Some 10 billion years from now, our sun will end its long life as a giant crystal ball. The same fate awaits most of the medium-sized stars in the Milky Way galaxy once they collapse into white dwarfs upon reaching the end of their life cycle.
The revelation comes from a new study on stellar death published yesterday in the journal Nature. The research shows that white dwarf stars go through a process of solidification once the hot gas within their core starts to cool down, eventually turning into solid crystal spheres.
The phenomenon is fairly similar to that of water freezing from liquid to ice; the difference is that white dwarf stars begin to crystallize after their interior cools down to about 18 million degrees Fahrenheit (10 million degrees Celsius), reveals the new study.
‘Crystal Spheres In The Sky’
“All white dwarfs will crystallize at some point in their evolution, although more massive white dwarfs go through the process sooner,” said study lead author Pier-Emmanuel Tremblay, a physicist at the University of Warwick in England.
“This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky. The sun itself will become a crystal white dwarf in about 10 billion years.”
His team arrived at this conclusion after analyzing data gathered by the European Space Agency’s (ESA) Gaia satellite. For the purpose of this study, the scientists examined observations on 15,000 white dwarfs located relatively close to the sun, on a distance range of maximum 300 light-years from our star.
“White dwarfs are the remains of medium-sized stars similar to our sun,” explains the ESA. As soon as these dead stars deplete all of their hydrogen reserves, they begin to shed their outer layers until they are reduced to a hot core, which then starts cooling down.
The result is an Earth-sized ball that is about 200,000 times denser than our planet. In fact, white dwarfs are so dense that a tiny portion of their core measuring no more than 1 cubic centimeter would weigh around 10 tons, details Science Alert. That’s the equivalent of a teaspoon of white-dwarf material weighing about as much as an elephant.
The Life Cycle Of Stars
According to a previous study published last year in Nature Astronomy, around 90 percent of the stars in the universe will end up as white dwarfs. As they arrive at the end of their active life, these stars — our sun included — will flare up into red giants and then crumble into white dwarfs, shortly after igniting as bright planetary nebulae, the Inquisitr reported at the time.
The Gaia observations unveiled that white dwarfs are in for a dazzling end. Once they cool down, these stellar remains begin a crystallization process — morphing into “cosmic jewels,” as described by Space.
While the idea itself is not a new one and was actually theorized about half a century ago, this is the first time that astronomers have gathered solid evidence, so to speak, that white dwarf stars solidify into crystals, notes Phys.org.
After pouring over the Gaia data, the team uncovered a strange pile-up of white dwarfs of certain colors and brightness levels. Although exhibiting the same features, these stars were not of the same age — neither did they evolve together to form a distinct population of white dwarfs.
This peculiar find could only be put down to the effects of white dwarf cooling and crystallization, explained Tremblay.
“This is the first direct evidence that white dwarfs crystallize, or transition from liquid to solid. It was predicted 50 years ago that we should observe a pileup in the number of white dwarfs at certain luminosities and colors due to crystallization, and only now this has been observed.”