some point in their evolution, although more massive white dwarfs go through the process sooner", said Dr. Tremblay.