10 January 2019
For the first time, astronomers have direct evidence of white dwarf stars solidifying into crystals – fifty years after the discovery was first predicted.
Astronomers have observed that the skies are filled with these white dwarfs that crystallise – and in fact the oldest white dwarfs, nearly the age of the Milky Way, are likely to be almost completely crystallised.
Our own Sun is destined to become a crystal white dwarf in about 10 billion years.
Lead author Dr Pier-Emmanuel Tremblay, from the University of Warwick, said: “This is the first direct evidence that white dwarfs crystallise, or transition from liquid to solid.
“All white dwarfs will crystallise at some point in their evolution, although more massive white dwarfs go through the process sooner. This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky.”
White dwarf stars are some of the oldest stellar objects in the universe. They are the remaining cores of red giants after these huge stars have died and shed their outer layers and they release their stored-up heat over the course of billions of years.
The astronomers selected 15,000 white dwarfs that were within 300 lightyears of Earth from observations made by the European Space Agency’s Gaia satellite and analysed them. They noticed that lots of the stars were the same colour and brightness, despite being different sizes and ages, and this was because these stars had started to crystallise – turn from liquid to solid.
STFC funds the exploitation of the data coming from the GAIA mission by UK astronomers.
More information available on the Warwick website.
Last updated: 15 January 2019