Our sun ‘is going to turn into a crystal sphere’

Rodiano Bonacci
Gennaio 11, 2019

The twinkling orb may look similar to the other fiery stars around it, but it is actually a flawless sphere of crystal. Astronomers from the University of Warwick say they've found the first direct evidence that white dwarf stars - the dense, stellar corpses of stars like our sun - can crystallize, or turn from a liquid into a solid.

And there are billions of similar sparkling crystal spheres in the Milky Way alone.

"Previously, we had distances for only a few hundreds of white dwarfs and many of them were in clusters, where they all have the same age", said Pier-Emmanuel Tremblay, lead author of the study and an assistant professor at the University of Warwick.

Eventually white dwarfs cool down into black dwarfs when they give off no more heat. Now, a team of researchers have finally found observed these stellar remnants by digging into data collected by the European Space Agency's Gaia spacecraft. "We realized that this was not a distinct population of white dwarfs, but the effect of the cooling and crystallization predicted 50 years ago".

Scientists trained the Gaia space telescope on 15,000 white dwarf candidates within around 300 light years of Earth.

Dr. Tremblay added that all white dwarfs will eventually crystallize, meaning that "billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky". These data revealed an odd "pileup" - an overabundance of white dwarfs with certain colors and brightnesses that can not be explained by the objects' ages or masses.

Further analysis and modeling suggested that the odd "pile-up" is due to the crystallization process. The process really kicks into gear when a white-dwarf interior cools down to about 18 million degrees Fahrenheit (10 million degrees Celsius), the researchers said. The core is then formed of a crystallized metallic oxygen interior, with a carbon enhanced mantle.

"Not only do we have evidence of heat release upon solidification, but considerably more energy release is needed to explain the observations", Tremblay said. "This will push the carbon upwards, and that separation will release gravitational energy". The discovery was published Wednesday in the journal Nature.

Astronomers had long suspected such crystallization was possible.

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