White dwarf stars observed slowly crystallising and turning into solid spheres

White dwarf star in the process of solidifying

White dwarf star in the process of solidifying. Credit Dr Mark A. Garlick

Astronomers at the University of Warwick have found first direct evidence of white dwarf stars solidifying into crystals and our skies are filled with them.

"We could visualise crystallised white dwarfs as giant balls of solid oxygen and carbon, with only tiny amounts of other residual elements", Pier Emmanuel Tremblay, assistant professor of astronomy at Warwick who led the study, told The Telegraph. They are incredibly useful to astronomers as their predictable lifecycle allows them to be used as cosmic clocks to estimate the age of groups of neighboring stars to a high degree of accuracy. Using data from the ESA's Gaia satellite, an global group of researchers claim to have found evidence that supports the theory that when massive white dwarf stars like our brilliant host (the Sun) burn out and die, they solidify into metallic crystals. These observations mean that they are potentially billions of years older than astronomers previously thought.

A cross-section of a crystallized white dwarf star.

According to the team, they were able to find a large number of white dwarfs of specific colours and luminosities.

My assumption scientists build on the analysis of more than 15 thousand white dwarfs, distant from the Earth at a distance of 300 light years.

The oldest white dwarfs, nearly the age of the Milky Way, are likely to be almost fully crystal Discovery published in Nature exactly fifty years after it was predicted. You would just have to wait around for another 10 billion years to actually see it.

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If the stars did not crystallise they would cool at a steady rate, going from blue to orange to red and losing brightness along a smooth slope.

"We saw a pile-up of white dwarfs of certain colors and luminosities that were otherwise not linked together in terms of their evolution", said Tremblay. "The sun itself will become a crystal white dwarf in about 10 billion years". Before it begins to solidify and harden gradually, the sun will turn into a red giant, and from that moment it will begin to shrink down and turn into a white dwarf.

"Not only do we have evidence of heat release upon solidification, but considerably more energy release is needed to explain the observations", Tremblay said. Before Gaia we had 100-200 white dwarfs with precise distances and luminosities - and now we have 200,000.

Dr. Tremblay included that every single white dwarf will eventually crystallize, implying that "billions of white dwarfs in our universe have officially finished the procedure and are basically crystal spheres in the sky. This will push the carbon upward, and that separation will release gravitational energy".

The interior of a "crystal orb" white dwarf. "This experiment on an ultra-dense matter is something that simply can not be performed in any laboratory on Earth".

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