Billions of stars across space turning into enormous crystals, satellite data reveals

Even the Sun will crystallise over the course of 10 billion years

Billions of stars across space are turning into giant crystal spheres as their liquid cores slowly turn solid, astronomers have revealed.

The finding suggests traditional ways of measuring star age may have to be adjusted, as some could potentially be billions of years older that currently thought.

This shift was observed in thousands of white dwarfs – the remains of stars that have exhausted the nuclear fuel that keeps them burning.

Our own Sun will eventually succumb to this process, gradually solidifying over the course of about 10 billion years.

Astronomers had previously predicted that as white dwarfs cooled they underwent such a process, but until this point they had no evidence from direct observations of the stars.

But a new study, published in the journal Nature, provides such evidence, after the scientists collected data from 15,000 stars within 300 light years of the planet, mainly using the European Space Agency’s Gaia satellite.

They found a point at which the gradual cooling of these stars slowed down, a phenomenon they attributed to a massive release of heat that signalled a transition from liquid to solid.

The process, in which the sea of liquid oxygen and carbon in the star’s core transforms into a solid crystal, is something like the transition of liquid water into ice.

“It was predicted fifty years ago that we should observe a pile-up in the number of white dwarfs at certain luminosities and colours due to crystallisation and only now this has been observed,” said Dr Pier-Emmanuel Tremblay, an astronomer at the University of Warwick.

Unlike water becoming ice, this process takes place at incredibly high temperatures, as well as extreme pressures that pack the atoms very closely together.

As the white dwarf core cools to around 10 million C, the carbon and oxygen fluid begins to solidify.

Dr Tremblay said the heat energy release suggested by their results is likely a result of oxygen crystallising first, sinking to the bottom of the core and pushing carbon upwards.

The life cycles of white dwarfs – some of the oldest stars in the universe – are well understood, and are often used as a reliable tool to determine the age of nearby stars.

However, the lag in cooling the scientists revealed suggests some of these stars may be up to two billion years older than previous estimates.

“All white dwarfs will crystallise at some point in their evolution, although more massive white dwarfs go through the process sooner,” said Dr Tremblay. “This means that billions of white dwarfs in our galaxy have already completed the process and are essentially crystal spheres in the sky.”