Billions of years from now our dead Sun will solidify into a giant crystal ball, a new study suggests.
Most stars entering the final chapter of their lives tend to shrink, wither and slowly turn white. Astronomers call these cold, dense objects white dwarfs.
As detailed in a paper published on Wednesday in Nature, astronomers at the University of Warwick in the UK obtained the first direct evidence of a star’s core turning into a crystal of solid oxygen and carbon. These crystal balls fill our skies.
The discovery, led by Dr. Pier-Emmanuel Tremblay from the University of Warwick’s Department of Physics, has been published in Nature. It is largely based on observations taken with the European Space Agency’s Gaia satellite.
Half a century ago, theorists predicted that white dwarfs solidify into crystal over time. But the new research has found that this is indeed the case.
“All white dwarfs will crystallize at some point in their evolution, although more massive white dwarfs go through the process sooner,” study lead author Pier-Emmanuel Tremblay, a physicist at the University of Warwick in England, said in a statement.
“This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky,” Tremblay added. “The sun itself will become a crystal white dwarf in about 10 billion years.”
White dwarfs are the remaining cores of red giants after these huge stars have died and shed their outer layers. They are constantly cooling as they release their stored up heat over the course of billions of years.
Gaia and the Cosmic Crystals
So, for this study, Tremblay and his colleagues used observations from the European Space Agency’s Gaia satellite. Therefore, they analyzed the luminosity and colors of about 15,000 known white dwarfs located within 300 light-years of Earth.
They identified an excess in the number of stars at specific colors and luminosities. It turns out they do not correspond to any single mass or age. The uniform appearance of these stars suggested that the dwarfs had reached some sort of set phase in their development, and one that could span billions of years. When compared to evolutionary models of stars, the pile-up strongly coincides to the phase in their development in which latent heat, scientists predict, will be released in large amounts. Thus, resulting in a slowing down of their cooling process. When a white dwarf cools enough, the molten liquid at its core begins to solidify. This means the star begins turning to crystal.
“This is the first direct evidence that white dwarfs crystallize or transition from liquid to solid,” Tremblay said.
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Scientists estimate that in some cases these stars have slowed down their aging by as much as 2 billion years, or 15 percent of the age of our galaxy.
So, many white dwarfs may be billions of years older than previously calculated.
“Not only do we have evidence of heat release upon solidification, but considerably more energy release is needed to explain the observations,” Tremblay added. “We believe this is due to the oxygen crystallizing first and then sinking to the core, a process similar to sedimentation on a river bed on Earth. This will push the carbon upwards and that separation will release gravitational energy.”
However, there’s no need for humans to worry about our own space crystal blinding us. The Sun’s explosion will destroy Earth long before it begins to crystallize.
Thumbnail image: An artist’s rendering of a white dwarf undergoing crystallization. Image: University of Warwick/Mark Garlick